This PDF file contains the front matter associated with SPIE Proceedings Volume 8012, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

Sofradir is one of the leading companies that develop and produce infrared detectors. Space applications have become a significant activity and Sofradir relies now on 20 years of experience in development and production of MCT infrared detectors of 2^nd and 3^rd generation for space applications. Thanks to its capabilities and experience, Sofradir is now able to offer high reliability infrared detectors for space applications. These detectors cover various kinds of applications like hyperspectral observation, earth observations for meteorological or scientific purpose and science experiments. In this paper, we present a review of latest Sofradir's development for infrared space applications. A presentation of Sofradir infrared detectors answering hyperspectral needs from visible up to VLWIR waveband will be made. In addition a particular emphasis will be placed on the different programs currently running, with a presentation of the associated results as they relate to performances and qualifications for space use.

A new airborne thermal infrared imaging spectrometer, "Mako", with 128 bands in the thermal infrared covering 7.8 to 13.4 microns, has recently completed its engineering flight trials. Results from these flights, which occurred in September 2010 and included two science flights, are presented. The new sensor flies in a Twin Otter aircraft and operates in a whiskbroom mode, giving it the ability to scan to ±40° around nadir. The sensor package is supported on a commercial 3-axis-stabilized mount which greatly reduces aircraft-induced pointing jitter. The internal optics and focal plane array are operated near liquid helium temperatures, which in conjunction with a fast f/1.25 spectrometer enables low noise performance despite the sensor's small (0.55 mrad) pixel size and the high frame rate needed to cover large whisk angles. Besides the large-area-coverage scan mode (20 km² per minute at 2-meter GSD from 12,500 ft. AGL), the sensor features a scan mirror pitch capability that enables both a high-sensitivity mode (longer integration times using frame summing, covering a smaller spatial region) and a multiple-look mode (multiple looks at a smaller region in a single aircraft overpass, for discriminating plume motion, for example).

Over the last decade SCD has established a state of the art VO_x μ-Bolometer product line. Due to its overall advantages this technology is penetrating a large range of systems. In addition to a large variety of detectors, SCD has also recently introduced modular video engines with an open architecture. In this paper we will describe the versatile applications supported by the products based on 17μm pitch: Low SWaP short range systems, mid range systems based on VGA arrays and high-end systems that will utilize the XGA format. These latter systems have the potential to compete with cooled 2^nd Gen scanning LWIR arrays, as will be demonstrated by TRM3 system level calculations.

For long ranging imaging in high performing electro-optical systems visible cameras with HDTV resolution (1920x1080) are becoming the standard sensor for observation purposes during day. During night and for thermal imaging, significant reduced resolution has to be accepted over a long period of time due to non-availability of adequate infrared detectors. In the meantime standard detectors with 1280x1024 are available on the market which provide at least SXGA resolution. ATTICA M is the newest member of Carl Zeiss Optronics ATTICA family of cooled thermal imagers, which uses an infrared detector with 1280x1024 pixels. ATTICA M can operate with a variety of infrared detectors either based on InSb or MCT as a detector material. ATTICA M is form and fit to the well known ATTICA Z and ATTICA P which is integrated in several military platforms in series production and can consequently be used to upgrade the related platforms. In detail three variants with different zoom optics covering the field of view range between 1,4° - 30° are available for a large scope of applications, on land, on the sea or in the air. A newly developed video electronic is capable to operate the Megapixel detector as well as future dual band thermal imager detectors as soon as they are available on the market. The features and options are discussed as well as the performances compared to the current thermal imager generation.

SWIR imagers can operate at near room temperature with cut-off wavelengths that extended from 1.7μm (for InP lattice matched InGaAs) to beyond 2.0μm with strained InGaAs epitaxial growth on InP substrate. A leading application in the SWIR band - Night vision, requires very low dark current levels, whereas the dark current increases as the cutoff wavelength increases. We demonstrate imaging applications made possible by utilization of dark current reduction, and the physics of background and objects radiance. A newly built imager is presented.

Knowledge regarding the processes involved in blasts and detonations is required in various applications, e.g. missile interception, blasts of high-explosive materials, final ballistics and IED identification. Blasts release large amount of energy in short time duration. Some part of this energy is released as intense radiation in the optical spectral bands. This paper proposes to measure the blast radiation by a fast multispectral radiometer. The measurement is made, simultaneously, in appropriately chosen spectral bands. These spectral bands provide extensive information on the physical and chemical processes that govern the blast through the time-dependence of the molecular and aerosol contributions to the detonation products. Multi-spectral blast measurements are performed in the visible, SWIR and MWIR spectral bands. Analysis of the cross-correlation between the measured multi-spectral signals gives the time dependence of the temperature, aerosol and gas composition of the blast. Farther analysis of the development of these quantities in time may indicate on the order of the detonation and amount and type of explosive materials. Examples of analysis of measured explosions are presented to demonstrate the power of the suggested fast multispectral radiometric analysis approach.

A remote infrared spectroscopy (RIRS) detection system was assembled using a mid infrared (MIR) Fourier Transform interferometer useful in open-path (OP) mode, a reflective infrared telescope and a cryocooled wide band, MCT detector. The system was used for passive mode IR thermal emission measurements and was also coupled to another Newtonian telescope in conjunction with a globar source for active mode measurements. The operation of the system was validated by measuring RIRS spectra of gases (NH₃) and condensable vapors: acetone, dichloromethane, methyl ether and acetonitrile. Solid samples were measured by smearing small amounts on aluminum plates after dissolving in appropriate solvents. Highly energetic compounds: TNT, DNT, PETN and RDX were also detected. Experiments of solids on metal surfaces were carried out in passive and active modes. The analyzed samples were placed at different standoff distances up to a maximum of 30 m in active mode and 60 m in passive mode.

The aim of this paper is to describe the progress and results of an imaging system designed to optimise the performance of human operator tasks through exploitation of multimodal sensors and scene context. The performance of tasks such as surveillance, target detection and situational awareness is dependent on the scene content, the sensors available and the algorithms deployed. Intelligent analysis of the scene into contextual regions allows specific algorithms to be optimised and appropriate sensors to be selected, thereby increasing the performance of the operator's tasks. Context-specific algorithms, which will adapt as the scene changes, are required. In the case discussed in this paper, the contextual regions include road, sky and vegetation, and the dynamic detection of each region utilises different sensor modalities. The paper will describe the overall system concept and a real-time imaging demonstrator using GPUs, which will be used for future demonstrations of the context-specific processing. Simulations of the context-specific scene analysis will be described using sensor data from a vehicle in a rural environment. The performance of a motion detection system with and without context will also be illustrated using measured image data.

Recent advances in micro-optical element fabrication using gray scale technology have opened up the opportunity to create simultaneous multi-spectral imaging with fine structure diffractive lenses. This paper will discuss an approach that uses diffractive optical lenses configured in an array (lenslet array) and placed in close proximity to the focal plane array which enables a small compact simultaneous multispectral imaging camera [1]. The lenslet array is designed so that all lenslets have a common focal length with each lenslet tuned for a different wavelength. The number of simultaneous spectral images is determined by the number of individually configured lenslets in the array. The number of spectral images can be increased by a factor of 2 when using it with a dual-band focal plane array (MWIR/LWIR) by exploiting multiple diffraction orders. In addition, modulation of the focal length of the lenslet array with piezoelectric actuation will enable spectral bin fill-in allowing additional spectral coverage while giving up simultaneity. Different lenslet array spectral imaging concept designs are presented in this paper along with a unique concept for prefiltering the radiation focused on the detector. This approach to spectral imaging has applications in the detection of chemical agents in both aerosolized form and as a liquid on a surface. It also can be applied to the detection of weaponized biological agent and IED detection in various forms from manufacturing to deployment and post detection during forensic analysis.

Flocks of migratory birds are very often using geographic structures like rivers, valleys or coast lines for orientation. Wherever the preferred migration routes are crossing the approach corridor of an airport there is an increased risk of bird strike. Flocks of birds crossing the runway corridor of the new runway Northwest of the Frankfurt airport are kept under surveillance now with in total three watch towers located at the river Main which in this case is the preferred used line of orientation. Each of the watch towers carries an early warning system which consists of two pairs of stereoscopic thermal imaging cameras sensitive in the mid wavelength infrared range (3 - 5 μm). A stereoscopic pair measures the swarm size, direction of flight and velocity in real time and with high accuracy. From these results an early warning is derived under all relevant weather conditions. The fixed focus thermal imaging cameras are thermally compensated and designed for ultra low image distortion. Each stereoscopic pair is aligned in the sub-pixel range and is controlled by a reference beam to ensure that the alignment is preserved under all environmental conditions and over a very long time. The technical concept is discussed and the design of the realized warning system at the Frankfurt airport is presented.

Long range object identi¯cation needs visual identi¯cation over large distances. However, atmospheric turbulence does hinder long range imaging. Therefore it is crucial to compensate the visual artifacts due to atmospheric turbulence. In this paper we propose a new method to compensate these turbulence e®ects, thus enabling identi¯cation at larger distances. Our method is based on applying phase diversity imaging by a wavefront modulator in free-running mode. As we have no feedback loop, we can simultaneously compensate turbulence for multiple isoplanatic angles. The wavefront modulator generates several images with known additional wave front aberrations. This extra information allows us to locally estimate the optimal wave front aberration and thus the optimal - turbulence free - image can be derived. This paper provides results on simulated data showing that this method performs well under realistic turbulence and noise conditions. Furthermore the robustness of the proposed method is shown for varying algorithmic settings.

Early vision stages represent a considerably heavy computational load. A huge amount of data needs to be processed under strict timing and power requirements. Conventional architectures usually fail to adhere to the specifications in many application fields, especially when autonomous vision-enabled devices are to be implemented, like in lightweight UAVs, robotics or wireless sensor networks. A bioinspired architectural approach can be employed consisting of a hierarchical division of the processing chain, conveying the highest computational demand to the focal plane. There, distributed processing elements, concurrent with the photosensitive devices, influence the image capture and generate a pre-processed representation of the scene where only the information of interest for subsequent stages remains. These focal-plane operators are implemented by analog building blocks, which may individually be a little imprecise, but as a whole render the appropriate image processing very efficiently. As a proof of concept, we have developed a 176x144-pixel smart CMOS imager that delivers lighter but enriched representations of the scene. Each pixel of the array contains a photosensor and some switches and weighted paths allowing reconfigurable resolution and spatial filtering. An energy-based image representation is also supported. These functionalities greatly simplify the operation of the subsequent digital processor implementing the high level logic of the vision algorithm. The resulting figures, 5.6mW@30fps, permit the integration of the smart image sensor with a wireless interface module (Imote2 from Memsic Corp.) for the development of vision-enabled WSN applications.

Modern electro-optical systems contain several components such as thermal imager, laser designator, laser range finder, etc. The demand for compact systems with low power consumption and low cost can be addressed by incorporating some of the traditional system abilities into the IR detector. We present SNIR, a new type of detector, which consists of a Read Out Integrated Circuit (ROIC) with advanced on-chip signal processing. The ROIC is flip chip-bonded to a 640x512 InSb detector array of 15μm pitch. SNIR digital ROIC can be operated in either one of the following four different modes of operation. The first operation mode is standard thermal imaging, which has typical functionalities and performance of MWIR detector. The second operation mode is a dual-function mode that includes both standard thermal imaging and information on Asynchronous Laser Pulse Detection (ALPD) for each pixel. The detection probability of a laser pulse is significantly increased by integrating a dedicated in-pixel circuit for identifying a fast signal temporal profile. Since each pixel has internal processing to identify laser pulses, it is possible also to measure the elapsed time between a trigger and the detection of a laser pulse. This yields a third mode of operation in which the detector is synchronized to a laser and becomes a Two-dimensional Laser Range Finder (TLRF). The forth operation mode is dedicated to Low Noise Imaging (LNIM) for the SWIR band, where the IR radiation signal is low. It can be used in both passive or active imaging. We review some of the predicted and measured results for the different modes of operation, both at the detector level and at the system level.

This paper describes an approach for accurately simulating the reset noise of CTIA-based pixels. Using a circuit simulator to find the reset noise of a CTIA based pixel is not straightforward, due to the noise sampling and charge redistribution after the reset switch opens. This often leads to an equation-based analysis of the pixel noise, which is cumbersome for actual design work and incompatible with a mixed-signal design flow for advanced ROIC designs. In a CTIA-based ROIC, the start of pixel integration is defined by the opening of the CTIA reset switch. The opening of this switch down-converts the wideband noise of the circuit to DC, and the charge is then redistributed by the CTIA to create an output reset noise. This reset noise can be removed by correlated double sampling (CDS). However, it is important to understand the magnitude of the reset noise in order to evaluate the effectiveness of the CDS scheme. CDS can be performed either in the pixel, or externally in the analog or digital domains. The specifications of the signal chain depend on the amount of reset noise and the degree of cancellation required. Simulation of the reset noise in SPICE is not straightforward, since the charge is redistributed after the switch opens, and the noise on the two capacitors is correlated and cannot be treated independently. We describe a simulation technique that gives accurate estimates of the pixel reset noise, and verify the results using Spectre-RF.

Advances in nanofabrication allow for the creation of metallic nanowires acting as linear polarizers in the visible and near infrared regime. The monolithic integration of silicon detectors and pixelated nanowire metallic polarization filters allows for an efficient realization of high resolution polarization imaging sensors. These silicon sensors, known as division of focal plane polarimeters, capture polarization information of the imaged environment from ~400nm to 1050nm wavelength. The performance of the polarization sensor can be degraded by both irregularities in the fabrication of the nanowires and possible misalignment errors during the final deposition of the optical nanowire filters on the surface of the imaging sensor. In addition, electronic offsets due to the readout circuitry, electronic crosstalk, and optical crosstalk will also negatively affect the quality of the polarization information. Partial compensation for many of these post-fabrication errors can be accomplished through the use of a camera calibration routine. This paper will describe one such routine, and show how its application can increase the quality of measurements in both the degree of linear polarization and angle of polarization in the visible spectrum. The imaging array of the division of focal plane polarimeter is segmented into two by two blocks of superpixels. The calibration method chooses one of the four pixels as a reference, and then a gain and offset for each of the remaining three is computed based on this reference. The output is a calibration matrix for each pixel in the image array.

It has been known since the early 1960s that hexagonal sampling is the optimal sampling approach for isotropically band-limited images, providing a 13.4% improvement in sampling efficiency over rectangular sampling. Despite this fact and other significant advantages of hexagonal sampling, rectangular sampling is still used for virtually all modern digital image processing systems. This is arguably due to the lack of an efficient addressing system for hexagonal grids. Array set addressing (ASA) is a recent advance in addressing hexagonal grids that allows image processing techniques to be performed efficiently on hexagonally sampled images. This paper will describe ASA and discuss its advantages. With ASA, a renewed interest in sensors that sample hexagonally is occurring. We will describe a new visible imager that simultaneously samples both hexagonally and rectangularly. This novel research tool has the ability to provide real imagery that can be used to quantitatively compare the performance of an image processing operation on both hexagonally sampled and rectangularly sampled images. We will also describe current efforts and plans for future visible sensors that sample hexagonally. The advantages of hexagonal sampling are not limited to the visible domain and should be equally realizable in the infrared domain. This paper will discuss considerations for developing infrared sensors that sample hexagonally. On-focal plane array (FPA) processing, readout architectures, detector materials, and bump-bonding are among the topics to be discussed.

A high-fill factor/high-SNR CMOS readout integrated circuit (ROIC) array is designed for high dynamic range infrared imaging systems. The designed ROIC array uses a single reference photodiode that is routed to each unit cell in the array to subtract the dark current for high SNR and high fill factor. The achieved average SNR is 80 dB and the fill factor is 28% with a 25 x 25 μm² unit cell size. With this new unit cell and routing approach, the size of the unit cell is reduced by 300% compared to other high SNR circuits. The maximum power consumption per unit pixel is 500nW.

In this paper, we propose multiple demeaning filters for small target detection in infrared (IR) images. The use of a demeaning filter is a promising method which detects a small object by removing the background components with a mean filter. The main factors in the design of a demeaning filter are two types of demeaning methods and the size of its window. We compare two demeaning methods, the sliding window method and the grid method, and we analyze the trade-off between the window size and the performance of the demeaning filters and present limitations related to their use. To overcome the drawbacks of a conventional demeaning filter, the use of multiple demeaning filters with filters of various sizes is considered. The proposed method not only has the advantage of being able to detect a small object in a densely cluttered environment, but it also can be used with low complexity with an integral image. Experimental results demonstrate the robustness and stability of the proposed multiple demeaning filters with low computational complexity compared with conventional methods.

Infrared cameras are used in various military applications for early detection and observation. In applications where very fast image acquisition is needed the so called cooled detectors are used. Cooled detectors are a kind of detectors that demands cryogenic cooling, but in return provide exceptional performance and temperature sensitivity with low integration times. These features predestinate cooled detectors for special purposes like airborne systems, where fast and precise infrared radiation measurement is needed. Modern infrared cooled detector arrays like HgCdTe Epsilon detector from Sofradir with spectral range of 3.5μm-5μm can provide high frame rate reaching 140Hz with full frame readout. Increasing frame rates of cooled infrared detectors demands fast and efficient image processing modules for necessary operations like nonuniformity correction, bad pixel replacement and visualization. For that kind of detector array a fast image processing module was developed. The module is made of two separate FPGA modules and configuration processor. One FPGA was responsible for infrared data processing, and was performing nonuniformity correction, bad pixel replacement, linear and nonlinear filtering in spatial domain and dynamic range compression. Second FPGA was responsible for interfacing infrared data stream to standard video interfaces. It was responsible for frame rate conversion, image scaling and interpolation, and controlling ASICs for video interface realization. Both FPGAs use several external resources like SRAM and DRAM memories. The input interface was developed to connect with Epsilink board which is a standard proximity board provided by Sofradir for this kind of detector. The image processing chain is capable of performing real-time processing on data stream of volume up to about 40 Megapixels per second.

Design and measurement of a silicon readout integrated circuit (ROIC) based on switched capacitor time delay integration (TDI) technique for LWIR HgCdTe Focal Plane is presented. ROIC incorporates time delay integration (TDI) functionality for scanning type of detector by using switched capacitor technique with a supersampling rate of three, increasing SNR and the spatial resolution. ROIC, in terms of functionality, is capable of bidirectional scan, programmable integration time, 5 gain settings at the input and auto gain adjustment with pixel deselection capability. Programming can be done parallel or serially with test mode functionality. ROIC can handle up to 3.75V dynamic range with the load being 25pF capacitive, output settling time is less than 80 nsec. This low power ROIC consumes less than 100mW. Moreover, input referred noise is less than 750 rms electrons. Simulations and measurements are done in both room temperature and cryogenic (77 °K) temperatures. In order to measure and simulate chip without a detector, process and temperature invariant current source block that imitate detector currents are designed as well. The manufacturing technology is 0.35μm, double poly-Si, four-metal (3 metals and 1 top metal) 5V CMOS process.

This paper presents different imaging interpolation methods implemented for the division of focal plane polarization imaging sensor. The targeted polarization imaging sensor is a CCD based sensor with 1-Mega pixels resolution operating from 400nm to 1050nm wavelength. The five interpolation methods considered in this paper are: bilinear, weighted bilinear, bicubic spline, an approximated bicubic spline and a bicubic interpolation method. Test images of the five different interpolation methods as well as numerical error analysis are presented. Based on the comparison results, the full frame bicubic spline interpolation achieves the best performance for polarization images.

We report a longwave infrared quantum dot infrared photodetector working at room temperature (RT) (298K). A photoresponsivity and photodetectivity of 0.02A/W and 9.0x10⁶ cmHz^1/2/W was achieved at 298K with a low bias voltage of -0.1V. The RT QDIP avoids bulk and heavy cryogenic cooling systems and thus enables the development of ultra-compact IR sensing and imaging systems.

One of the key features of quantum well infrared photodetectors is the narrow absorption band. However, some applications, as the infrared spectroscopy, require broadband detection. Several approaches have been used to get a broadband response with QWIPs (superlattices, digital graded barriers, stacks, etc.). In this paper, we focus on the interlaced configuration and on the coupled wells structure. Both designs exhibit broadband response covering the [11-15 μm] spectral range. The experimental dependencies of the spectral shape versus the temperature and bias voltage are discussed. Based on numerical model, we propose a specific design strategy which leads to a spectral shape quasiindependent on the operating conditions.

The focal plane assembly for the Thermal Infrared Sensor (TIRS) instrument on NASA's Landsat Data Continuity Mission (LDCM) consists of three 512 x 640 GaAs Quantum Well Infrared Photodetector (QWIP) arrays. The three arrays are precisely mounted and aligned on a silicon carrier substrate to provide a continuous viewing swath of 1850 pixels in two spectral bands defined by filters placed in close proximity to the detector surfaces. The QWIP arrays are hybridized to Indigo ISC9803 readout integrated circuits (ROICs). QWIP arrays were evaluated from four laboratories; QmagiQ, (Nashua, NH), Army Research Laboratory, (Adelphi, MD), NASA/ Goddard Space Flight Center, (Greenbelt, MD) and Thales, (Palaiseau, France). All were found to be suitable. The final discriminating parameter was the spectral uniformity of individual pixels relative to each other. The performance of the QWIP arrays and the fully assembled, NASA flight-qualified, focal plane assembly will be reviewed. An overview of the focal plane assembly including the construction and test requirements of the focal plane will also be described.

Rigorous electromagnetic (EM) field modeling is applied to calculate the external quantum efficiency (QE) of various quantum well infrared photodetector (QWIP) pixel geometries with thinned substrates. We found that for a 24 × 24 × 1.5 μm³ cross-grating QWIP, the QE is peaked at 13.0, 11.0, and 8.4 μm, insensitive to the grating periods. These peaks are identified as the first three harmonic resonances associated with the pixel resonant cavity. For a regular prismshaped corrugated QWIP (C-QWIPs) with a 25-μm pitch, the QE oscillates about its classical value of 24.5% within the calculated wavelength range from 3 to 15 μm. A peaked value of 32% occurs at 9.1 μm. For pyramidal C-QWIPs, the maximum QE is 42%, and for cone-shaped C-QWIPs, it is 35%. In the presence of an anti-reflection coating, the oscillation amplitude diminishes, and the average values generally rise to near the peaks of the oscillations. The modeling results are compared with the experimental data for grating QWIP focal plane arrays (FPAs) and prismshaped C-QWIP FPAs; satisfactory agreements were achieved for both. After verifying our EM approach, we explored other detector geometries and found new types of resonator QWIPs (R-QWIPs) that can provide 30% QE at certain wavelengths on a 1.5-μm-thick active material. Combining the high QE of a resonator and the high gain of a thin material layer, the new R-QWIPs will have a conversion efficiency far higher than the existing QWIP detectors. The present resonator approach will also have an impact on other detector technologies.

Much progress has been made in the past 2 years in developing III-V antimonide-based superlattice infrared detectors and focal plane arrays (FPAs). In the area of detector material growth by molecular beam epitaxy, the wafer foundry group, helped by government-trusted entities and other partnering institutions, has leapfrogged many years of R&D effort to become the premier detector wafer supplier. The wafers produced are of high quality as measured by surface morphology, defect density, photoluminescence property, high-resolution X-ray diffraction, and diode current-voltage characteristics. In the area of detector design and FPA processing, the team-consisting of members from government laboratories, academia, and the FPA industry-has made rapid progress in device structure design, detector array etching, passivation, hybridization, and packaging. The progress is reflected in the steady reduction in FPA median darkcurrent density and improvement in median quantum efficiency, as well as reasonably low median noise-equivalent different temperature under 300 K scene background, when compared with the performance from some of the commercially available HgCdTe FPAs. In parallel with the FPA research and development effort, a small amount of funding has been devoted to measuring minority carrier lifetimes and to understanding life-killing defects and mechanisms of superlattice devices. Results of direct time-resolved photoluminescence measurement on superlattice absorbers indicate relatively short lifetimes (on the order of 30 ns) due to Shockley-Read-Hall mechanism. Modeling and curve fitting with diode current-voltage data indicate longer minority carrier lifetimes, although the best fit lifetime values differ greatly, possibly due to the difference in material quality and device structure. Several models or hypotheses have been proposed to explain experimental data. More data are required to validate these models and hypotheses. Further work is also necessary to reconcile the substantially different results from different groups and to truly understand the physics of minority carrier lifetimes, which is necessary to improve the lifetime and realize the theoretical promise of superlattice materials.

Infrared detection technologies entering the third generation demand performances for higher detectivity, higher operating temperature, higher resolution and multi-color detection, all accomplished with better yield and lower manufacturing/operating costs. Type-II antimonide based superlattices (T2SL) are making firm steps toward the new era of focal plane array imaging as witnessed in the unique advantages and significant progress achieved in recent years. In this talk, we will present the four research themes towards third generation imagers based on T2SL at the Center for Quantum Devices. High performance LWIR megapixel focal plane arrays (FPAs) are demonstrated at 80K with an NEDT of 23.6mK using f/2 optics, an integration time of 0.13ms and a 300K background. MWIR and LWIR FPAs on non-native GaAs substrates are demonstrated as a proof of concept for the cost reduction and mass production of this technology. In the MWIR regime, progress has been made to elevate the operating temperature of the device, in order to avoid the burden of liquid nitrogen cooling. We have demonstrated a quantum efficiency above 50%, and a specific detectivity of 1.05x10¹² cm.Hz^1/2/W at 150K for 4.2μm cut-off single element devices. Progress on LWIR/LWIR dual color FPAs as well as novel approaches for FPA fabrication will also be discussed.

InAs/GaSb-based type-II superlattice photodiodes have considerably gained interest as high-performance infrared detectors. Beside the excellent properties of InAs/GaSb superlattices, like the relatively high effective electron mass suppressing tunneling currents, the low Auger recombination rate, and a high quantum efficiency, the bandgap can be widely adjusted within the infrared spectral range from 3 - 30 μm depending on the layer thickness rather than on composition. Superlattice growth and process technology have shown tremendous progress during the last years. Fully integrated superlattice cameras have been demonstrated by several groups worldwide. Within very few years, the InAs/GaSb superlattice technology has proven its suitability for high-performance infrared imaging detector arrays. At Fraunhofer IAF and AIM, the efforts have been focused on developing a mature fabrication technology for bispectral InAs/GaSb superlattice focal plane arrays for a simultaneous, co-located detection at 3-4 μm and 4-5 μm in the mid-wavelength infrared atmospheric transmission window. A very low number of pixel outages and cluster defects is mandatory for dual-color detector arrays. Sources for pixel outages are manifold and might be caused by dislocations in the substrate, the epitaxial growth process or by imperfections during the focal plane array fabrication process. Process refinements, intense root cause analysis and specific test methodologies employed at various stages during the process have proven to be the key for yield enhancements.

Relationship between V/III beam equivalent pressure (BEP) flux ratios during the molecular beam epitaxial (MBE) growth of long-wave infrared InAs/GaSb strained layer superlattice (SLS) material, crystalline quality of asgrown material, and devices' signal (responsivity) and noise (dark current) characteristics was investigated. It was found that the V/III ratio is a critical factor affecting the dark current, cut off wavelength and the responsivity of the device. Modest change of As/In BEP flux ratio (from 5.5 to 7) resulted in red-shift of cut-off wavelength by 0.6 μm. Temperature-dependent dark current measurements revealed more than two orders of magnitude difference in dark current densities of detectors grown with different As/In BEP flux ratios. The highest responsivity and QE values, equal to 0.75 A/W and 10% (74K, 9 μm, -0.4V), were demonstrated by the device with highest dark current density and notoptimal structural properties. The observed dependences of devices' signal (responsivity) and noise (dark current) characteristics in conjunction with the structural properties and the growth conditions of SLS material suggest that the good structural properties of grown detector material as well as low noise would not necessary result in improved device performance.

GaInSb and AlGaInSb compositionally graded buffer layers grown on GaSb by MBE were used to develop unrelaxed InAs_1-XSb_Xepilayers with lattice constants up to 2.1 % larger than that of GaSb. The InAsSb buffer layer was used to grow InAs_0.12Sb_0.88 layer on InSb. The structural and optical characterization of 1-μm thick InAs_1-xSb_x layers was performed together with measurements of the carrier lifetime.

We report on dual-band (mid-/long-wave infrared) InAs/GaSb strained layer superlattice detector with nBn and pBp architectures. Two band response was registered with 50% cut-off wavelengths of 5μm (both nBn and pBp detectors) and 9μm (nBn)/10μm (pBp). The maximum peak responsivity of MWIR absorber equal to 1.6 A/W (at λ = 5 μm and V_b = +1 V) and LWIR absorber equal to 1.2 A/W (at λ = 10 μm and V_b = -1 V) for nBn detector, with the corresponding values of D* were 1.2 x 10¹¹ Jones and 1.2 x 10¹⁰Jones for MWIR and LWIR absorbers, respectively (77 K). The maximum values of quantum efficiency were estimated to 36% (MWIR) and 15% (LWIR) at V_b = +1V and V_b = -1V. For pBp detector, the responsivity equal to 1.6 A/W (at λ = 5 μm and V_b = +0.4 V) and 1.8 A/W (at λ = 9 μm and V_b = -0.7 V) for MWIR and LWIR absorbers was achieved with corresponding values of specific detectivity 5 x 10¹¹ Jones and 2.6 x 10¹⁰Jones, respectively. The maximum values of quantum efficiency were estimated to 41% (MWIR) and 25% (LWIR) at V_b = +0.4V and V_b = -0.7V. Moreover, the diffusion-limited behavior of dark current at higher temperatures was observed for MWIR absorber for pBp detector. The overall performance of the dual-band InAs/GaSb SLS detectors with investigated designs showed comparable (nBn design) and superior (pBp design) performance to the QWIP detectors both in MWIR and LWIR bands and comparable performance to MCT detectors in MWIR band (nBn and pBp detector designs).

In this work, we report on the measurement of vertical transport parameters in p-doped InAs/GaSb type-II superlattices for long-wavelength infrared detectors. Variable magnetic eld geometrical magnetoresistance mea- surements have been employed to extract the vertical transport parameters, since the Hall-eect technique cannot be employed in the vertical transport conguration. The room-temperature magnetoresistance measurements were performed employing a kelvin-mode set up, at electric elds not exceeding 25 V/cm and at magnetic eld intensities up to 12 T. The measured magnetoresistance, shown to exhibit multiple-carrier conduction charac- teristics, were analyzed using a high-resolution mobility spectrum analysis technique. It is shown that, at room temperature, the electrical conductivity of the sample is due to four distinct carriers, associated with the major- ity carrier holes, sidewall inversion layer electrons, and two minority carrier electrons likely associated with two distinct conduction band levels.

We report the full electrooptical characterization of a MWIR InAs/GaSb superlattice (SL) pin photodiode, including dark current, noise, spectral response and quantum efficiency measurements. The SL structure was made of 8 InAs monolayers (MLs) and 8 GaSb MLs, with a total thickness of 3μm. It exhibits a cut-off wavelength of 4.55 μm at 77K. Dark current measurements reveal a diffusion-limited behavior for temperatures higher than 95K, and a R0A value of 1x10⁶Ωcm² at 77K. Noise measurements were performed under dark conditions and are interpreted in this paper. The results show that the SL detector remains Schottky noise-limited up to a bias voltage of -600mV and that 1/f noise is not present above 6Hz. Spectral response revealed that the cut-off wavelength increases from 4.48μm to 4.91μm when the temperature increases from 12K to 170K. The quantum efficiency in photovoltaic mode and at 77K is 25% (3μm-thick active zone device, single pass and without any antireflection coating). All these electrooptical performances confirm the high quality of the MWIR SL pin photodiode under test.

Recent experiments on conventional p-on-n and n-on-p Type II superlattices (SLS) infrared detectors still indicate larger than theoretically predicted dark current densities, despite the well known suppression of the Auger recombination mechanism. Rather, dark current in SLS is thought to still be limited by trap-assisted tunneling in the depletion region and surface leakage currents resulting from lack of fully passivated mesa sidewalls. An emerging infrared detector technology utilizing a unipolar, single-band barrier design, the so-called nBn architecture, potentially suppresses these remaining noise current mechanisms. In this report, measurements of the noise current spectral density of a mid-wave infrared nBn detector, composed of a type-II InAs/GaSb strain layer superlattice (SLS) absorber (n) and contact (n) layers with an AlGaSb barrier (B), under low-temperature, low-background conditions are presented. Here, noise was measured using a transimpedance amplifier incorporating a dewar-mounted feedback resistor R_F and source-follower MOSFET, both held at 77 K. This configuration confines high detector impedance issues to the dewar, minimizes Johnson noise due to the electronics, and enhances bandwidth by reducing stray capacitance. Features of the detector's noise spectrums at different bias are examined.

In this paper we describe the growth and characterization of antimonide based compound semiconductor substrates. The Czochralski technique has been used to grow single crystals of 4" InSb and 4" GaSb with dislocation densities of <20/cm² and <100/cm², respectively. Epitaxy ready wafer surfaces have been characterized by surface microscopy and spectroscopic ellipsometry, revealing sub-nanometer levels of surface roughness (rms) and oxide coverage in the 10-50 Angstrom range. GaSb wafers with thinner oxides (<20 Angstroms) have been developed and quality assessments made by epitaxial growth testing. Surface morphology evaluations indicate high levels of surface quality, comparable to pretreated variants of the same substrate type. We also illustrate current crystal growth systems and ingot forms, and discuss the challenges associated with scaling present InSb and GaSb technologies to deliver larger substrate formats.

Recent efforts in developing InAs/GaSb strained-layer superlattices for LWIR detectors are described. The structural properties of the devices grown by MBE at HRL were evaluated using optical microscopy, x-ray diffraction, and atomic force microscopy. Epilayer roughness and surface morphology are briefly described. Small format focal plane arrays were fabricated to serve as a baseline for device study, and to determine the effects of underfill epoxy on detector performance. A novel approach for epilayer transfer on silicon is also presented.

Symmetric and asymmetric mid-wavelength infrared (MWIR) InAs/GaSb superlattice (SL) pin photodiode were fabricated by Molecular Beam Epitaxy (MBE) on p-type GaSb substrate and characterized as a function of temperature. The symmetric SL structure was made of 8 InAs monolayers (MLs) and 8 GaSb MLs and exhibits at 80K a cut-off wavelength (λc) of 4.5μm, while the asymmetric SL design was composed of 7.5 InAs MLs and 3.5 GaSb MLs for λc = 5.5μm at 80K. Optical characterizations made of photoluminescence as a function of temperature and room temperature absorption spectra were performed on these two kinds of structures. Several electrical characterizations including dark current and capacitance-voltage measurements were also carried out on single detectors in the temperature range [77K-300K]. Results obtained were compared and analyzed in order to define optimized SL structure design for the high performance in the MWIR domain.

We report recent efforts in achieving state-of-the-art performance in type-II superlattice based infrared photodetectors using the barrier infrared detector architecture. We used photoluminescence measurements for evaluating detector material and studied the influence of the material quality on the intensity of the photoluminescence. We performed direct noise measurements of the superlattice detectors and demonstrated that while intrinsic 1/f noise is absent in superlattice heterodiode, side-wall leakage current can become a source of strong frequency-dependent noise. We developed an effective dry etching process for these complex antimonide-based superlattices that enabled us to fabricate single pixel devices as well as large format focal plane arrays. We describe the demonstration of a 1024×1024 pixel long-wavelength infrared focal plane array based the complementary barrier infrared detector (CBIRD) design. An 11.5 μm cutoff focal plane without anti-reflection coating has yielded noise equivalent differential temperature of 53 mK at operating temperature of 80 K, with 300 K background and cold-stop. Imaging results from a recent 10 μm cutoff focal plane array are also presented.

A key component for third generation FPA development is the megapixel strain layer superlattice (SLS) structures on GaSb substrates for advanced infrared detectors. A significant aspect that inhibits widespread application of large format device growth on GaSb is the starting substrate size. Recently, the Czochralski method resulted in the world's first 100mm GaSb boules. The 100mm GaSb substrates can be ultra-low doped (n~4-9x10¹⁵/cm³) for extended IR wavelength transparency. A plethora of changes to the manufacturing process is required for consistent 100mm GaSb growth and substrate polishing. In this study, we examined the surface quality of the 100mm GaSb as a function of a standard and experimental Polish "A" which incorporated an additional CMP step as well as a longer final polish time. Atomic force microscopy (AFM) and power spectral density (PSD) as a function of polish process measured the surface morphology. Interferometry was used to analyze free standing wafer flatness. Electron spectroscopy for chemical analysis (ESCA) determined surface oxide thickness, and successful MBE growth of a 400 period Complimentary Barrier Infrared Detector (CBIRD) structure assessed SLS based device suitability. The epi structure was examined by x-ray diffraction (XRD). The low 0.3-0.4nm Ra starting 100mm GaSb roughness values, the wafer flatness ~2.3μm per 16 wafer batch, the low FWHM SLo = 15.48 arsec of the successful CBIRD epi growth and related high intensity XRD ~6.6nm periodicity peaks suggest that the modified polish provides the 100mm GaSb with a desirable epi ready character and excellent surface crystallinity for advanced IRFPA applications.

Most of today's commercial solutions for un-cooled IR imaging sensors are based on resistive bolometers using either Vanadium oxide (VOx) or amorphous Silicon (a-Si) as the thermistor material. Despite the long history for both concepts, market penetration outside high-end applications is still limited. By allowing actors in adjacent fields, such as those from the MEMS industry, to enter the market, this situation could change. This requires, however, that technologies fitting their tools and processes are developed. Heterogeneous integration of Si/SiGe quantum well bolometers on standard CMOS read out circuits is one approach that could easily be adopted by the MEMS industry. Due to its mono crystalline nature, the Si/SiGe thermistor material has excellent noise properties that result in a state-ofthe- art signal-to-noise ratio. The material is also stable at temperatures well above 450°C which offers great flexibility for both sensor integration and novel vacuum packaging concepts. We have previously reported on heterogeneous integration of Si/SiGe quantum well bolometers with pitches of 40μm x 40μm and 25μm x 25μm. The technology scales well to smaller pixel pitches and in this paper, we will report on our work on developing heterogeneous integration for Si/SiGe QW bolometers with a pixel pitch of 17μm x 17μm.

Metal-oxide-metal (MOM) tunnel diode detectors when integrated with phased-array antennas provide determination of the angle of arrival and degree of coherence of received infrared radiation. Angle-of-arrival measurements are made with a pair of dipole antennas coupled to a MOM diode through a coplanar strip transmission line. The direction of maximum angular response is altered by varying the position of the MOM diode along the transmission line connecting the antenna elements. Phased-array antennas can also be used to measure the degree of coherence of a partially coherent infrared field. With a two-element array, the degree of coherence is a measure of the correlation of electric fields received by the antennas as a function of the element separation. Antenna-coupled MOM diode devices are fabricated using electron beam lithography and thin-film deposition through a resist shadow mask. Measurements at 10.6 μm are substantiated by electromagnetic simulations and compared to analytic results.

Hostile fire indication (HFI) systems require high-resolution sensor operation at extremely high speeds to capture hostile fire events, including rocket-propelled grenades, anti-aircraft artillery, heavy machine guns, anti-tank guided missiles and small arms. HFI must also be conducted in a waveband with large available signal and low background clutter, in particular the mid-wavelength infrared (MWIR). The shortcoming of current HFI sensors in the MWIR is the bandwidth of the sensor is not sufficient to achieve the required frame rate at the high sensor resolution. Furthermore, current HFI sensors require cryogenic cooling that contributes to size, weight, and power (SWAP) in aircraft-mounted applications where these factors are at a premium. Based on its uncooled photomechanical infrared imaging technology, Agiltron has developed a low-SWAP, high-speed MWIR HFI sensor that breaks the bandwidth bottleneck typical of current infrared sensors. This accomplishment is made possible by using a commercial-off-the-shelf, high-performance visible imager as the readout integrated circuit and physically separating this visible imager from the MWIR-optimized photomechanical sensor chip. With this approach, we have achieved high-resolution operation of our MWIR HFI sensor at 1000 fps, which is unprecedented for an uncooled infrared sensor. We have field tested our MWIR HFI sensor for detecting all hostile fire events mentioned above at several test ranges under a wide range of environmental conditions. The field testing results will be presented.

At the 2010 meeting of the Defense and Security Symposia Raytheon reported on the status of their efforts to establish a high rate uncooled detector manufacturing capability. At that time we had just finished the transition of the 640 × 480, 25 μm product to our 200 mm wafer fab line at Freescale semiconductor and established an automated packaging and test capability. Over the past year we have continued to build on that foundation. In this paper we will report on this year's progress in completing the transition of our 25 μm product line to Freescale semiconductor. Included will be the 320 × 240 product transition and a summary of SPC and defectivity data from one year's production. Looking beyond 25 μm, we are well along in our transition of the 17 μm product line to Freescale, with test results being available for the 640 × 480. Additionally, we will report on progress / status of the Tailwind program, which is developing a 2048 × 1536, 17 μm uncooled sensor. Data to be reported includes the establishment of subfield stitching at a high rate commercial fab and the development of the detector package and electronics. With 17 μm transitioned to production, Raytheon has started work on the HD LWIR program, which is laying the foundation for the next generation of uncooled detectors by further shrinking the pixel to <17 μm. With the HD LWIR program just beginning, we will review our development strategy and program plan.

Uncooled Terahertz (THz) focal plane array (FPA), 320x240 format-23.5 μm pitch, and THz imager were developed. There are two types of THz-FPAs, i.e., broad-band type and narrow-band type. Since broad-band type THz-FPA was developed, a couple of modifications have been made to improve Noise Equivalent Power. The narrow-band type THz-FPA has such a new structure that Si cover is put above thermal isolation structure of broad-band type THz-FPA at a distance of half of wavelength of interest. Measurements on responsivities of narrow-band type FPAs show enhancement by a factor of ca. 3. Lock-in imaging technique has been developed, which increases signal-to-noise ratio as a function of square root of the number of frames of integration. Both passive and active THz imaging experiments were finally described.

The high level of accumulated expertise by ULIS and CEA/LETI on uncooled microbolometers made from amorphous silicon has enabled ULIS to develop VGA IRFPA formats with 17 μm pixel-pitch, hence building up the currently available product catalog. This detector keeps all the innovations developed on the 25 μm pixel-pitch ROIC (detector configuration by serial link, low power consumption and wide electrical dynamic range). The specific appeal of this unit lies in the high spatial resolution it provides. The pixel-pitch reduction turns this TEC-less VGA array into a product well adapted for high resolution and compact systems. Electro-optical performances of this IRFPA are presented hereafter as well as recent performance improvement. We will focus on NETD trade-off with wide thermal dynamic range, as well as the high characteristics uniformity and pixel operability, achieved thanks to the mastering of amorphous silicon technology coupled with the ROIC design. Solar exposure is also taken into account and shows that ULIS amorphous silicon is perfectly well suited to sustain high intensity exposure. This technology node associated with advanced packaging technique paves the way to compact low power system.

The market demand for low SWaP (Size, Weight and Power) uncooled engines keeps growing. Low SWaP is especially critical in battery-operated applications such as goggles and Thermal Weapon Sights. A new approach for the design of the engines was implemented by SCD to optimize size and power consumption at system level. The new approach described in the paper, consists of: 1. A modular hardware design that allows the user to define the exact level of integration needed for his system 2. An "open architecture" based on the OMAP^TM530 DSP that allows the integrator to take advantage of unused hardware (FPGA) and software (DSP) resources, for implementation of additional algorithms or functionality. The approach was successfully implemented on the first generation of 25μm pitch BIRD detectors, and more recently on the new, 640 x480, 17 μm pitch detector.

Scalable new SOI diode structure has been proposed and developed for beyond 17μm pixel pitch mega-pixel-class SOI diode uncooled infrared focal plane arrays (IRFPAs). Conventionally, each p⁺n vertical diode is formed between a p⁺diffusion and an n-body in each SOI active area, and 8-10 diodes are serially connected with interconnections. In the proposed new structure, we employ two kinds of diodes, namely, p⁺n and n⁺p vertical diodes. First, two regions of an nbody and a p-body are prepared in an SOI active area. In the n-body, a p⁺ diffusion is formed apart from the n-body /pbody boundary. In the p-body, an n+ diffusion is formed apart from the boundary. In this way, a p⁺n vertical diode and an n+p vertical diode are formed together in an SOI active area. Moreover, a contact hole, which is formed in touch with both n- and p-bodies, electrically connects these two kinds of diodes. With this new structure which is named "new 2-in- 1 SOI diode structure", we have realized remarkable reduction of the diode area. It leads to significant increase of the diode series number in a pixel, which increases infrared responsivity of the pixel. As a result, designing a 15μm pixel pitch IRFPA with the new structure, 12 series diodes can be arranged in a pixel, although 10 series diodes have been used even in the case of our 25μm pitch generation pixel. To confirm the ability of the new diodes, test elements of 12-17μm pitch pixels were fabricated and evaluated. Furthermore, the fabrication of 17μm pixel pitch 320 x 240 IRFPAs with the new diodes was carried out and their favorable FPA operations were successfully verified. In conclusion, the proposed and developed new SOI diode technology is very promising for beyond 17μm pixel pitch mega-pixel-class uncooled IRFPAs.

This paper presents the improvements of an advanced digital VGA-IRFPA developed by Fraunhofer-IMS. The uncooled IRFPA is designed for thermal imaging applications in the LWIR (8 .. 14 μm) range with a full-frame frequency of 30 Hz and a high sensitivity with NETD < 100 mK @ f/1. The microbolometer with a pixel-pitch of 25 μm consists of amorphous silicon as the sensing layer. The structure of the microbolometer has been optimized for a better performance compared to the 1st generation IRFPA1. The thermal isolation has been doubled by increasing the length and by decreasing the width of the legs. To increase the fill-factor the contact areas have been reduced. The microbolometers are read out by a novel readout architecture which utilizes massively parallel on-chip Sigma-Delta-ADCs. This results in a direct digital conversion of the resistance change of the microbolometer induced by incident infrared radiation. Two different solutions for the vacuum package have been developed. To reduce production costs a chip-scale-package is used. This vacuum package consists of an IR-transparent window with antireflection coating and a soldering frame which is fixed by a wafer-to-chip process directly on top of the read substrate. An alternative solution based on the use of a standard ceramic package is utilized as a vacuum package. This packaging solution is used for high performance applications. The IRFPAs are completely fabricated at Fraunhofer-IMS on 8" CMOS wafers with an additional surface micromachining process.

We have developed an uncooled infrared radiation focal plane array (IR-FPA) with 22 μm pitch and 320 × 240 pixels utilizing silicon p-n junction diodes, which were fabricated by 0.13 μm CMOS technology and bulk-micromachining. The thermal time response of cells was lowered to be 16msec by reduction of thermal capacity of cells. In addition to increase the sensitivity of cells by extending the length of supporting beams, p-n junction diode was scaled down as small as 20% in area compared to previous one. Micro-holes were formed in the cell to reduce only thermal capacity, which were negligibly small compared to incident IR wavelength. This method needs no additional process step and is considered as suitable for low cost and mass-productive IR-FPA.

An uncooled XGA camera core has been developed for multiple thermal imaging applications that require longer detection range and wider fields of view. The design challenge is to maintain high performance while optimizing for size, weight, and power (SWAP). Utilizing a combination of low power electronic designs, proprietary calibration methods, and a new 17μm pitch high performance amorphous silicon (ASi) microbolometer, a rugged multi-purpose SWAP-optimized XGA camera core has been designed. The result is a camera core that has been shown to deliver far better detection range and angle-of-view performance than previous uncooled solutions with frame rates of 30 Hz in XGA mode and 60 Hz in VGA mode.

As packaging represents a significant part of uncooled IR detectors price, a collective packaging process would contribute to enlarge uncooled IRFPA application to very low cost camera market. Since the first proof of the pixel level packaging for uncooled IRFPA in 2008, CEA-LETI is still strongly involved in the development of an innovative packaging technology. This one aims at encapsulating each pixel under vacuum in the direct continuity of the bolometer process. Moreover, a thin film getter has been developed to be integrated in the micropackaging so as to increase the packaging lifespan. This paper presents the recent development at CEA-LETI of this pixel level packaging technology including getter integration and vacuum level measurements.

Uncooled Infrared (IR) focal plane arrays are an enabling technology for both military and commercial high sensitivity night vision cameras. IR imaging is accomplished using MEMS microbolometers fabricated on read-out integrated circuits and depends critically on the material used to absorb the incoming IR radiation. Suitable detector materials must exhibit a large temperature coefficient of resistance (TCR) and low noise characteristics to efficiently detect IR photons while also maintaining compatibility with standard integrated circuit (IC) processing. The most commonly used material in uncooled infrared imaging detectors is vanadium oxide deposited by reactive ion beam sputtering. Here we present a comparison of vanadium oxide thin films grown via commercial reactive ion beam sputtering to films grown using reactive pulsed DC magnetron sputtering. Films deposited using both methods were optically and structurally characterized using Raman spectroscopy, transmission electron microscopy, atomic force microscopy and grazing incidence X-ray diffraction. The measured electrical properties of the films were found to be very sensitive to the deposition conditions used. The ion beam sputtered films contained twinned FCC VO_x nanocrystals with sub-nanometer twin spacing, in the form of large 10-20 nm wide columnar/conical grains. In contrast, the un-biased magnetron sputtered films consisted of equiax grains of FCC VO_x (5-10 nm) encapsulated in an amorphous matrix. However, applying an RF bias to the sample substrate during the magnetron sputtering process, resulted in films that are similar in structure to ion beam deposited VO_x. These differences in microstructure and composition were then correlated to the measured resistivities and TCRs of the films.

Uncooled amorphous silicon microbolometers have been established as a field-worthy technology for a broad range of applications where performance and form factor are paramount, such as soldier-borne systems. Recent developments in both bolometer materials and pixel design at L-3 in the 17μm pixel node have further advanced the state-of-the-art. Increasing the a-Si material temperature coefficient of resistance (TCR) has the impact of improving NETD sensitivity without increasing thermal time constant (TTC), leading to an improvement in the NETD×TTC product. By tuning the amorphous silicon thin-film microstructure using hydrogen dilution during deposition, films with high TCR have been developed. The electrical properties of these films have been shown to be stable even after thermal cycling to temperatures greater than 300^oC enabling wafer-level vacuum packaging currently performed at L-3 to reduce the size and weight of the vacuum packaged unit. Through appropriate selection of conditions during deposition, amorphous silicon of ~3.4% TCR has been integrated into the L-3 microbolometer manufacturing flow. By combining pixel design enhancements with improvements to amorphous silicon thin-film technology, L-3's amorphous silicon microbolometer technology will continue to provide the performance required to meet the needs to tomorrow's war-fighter.

Since authors have successfully demonstrated uncooled infrared (IR) focal plane array (FPA) with 23.5 um pixel pitch, it has been widely utilized for commercial applications such as thermography, security camera and so on. One of the key issues for uncooled IR detector technology is to shrink the pixel size. The smaller the pixel pitch, the more the IR camera products become compact and the less cost. This paper proposes a new pixel structure with a diaphragm and beams which are placed in different level, to realize an uncooled IRFPA with smaller pixel pitch )≤17 μm). The upper level consists of diaphragm with VOx bolometer and IR absorber layers, while the lower level consists of the two beams, which are designed to place on the adjacent pixels. The test devices of this pixel design with 12 um, 15 um and 17 um pitch have been fabricated on the Si ROIC of QVGA (320 × 240) with 23.5 um pitch. Their performances reveal nearly equal to the IRFPA with 23.5 um pitch. For example, noise equivalent temperature difference (NETD) of 12 μm pixel is 63.1 mK with thermal time constant of 14.5 msec. In addition, this new structure is expected to be more effective for the existing IRFPA with 23.5 um pitch in order to improve the IR responsivity.

This paper provides an overview of the recent DRS RSTA, Inc. (DRS) Vanadium Oxide (VOx) uncooled focal plane arrays (UFPA), sensor electronics, and camera development activities. Presently, DRS UFPAs consist of 25 μm and 17 μm pixel pitch detectors in 320x240 and 640x480 formats. Under the Army NVESD sponsored 17 μm Large Format Uncooled FPA Development program and internal projects, DRS has developed a 17 μm pitch 1024x768 UFPA product (U8000). The 17 μm pixel pitch UFPAs provide sensor systems with significant size, weight, and power (SWaP) savings as well as cost reductions over the 25 μm pixel pitch counterparts. There is a growing demand to transition current products to the 17 μm pixel technologies. For example, next generation military systems such as thermal weapon sights (TWS), enhanced night vision goggles (ENVG), driver viewer enhancers (DVE) and unmanned aerial vehicle (UAV) infrared (IR) surveillance sensors all called for the 17 μm pixel technologies. To meet market demand, DRS has improved its production facilities to accommodate 17 μm pixel detector manufacturing. In conjunction with these efforts, DRS has also developed a family of signal processing electronics based on a new FPGA architecture for various sensor modules and cameras that can be incorporated into commercial OEM products as well as DoD weapon systems. Under the DARPA funded AWARE Multiband (formerly DUDE) program, DRS and Goodrich Sensors Unlimited, Inc are collaborating on the development of a single, integrated, twocolor detector by combining the VOx microbolometer (8-14 μm) and InGaAs (0.4 -1.6 μm) detectors into a single focal plane array. The first AWARE Multiband dual mode focal plane array fabrication is now underway.

During microbolometer operation, the detector occasionally views high temperature scenes such as the sun or flames at very close distance. The detector temperature can then increase to a level so high that the sensing material experiences an annealing effect. Accordingly, the microbolometer is required to stand high temperatures that can cause device damage. In this paper, a bimorph leg integrated microbolometer structure is proposed. The bimorph leg is an extra leg that is separated from the signal transfer legs. It is bent downward and snaps onto the substrate when the microbolometer's temperature reaches a critical temperature. The temperature of the micro-bolometer is then decreased as heat is transferred to the substrate. By snapping the bimorph leg down onto the substrate, the microbolometer's thermal conductance is temporarily increased roughly three-fold higher than that of the normal state and thermal damage to the bolometer material can be effectively prevented. The increase of thermal conductance can be controlled by changing the size of the bimorph leg.

In this report, we describe the two different nickel oxide film formation processes for microbolometer application: the heat treatment of nickel metal and the reactive sputtering. Nickel oxide films obtained by the heat treatment of nickel show high TCR(about -3.2/°C) and low 1/f noise characteristic. The reactively sputtered nickel oxide films have the wide range of resistivity according to the sputtering vacuum level, time, and O₂/Ar gas partial pressure. The acquired TCR of sputtered films are in the range of -1.4%/°C and -3.45%°C. And the 1/f noise parameter k, which shows the performance between VOx and a-Si, is as low as 8.5×10^-13 at the TCR of -1.75%/°C. Acquired nickel oxide films were analyzed from XRD, AFM methods, and etc. It is regarded that the resistivity variation of polycrystalline nickel oxide film comes from nonstoichiometric property of nickel and oxygen atoms. We simulated the optic and membrane structure for predicting the performance of a microbolometer with nickel oxide film. The estimated NETD(noise equivalent temperature difference) for the 50μmx50μm size of pixel is NETD below 20mK.

In 2007 the compatibility of VPD PbSe and Silicon CMOS technologies was demonstrated. At that time, the first monolithic device, a laboratory demonstrator with 16x16 elements, was processed successfully. Since then the technology has evolved towards its industrial maturity and a number of new devices based on this material have been developed. Their performances have converted the VPD PbSe in one of the most promising technologies in the market for fast and low cost IR imagers. In this paper a brief historical review and the state of the art of the PbSe technology are presented, as well as the ultimate performances commercially available,the latest experimental results obtained for three relevant applications, and the future technology evolution to fulfill the requirements associated with more complexes and demanding applications.

This paper introduces a detailed analysis on the calculation of the absorption coefficient of multilevel uncooled infrared detectors. The analysis is carried out considering a two-level 25μm pixel pitch infrared detector with a sandwich type resistor which is divided into sub-regions consisting of different stacks of layers. The absorption coefficients of these different subregions are calculated individually by using the cascaded transmission line model, including the main body, arms, and the regions where the resistors are implemented. Then, the total absorption coefficient of the detector is found by calculating the weighted average of these individual absorption coefficients, where the areas of sub-regions are taken into account. The absorption can be calculated as a function of the sacrificial and structural layer thicknesses together with the sheet resistance of the absorber layer to find the optimum value. However, the thermal conductance of the detector must be considered while adjusting the structural layer thickness. The proposed analysis also takes the thermal conductance into account in order not to compromise the overall detector performance. Analysis shows that a maximum absorption coefficient of 0.92 for a specific two-level pixel can be obtained at the 10 μm wavelength, while the pixel results in a time constant of 11.3 ms with 27.2 nW/K thermal conductance in the thermal simulation. It is shown that the absorption coefficient of the pixel is maximized when the sheet resistance of the absorber is 380 Ω/sheet-resistance, which is almost equal to the free space impedance, as expected.

This paper introduces a detector biasing scheme proper for resistive microbolometer type uncooled thermal detector focal plane arrays (FPAs). The proposed scheme utilizes a 2-stage digital-to-analog converter (DAC) architecture where the first DAC stage generates the voltage interval that covers the bias voltage range of the overall FPA, while the second stage generates the high resolution analog voltages that are used to apply pixel-specific bias voltages. The second DAC stage output includes a resistive ladder type multi-level voltage generator (MLVG), which can be shared by multiple column readouts. The proposed scheme utilizes a single first stage DAC and a number of second stage DACs that can be optimized to meet the specifications of the application. The proposed scheme provides high resolution bias correction with small silicon area coverage, low power dissipation, and low noise. Furthermore, this scheme is suitable for microbolometer FPAs with very different detector resistance ranges, since the bias correction voltage interval is adjustable by the first DAC stage. The proposed architecture is used to design a 5+5 bit, 2-stage DAC that can be used in a 640x480 microbolometer FPA where a standard 0.35 μm CMOS process is considered. The simulation results show that the circuit provides a detector current resolution of 130 nA when the architecture is optimized to cover a 80 kΩ nominal detector resistance with ±10% resistance nonuniformity. The designed circuit dissipates 7.5 mW with a single 5 V supply, and the noise contribution to the detector current is 30 pA for a 10 kHz electrical bandwidth.

This paper introduces an optimization approach of thermal conductance for single level uncooled microbolometer detectors. An efficient detector design is required due to the limited availability of silicon area per pixel, i.e., the pixel pitch, and due to the capabilities of the fabrication line. The trade-offs between physical parameters are studied to attain the best performance, including the thermal conductance, the thermal time constant, the effective temperature coefficient of resistance (TCR), and the active area, where the main performance criterion has been selected as the Noise Equivalent Temperature Difference (NETD). A microbolometer pixel is modeled using theoretical formulations, and simulations are carried out using this model, and then, the accuracy of the model is verified by Finite Element Method (FEM) analysis. Consequently, optimum design parameters, such as the length of the support arms and the choice of interconnect metal can be extracted from the simulations for a defined process flow. Furthermore, a simple and reliable method for measuring the thermal conductance has been introduced. With this method, it is possible to accurately measure the thermal conductance in a large pixel temperature range, which is required especially for high thermal resistance microbolometers as they heat up rapidly in vacuum. The validity and accuracy of this method are also verified by comparing the simulation results with measurements performed on a single pixel microbolometer that is designed and fabricated based on the optimization approach outlined in this paper.

Driven by dramatic cost reduction of detectors, the market volume for thermography and infrared vision will triple by 2015. In our paper, we have both analyzed market and technical trends for uncooled infrared imagers' applications.

While InGaAs-based SWIR imaging technology has been improved dramatically over the past 10 years, the motivation remains to reduce Size Weight and Power (SWaP) for applications in Intelligence Surveillance and Reconnaissance (ISR). Goodrich ISR Systems, Princeton (Sensors Unlimited, Inc.) has continued to improve detector sensitivity. Additionally, SUI is working jointly with DRS-RSTA to develop innovative techniques for manufacturing dual-band focal planes to provide next generation technology for not only reducing SWaP for SWIR imagers, but also to combine imaging solutions for providing a single imager for Visible Near-SWIR (VNS) + LW imaging solutions. Such developments are targeted at reducing system SWaP, cost and complexity for imaging payloads on board UASs as well as soldier deployed systems like weapon sights. Our motivation is to demonstrate capability in providing superior image quality in fused LWIR and SWIR imaging systems, while reducing the total system SWaP and cost by enabling Short Wave and Thermal imaging in a single uncooled imager. Under DARPA MTO awarded programs, a LW bolometer (DRS-RSTA) is fabricated on a Short Wave (SW) InGaAs Vis-SWIR (SUI-Goodrich) Imager. The combined imager is a dual-band Sensor-Chip Assembly which is capable of imaging in VIS-SWIR + LW. Both DRS and Goodrich have developed materials and process enhancements to support these dual-band platform investigations. The two imagers are confocal and coaxial with respect to the incident image plane. Initial work has completed a single Read Out Integrated Circuit (ROIC) capable of running both imagers. The team has hybridized InGaAs Focal planes to 6" full ROIC wafers to support bolometer fabrication onto the SW array.

This paper describes a single-chip InGaAs SWIR camera with more than 120dB instant operational dynamic range with an innovative CMOS ROIC technology, so called MAGIC, invented and patented by New Imaging Technologies. A 320x256- pixel InGaAs 25μm pitch photodiode array, designed and fabricated by III-Vlab/Thales Research & Technology(TRT), has been hybridized on this new generation CMOS ROIC. With NIT's MAGIC technology, the sensor's output follows a precise logarithmic law in function of incoming photon flux and gives instant operational dynamic range (DR) better than 120 dB. The ROIC incorporates the entire video signal processing function including a CCIR TV encoder, so a complete SWIR InGaAs camera with standard video output has been realized on a single 30x30 mm² PCB board with ¼ W power consumption. Neither TEC nor NUC is needed from room temperature operation. The camera can be switched on and off instantly, ideal for all the portable battery operated SWIR band observation applications. The measured RMS noise and FPN noise on the prototype sensor in dark conditions are 0.4 mV and 0.27 mV respectively. The signal excursion from pixel is about 300mV over the 120 dB dynamic range. The FPN remains almost constant over the whole operation dynamic range. The NEI has been measured to be 3,71E+09 ph/s/cm² with 92 equivalent noise photons at 25Hz frame rate, better than the same architecture of InGaAs photodiode array hybridized on an Indigo ROIC ISC9809 with a pitch of 30 μm for which a readout noise of 120 electrons is observed.

Recent progress in short wavelength infrared MEMS based Fabry-Pérot microspectrometers at The University of Western Australia is presented. The original monolithic approach has been replaced with a hybrid one due to HgCdTe restricting the thermal budget and affecting the quality of structural silicon nitride films. The spectral resolution has been improved by introducing five layer Bragg mirrors and by limiting the electrostatically actuated top mirror bowing and tilting using stress balancing between layers. In effect the FWHM has been reduced to 30nm at ~2.0μm in comparison to the ideal theoretical mid-range value of 9nm. Analysis of mirror profiles shows that this difference is a result of remaining mirror imperfections.

InGaAs-based focal plane arrays are an unrivaled uncooled SWIR technology. Prior analytical models of InGaAs have been inaccurate at predicting the ultimate dark current limits for tight-pitch arrays. By going back to first-principles, we have developed an improved analytic model. This model clarifies how tight pitch arrays suppress diffusion current and why bulk generation-recombination is not a limiting factor in today's devices. We can thus explain our experimental arrays with dark currents of 0.5nA/cm2 at 20C and <0.1nA/cm2 at 7C as well why we believe another order of magnitude decrease in dark current is theoretically possible.

This paper reports the results of modeling of the electrical characteristics of SWIR/MWIR p-i-n photodiodes with type II InGaAs/GaAsSb multiple quantum wells (MQWs) as the absorption region. Bulk based model with the effective band gap of the type-II quantum well structure has been used in modeling of the experimental data. We investigated the dark current contributing mechanisms that are limiting the electrical performance of the diode. The quantitative simulation of the I-V characteristics shows, that the 200K to 290K performance of InGaAs/GaAsSb photodiodes is dominated by generation-recombination processes at the small reverse bias (-5V~0V). Above -10V, the trap-assisted tunneling current and direct tunneling current begin to dominate.

Infrared sensors with type II quantum well structure have gained great attention and have shown advanced progress. InGaAs/GaAsSb type II quantum well structures are considered as an attractive material system for realizing low dark current PDs owing to lattice-matching to InP substrate. In this report, we describe successful operation of PIN-PDs with InGaAs/GaAsSb quantum wells grown by metal-organic vapor phase epitaxy (MOVPE). MOVPE method is well-known to have good uniformity which leads to mass-production of focal plane array. Planer type pin-PDs were adopted. The p-n junction was formed in the absorption layer by the selective diffusion of zinc. Electrical and optical characteristics of pin-PDs such as well number dependence of responsivity, were investigated. Dark current was 9.0 μA/cm² at 233 K, which has better uniformity compared to those of MBE sample, and responsivity of 0.8 A/W in SWIR region were obtained. This result indicates that planer photodiode using MOVPE grown InGaAs/GaAsSb type II quantum wells is a promising candidate for consumer applications.

Aerius Photonics will present their latest developments in large InGaAs focal plane arrays, which are used for low light level imaging in the short wavelength infrared (SWIR) regime. Aerius will present imaging in both 1280x1024 and 640x512 formats. Aerius will present characterization of the FPA including dark current measurements. Aerius will also show the results of development of SWIR FPAs for high temperaures, including imagery and dark current data. Finally, Aerius will show results of using the SWIR camera with Aerius' SWIR illuminators using VCSEL technology.

SiOnyx has developed a novel silicon processing technology for CMOS sensors that will extend spectral sensitivity into the near/shortwave infrared (NIR/SWIR) and enable a full performance digital night vision capability comparable to that of current image-intensifier based night vision goggles. The process is compatible with established CMOS manufacturing infrastructure and has the promise of much lower cost than competing approaches. The measured thin layer quantum efficiency is as much as 10x that of incumbent imaging sensors with spectral sensitivity from 400 to 1200 nm.

This article explores the complex design challenges of optical imaging systems that can operate over a broad range of the electromagnetic spectrum, covering all bands from the visible to the far infrared simultaneously. Although the focus is placed on a refractive solution to these challenges, an effort to outline the limitations of reflective solutions is also presented. After exploring a novel method to optimize the choice of optical materials, an elegant and efficient example is provided: a refractive lens that is at once a total optical solution (one lens covering a broad spectral range) and a common aperture solution (one lens that works simultaneously with several camera types). This solution, StingRay Optics' own SuperBand^TM Optic, is ultimately explored in its functionality to address this need in an advantageous manner.

Infrared detector technology has progressed to include many fused wavebands. This has been driven by the need of military systems to image over diverse spectrums. Imaging systems can now operate in both the short wave infrared (SWIR) as well as the long wave infrared (LWIR). Reflective optics seems like a natural solution to such a large waveband, but they will have more restrictive size and field of view constraints. This paper will demonstrate the steps to achieve a Petzval lens with fast aperture and moderate field that is achromatic in the SWIR and has low axial color in the LWIR. The lens achieves a high resolution solution in terms of modulation transfer function (MTF).

This paper discusses the design and development of a dual field of view, all-refractive infrared optical system that images the mid-wave infrared (MWIR) light in one field of view and the short wave infrared (SWIR) light in the narrower second field of view onto the same detector. The narrow field of view images the SWIR radiation at a slow f/number of 10.0, while the wide field of view images the MWIR radiation at f/1.9. The field of view is changed via a single lens that changes its axial position within the lens, resulting in an axial zoom and an overall magnification change of 6X. The change in focal length and f/number at the same time enables an increased focal length without having to increase the aperture size by the ratio of the focal length change. The large field of view change is achieved by both the motion of the lens, and the use of the spectral properties of the materials that change with wavelength. The change in spectral bands is accomplished via the use of a spectral filter wheel.

In space infrared (IR) optics, to achieve better observation of ground target, a common aperture all-reflective telescope, working at fast focal-ratio with multi-channel to cover different waveband and wide field-of-view (FOV), is a most wanted optical system. The remarkable imaging properties of the fast focal-ratio, flat-field, anastigmatic, rotationally symmetric Schwarzschild telescope have been well recognized historically, but suffer strong central obscuration and limited FOV in the conventional axis-symmetric design. Our solution is to use an eccentric system evolved from the Schwarzschild axially symmetric system, adding a tertiary off-axis mirror, to optimize the off-axis performance with the appropriate system parameters and specs, as required by most space IR optical systems. The optical design system consists of three powered mirrors, in which the primary (M1) is convex and secondary (M2) is either convex or concave, with a tertiary (M3) always in concave shape respectively. Both secondary and tertiary mirrors have their size larger than that of the primary. The entrance pupil of the system is projected behind M1. Dichroic filters can be used after the tertiary mirror to achieve separation of multi-spectral channels. In the designs the mirrors with optimized aspherical shapes, which are all in even-asphere warped up to 10^th asphericities, are used for achieving the final image quality. The final corrected wavefront in the system can result in the good optical performance with an encircled energy of better than 80% per pixel for all channels, working at F/1.66 to correct a wide FOV up to 27.7⁰ (H) x 48.7⁰ (V). The design is scalable for different image scales, as usually required for different optical systems targeting different applications. The broad spectral range from mid-wave infrared (MWIR) up to Far IR can be fully covered by this design. Multiple focalplane- arrays (FPAs) can be used with respect to different spectral channels in the optical systems.

Homeland security systems, special forces, unmanned aerial vehicles (UAV), and marine patrols require low cost, high performance, multi-mode visible through infrared (VIS-IR) wavelength optical systems to identify and neutralize potential threats that often arise at long ranges and under poor visibility conditions. Long range and wide spectral performance requirements favor reflective optical system design solutions. The limited field of view of such designs can be significantly enhanced by the use of catadioptric optical solutions that utilize molded or diamond point machined VIS-IR lenses downstream from reflective objective optics. A common optical aperture that services multiple modes of field-of-view, operating wavelength, and includes laser ranging and spotting, provides the highest utility and is most ideal for size and weight. Such a design also often requires fast, highly aspheric, reflective, refractive, and sometimes diffractive surfaces using high performance and aggressively light-weighted materials that demand the finest of manufacturing technologies. Visible wavelength performance sets the bar for component optical surface irregularity on the order of 20 nm RMS and surface finishes less than 3.0 nm RMS. Aluminum mirrors and structures can also be precision machined to yield "snap together alignment" or limited compensation assembly approaches to reduce cost and enhance interchangeability. Diamond point turning, die cast and investment cast mirror substrates and structures, computerized optical polishing, mirror replication, lens molding and other advanced manufacturing technologies can all be used to minimize the cost of this type of optical equipment. This paper discusses the tradeoffs among materials and process selection for catadioptric, multi-mode systems that are under development for a variety of DoD and Homeland Security applications. Several examples are profiled to illuminate the confluence of applicable design and manufacturing technologies.

Today, both military and civilian applications require miniaturized optical systems in order to give an imagery function to vehicles with small payload capacity. After the development of megapixel focal plane array (FPA) with micro-sized pixels, this miniaturisation will become feasible with the integration of optical functions in the detector area. In the field of cooled infrared imaging system, the detector area is the Detector-Dewar-Cooler Assembly (DDCA). A dewar is a sealed environment where the detector is cooled on a cold plate. We show in this paper that an imagery function can be added to the dewar by simply integrating a single meniscus inside the cold shield. An infrared system with a wide field of view and high throughput is thus obtained without adding optics outside the dewar. The additional mass of the optic is sufficiently small to be compatible with the cryogenic environment of the DDCA. The temperature stabilization of the optic and the reduction of the background radiation are the main advantages of this system. The performance of this camera will be discussed and several evolutions of this camera will be introduced too.

We have recently shown that dewar-level integration of optics is a promising way to develop compact IR cameras. Indeed, the integration of optics into the dewar leads to simple and entirely cooled optical architectures dedicated to imaging applications with large-field of view. Here, we review the optical elements we could add in those devices to make a hyper- or multispectral imager. Among them, we find specific focal-plane arrays with a built-in spectrometry function, plasmonic filters combined with a multichannel optical design, and birefringent interferometers. Several optical architectures will be detailed with first experimental results.

Todays battlefield is using imaging systems everywhere, starting from simple observation systems and up to very sophisticate warning and offensive systems. Cameras are integrated in almost all systems. Regulation and control of optical power in cameras presently requires an electronic feedback control or offline data processing, which introduces complex and expensive systems. We present a non-linear, solid-state passive dynamic sunlight filter (DSF) performing this process, yielding similar results - passively. When sunlight intensity increases, the DSF transmission decreases according to the amount of the incident lights, resulting in a darkened state, which is limited only to the over exposed area. The area returns to transparency once the amount of light decreases below a threshold level. We demonstrate here new experimental results showing an increase in the camera's dynamic range when using the DSF.

In the 8-12 micron waveband Focal Plane Arrays (FPA) are available with a 17 micron pixel pitch in different arrays sizes (e.g. 512 x 480 pixels and 320 x 240 pixels) and with excellent electrical properties. Many applications become possible using this new type of IR-detector which will become the future standard in uncooled technology. Lenses with an f-number faster than f/1.5 minimize the diffraction impact on the spatial resolution and guarantee a high thermal resolution for uncooled cameras. Both effects will be quantified. The distinction between Traditional f-number (TF) and Radiometric f-number (RF) is discussed. Lenses with different focal lengths are required for applications in a variety of markets. They are classified by their Horizontal field of view (HFOV). Respecting the requirements for high volume markets, several two lens solutions will be discussed. A commonly accepted parameter of spatial resolution is the Modulation Transfer Function (MTF)-value at the Nyquist frequency of the detector (here 30cy/mm). This parameter of resolution will be presented versus field of view. Wide Angle and Super Wide Angle lenses are susceptible to low relative illumination in the corner of the detector. Measures to reduce this drop to an acceptable value are presented.

This work explores the influence of head window thickness on the performance of a mid-wave infrared, panoramic periscope imager. Our focus is on transparent spinel ceramic as the head window material. Spinel is an attractive material for IR applications due to its good strength and transmission properties (visible through mid-wave). However, there is some degradation in spinel transmission near the high end of the mid-wave band ( 5μm) as the head window thickness increases. In this work we predict the relationship between head window thickness and imager performance, as quantified by the Noise Equivalent Temperature Difference, and compare these predictions to values estimated from experimental data. We then discuss the implications for imager design and demonstrate a possible approach to correcting for the headwindow-induced losses. The imager used in this study is a compact, catadioptric, camera that provides a 360^o horizontal azimuth by -10^o to +30^o elevation field of view and uses a 2048 x 2048, 15μm pitch InSb detector.

As Chalcogenide glass and Precision Molded Optics (PMO) have developed and matured to a point of being accepted as replacements for Germanium Single Point Diamond Turned (SPDT) optics; technological research is being dedicated to developing infrared PMO that can be used in a broader application base. These include laser arrays, large aperture molded chalcogenide optics, and molded in mount infrared optics. This paper presents applications for infrared laser arrays and the corresponding optics that must be closely mechanically mounted to avoid clipping the beams. Different molding and mounting techniques will be discussed to solve this issue which include; dicing chalcogenide optic lenses, molded in mount chalcogenide optics and stepped optic shape molding for mounting purposes. Accompanying the research and discussion of these techniques will be experiments and molded chalcogenide glass lenses showing the results and application for each lens type.

A thermal imaging zoom system has been developed for the mid wave infrared band with greater than 30X zoom range. The zoom system provides continuous changes in the field of view from the narrow field of view to the wide field of view. Athermalization was also a key feature included in the design. An active thermal compensation approach is being used to cover a broad thermal range. A preloaded rail approach is used to maintain boresight and vibration requirements. The final optical layout and mechanical design resulted in a system suitable for tactical and other harsh environments. The current design is very compact for the extremely large zoom range but, the lens layout also provides adequate space for folding. In this way the zoom system can be easily configured for applications with compact space claims such as small turrets or gimbals. The fundamental optical design has also been found to be capable of accommodating different camera formats (focal plane array size and F number).

State of the art high performance cooled IR systems need to have more than just excellent E/O performance. Minimum size weight and power (SWaP) are the design goals to meet our forces' mission requirements. Key enabler for minimum SWaP of IR imagers is the operation temperature of the focal plane array (FPA) employed. State of the art MCT or InAsSb nBn technology has the potential to rise the FPA temperature from 77 K to 130-150 K (high operation temperature HOT) depending on the specific cut-off wavelength. Using a HOT FPA will significantly lower SWaP and keep those parameters finally dominated by the employed cryocooler. Therefore compact high performance cryocoolers are mandatory. For highest MTTF life AIM developed its Flexure Bearing Moving Magnet product family "SF". Such coolers achieve more than 20000 h MTTF with Stirling type expander and more than 5 years MTTF life with Pulse Tube coldfinger (like for Space applications). To keep the high lifetime potential but to significantly improve SWaP AIM is developing its "SX" type cooler family. The new SX040 cooler incorporates a highly efficient dual piston Moving Magnet driving mechanism resulting in very compact compressor of less than 100mm length. The cooler's high lifetime is also achieved by placing the coils outside the helium vessel as usual for moving magnet motors. The mating ¼" expander is extremely compact with less than 63 mm length. This allows a total dewar length from optical window to expander warm end of less than 100 mm even for large cold shields. The cooler is optimized for HOT detectors with operating temperatures exceeding 95 K. While this kind of cooler is the perfect match for many applications, handheld sights or targeting devices for the dismounted soldier are even more challenging with respect to SWaP. AIM therefore started to develop an even smaller cooler type with single piston and balancer. This paper gives an overview on the development of this new compact cryocooler. Technical details and performance data will be shown.

Joule-Thomson micro cryogenic coolers (MCCs) are a preferred approach for small and low power cryocoolers. With the same heat lift, MCC's power input can be only 1/10 of a thermoelectric cooler's input, and MCC's size can be only 1/10 of a Stirling cooler's size. With futuristic planar MCC and with high frequency MEMS compressors to be developed, its size can be reduced another order of magnitude. Such "invisible" cryocoolers may revolutionize future IR imaging systems. We will review our studies on the feasibility of MCC with an emphasis on: 1) high thermal isolation levels reaching 89,000 K/W; 2) custom-designed gas mixtures with refrigeration capabilities increased by 10X and pressure ratio reduced to only 4:1; 3) compressors with low pressure ratios; and 4) excellent scalability for further size reduction.

Cryogenic coolers are often used in modern spacecraft in conjunction with sensitive electronics and sensors of military, commercial and scientific instrumentation. The typical space requirements are: power efficiency, low vibration export, proven reliability, ability to survive launch vibration/shock and long-term exposure to space radiation. A long-standing paradigm of exclusively using "space heritage" equipment has become the standard practice for delivering high reliability components. Unfortunately, this conservative "space heritage" practice can result in using outdated, oversized, overweight and overpriced cryogenic coolers and is becoming increasingly unacceptable for space agencies now operating within tough monetary and time constraints. The recent trend in developing mini and micro satellites for relatively inexpensive missions has prompted attempts to adapt leading-edge tactical cryogenic coolers for suitability in the space environment. The primary emphasis has been on reducing cost, weight and size. The authors are disclosing theoretical and practical aspects of a collaborative effort to develop a space qualified cryogenic refrigerator system based on the tactical cooler model Ricor K527 and the Iris Technology radiation hardened Low Cost Cryocooler Electronics (LCCE). The K27/LCCE solution is ideal for applications where cost, size, weight, power consumption, vibration export, reliability and time to spacecraft integration are of concern.

The operation of the thermo-mechanical unit of a cryogenic cooler may originate a resonant excitation of the spacecraft frame, optical bench or components of the optical train. This may result in degraded functionality of the inherently vibration sensitive space-borne infrared imager directly associated with the cooler or neighboring instrumentation typically requiring a quiet micro-g environment. The best practice for controlling cooler induced vibration relies on the principle of active momentum cancellation. In particular, the pressure wave generator typically contains two oppositely actuated piston compressors, while the single piston expander is counterbalanced by an auxiliary active counter-balancer. Active vibration cancellation is supervised by a dedicated DSP feed-forward controller, where the error signals are delivered by the vibration sensors (accelerometers or load cells). This can result in oversized, overweight and overpriced cryogenic coolers with degraded electromechanical performance and impaired reliability. The authors are advocating a reliable, compact, cost and power saving approach capitalizing on the combined application of a passive tuned dynamic absorber and a low frequency vibration isolator. This concept appears to be especially suitable for low budget missions involving mini and micro satellites, where price, size, weight and power consumption are of concern. The authors reveal the results of theoretical study and experimentation on the attainable performance using a fullscale technology demonstrator relying on a Ricor model K527 tactical split Stirling cryogenic cooler. The theoretical predictions are in fair agreement with the experimental data. From experimentation, the residual vibration export is quite suitable for demanding wide range of aerospace applications. The authors give practical recommendations on heatsinking and further maximizing performance.

The advantages of the common Rotary Stirling cycle coolers over the Split Stirling Linear are the overall size, light weight, low cooler input power and high efficiency. The main disadvantage has always been self induced vibration. Self induced vibration is a major consideration in the design of stabilized IR imaging systems/(GIMBALS) due to the effect it has on image quality i.e. Jitter. The "irregular shape" of the Rotary cooling engine attached to the payload and optics is also a problem in terms of the limits it has on optical system size. To address these issues, FLIR Systems Inc in Boston MA, developed a new rotary Stirling cycle cooling engine known as the FLIR Submicro Cooler. The Submicro is now in production and has been applied in a few products especially in FLIR"S smallest GIMBAL which measures 7.0 inch in spherical diameter. In this paper we discuss the improvements made in terms of IDCA implementation in stabilized imaging systems.

Thales Cryogenics has an extensive background in developing and manufacturing Stirling rotary integral (Monobloc) coolers for military applications. Up to now, this cooler range was based on three coolers named RM2, RM3 and RM4. Due to specific market demands, a new type of cooler has recently been developed in the Rotary Monobloc range (RM): the RM1. This cooler has been designed for applications where a low cooling power and a high efficiency are required and is particularly suitable for cooling components with a low heat load at intermediate temperature (90 to 150K) while allowing short cool down time. Cooling down to 77K remains possible but is restricted in available cooling capacity. The RM1 shows high compactness and is the smallest and lightest cooler of the RM product range. RM1 has been designed to ease integration process. In this paper, an overview of RM1 performances is given as well as a description of features enabling easy integration. The RM1 cooler has been extensively qualified for use in various thermal and mechanical environments. Life time tests have been carried out on a sample batch of 9 coolers tested according to our accelerated life time test profile. The qualification results and the evolution of performances over time in life tests are reported. Finally, some specific considerations and results are given for intermediate temperature applications with cold temperatures up to 200K.

Thales Cryogenics (TCBV) has an extensive background in delivering long-life cryogenic coolers for military, civil and space programs. During the last years many technical improvements have increased the lifetime of coolers resulting in significantly higher MTTF's. Lifetime endurance tests are used to validate these performance increases. An update will be given on lifetime test of a selection of TCBV's coolers. MTTF figures indicate the statistical average lifetimes for a large population of coolers. However, for the user of IR camera's and spectrometers a detailed view on the performance of an individual cooler and the possible impact of its performance degradation during its lifetime is very important. Thales Cryogenics is developing Cooler Diagnostic Software (CDS), which can be implemented in the firmware of its DSP based cooler drive electronics. With this implemented software the monitoring of the main cooler parameters during the lifetime in the equipment will be possible, including the prediction of the expected cooler performance availability. Based on this software it will be possible to analyze the status of the cooler inside the equipment and, supported by the lifetime knowledge at Thales Cryogenics, make essential choices on the maintenance of equipment and the replacement of coolers. In the paper, we will give an overview of potential situations in which such a predictive algorithm can be used. We will present the required interaction with future users to make an optimal interaction and interpretation of the generated data possible.

The growing demand for EO applications that work around the clock 24hr/7days a week, such as in border surveillance systems, emphasizes the need for a highly reliable cryocooler having increased operational availability and decreased integrated system Life Cycle (ILS) cost. In order to meet this need RICOR has developed a new rotary Stirling cryocooler, model K508N, intended to double the K508's operating MTTF achieving 20,000 operating MTTF hours. The K508N employs RICOR's latest mechanical design technologies such as optimized bearings and greases, bearings preloading, advanced seals, laser welded cold finger and robust design structure with increased natural frequency compared to the K508 model. The cooler enhanced MTTF was demonstrated by a Validation and Verification (V&V) plan comprising analytical means and a comparative accelerated life test between the standard K508 and the K508N models. Particularly, point estimate and confidence interval for the MTTF improvement factor where calculated periodically during and after the test. The (V&V) effort revealed that the K508N meets its MTTF design goal. The paper will focus on the technical and engineering aspects of the new design. In addition it will discuss the market needs and expectations, investigate the reliability data of the present reference K508 model; and report the accelerate life test data and the statistical analysis methodology as well as its underlying assumptions and results.

L-3 CE has in place a continuous effort to evaluate and improve the lifetime of its cryocooler products. This effort includes analysis of both lab environment reliability tests and field data from shipped units. The purpose of this paper is to outline L-3 CE's life testing methodology and provide reliability data for L-3 CE cryocoolers, specifically for the 0.6- Watt Cooler (Model B602), 1.0-Watt Reduced Size, Weight, and Power (RSWAP) Cooler (Model B610), and the 1.5- Watt Cooler (Model B1500). Cooler performance characteristics such as cooldown time, refrigeration capacity, and input power are monitored throughout the life of the cooler. The data presented here updates previously reported data. Field data for the 1.0-Watt Cooler (Model B1000) is also presented.

Recent efforts have been paid to elevate the operating temperature of Type II superlattice Mid Infrared photon detectors. Using M-structure superlattice, novel device architectures have been developed, resulting in significant improvement of the device performances. In this paper, we will compare different photodetector architectures and discuss the optimization scheme which leads to almost one order of magnitude of improvement to the electrical performance. At 150K, single element detectors exhibit a quantum efficiency above 50%, and a specific detectivity of 1.05x10¹² cm.Hz^1/2/W. BLIP operation with a 300K background and 2π FOV can be reached with an operating temperature up to 180K. High quality focal plane arrays were demonstrated with a noise equivalent temperature difference (NEDT) of 11mK up to 120K. Human body imaging is achieved at 150K with NEDT of 150mK.

The XB_nn high operating temperature (HOT) detector project at SCD is aimed at developing a HOT (~150K) mid-wave infrared (MWIR) detector array, based on InAsSb/AlSbAs barrier detector or "bariode" device elements. The essential principle of the XB_nn bariode architecture is to suppress the Generation-Recombination contribution to the dark current by ensuring that the depletion region of the device is contained inside a large bandgap n-type barrier layer (BL) and excluded from the narrow bandgap n-type active layer (AL). The band profile of the XB_nn device leads to effective blocking of electron transport across the BL while maintaining a free path for the holes, thus assuring a high internal quantum efficiency (QE). Our devices exhibit a very large minority carrier lifetime (~700 ns), leading to a very low dark current of <10^-6 A cm^-2 at 150K, which is essentially diffusion limited. We compare bariode devices with both a p-type GaSb contact layer (CL) and an n-type InAsSb CL (termed C_pB_nn and nB_nn, respectively). Apart from a ~0.3V shift in the operating bias, the optical and electrical properties of both architectures are virtually identical, demonstrating the generic nature of the XB_nn barrier detector family. We have fabricated FPAs from nB_nn bariode arrays bonded both to a 320×256, 30 μm pitch Read-Out Integrated Circuit (ROIC) and a 640×512, 15 μm pitch ROIC. For lattice matched FPAs the cut-off wavelength at >50% of maximum response is ~ 4.1 μm. We show an image registered at 150K with a 640×512/15 μm Pelican FPA, using f/3.2 optics. The operability at 150K is >99.5% and the measured NETD, limited only by shot and Read-Out noise, is 20 mK for a 22 ms integration time. At this f/number, the detector has a background limited performance (BLIP) up to ~165K.

The Photon-Trap Structures for Quantum Advanced Detectors (PT-SQUAD) program requires MWIR detectors at 200 K. One of the ambitious requirements is to obtain high (> 80 %) quantum efficiency over the visible to MWIR spectral range while maintaining high D* (> 1.0 x 10¹¹ cm √Hz/W) in the MWIR. A prime method to accomplish the goals is by reducing dark diffusion current in the detector via reducing the volume fill ratio (VFR) of the detector while optimizing absorption. Electromagnetic simulations show that an innovative architecture using pyramids as photon trapping structures provide a photon trapping mechanism by refractive-index-matching at the tapered air/semiconductor interface, thus minimizing the reflection and maximizing absorption to > 90 % over the entire visible to MWIR spectral range. InAsSb with bandgap appropriate to obtaining a cutoff wavelength ~ 4.3 μm is chosen as the absorber layer. An added benefit of reducing VFR using pyramids is that no AR-coating is required. Compound-barrier (CB) detector test structures with alloy composition of the InAsSb absorber layer adjusted to achieve 200 K cutoff wavelength of 4.3 μm (InAsSb lattice-matched to GaSb). Dark current density at 200 K is in the low 10^-4 A/cm² at V_d = -1.0 V. External QE ~ 0.65 has been measured for detectors with a Si carrier wafer attached. Since illumination is through the Si carrier wafer that has a reflectance of ~ 30 %, this results in an internal QE > 0.9.

The unipolar barrier is a new approach for control of dark currents in infrared photodetectors. First demonstrated in the nBn detector and then in the unipolar barrier photodiode, unipolar barriers have been shown to block surface leakage current. Unipolar barriers can also be implemented to filter out dark current components such as Shockley-Read-Hall current, direct band-to-band tunneling and trap-assisted tunneling, but are not useful for blocking diffusion currents. Current density-voltage characteristics of molecular-beam-epitaxy-grown InAs based unipolar barrier photodiodes are presented and analyzed, showing effective limiting of noise current mechanisms for different unipolar barrier photodiode architectures. R_oA data shows near Auger-limited device performance and R_oA values in excess of 1x10⁷ Ω-cm².

Interband cascade (IC) infrared (IR) photodetectors (ICIPs) are a new type of infrared detectors based on quantum-engineered InAs/GaSb/AlSb heterostructures. They combine the features of conventional interband photodiodes with the discrete nature of quantum-well IR photodetectors (QWIPs). The operation of ICIPs takes advantage of fast intersubband relaxation and interband tunneling for carrier transport, and relatively slow interband transitions (long lifetime) for photon generation. As such, ICIPs can be optimized for specific application requirements, such as higher temperature operation or lower noise. By adopting a finite type-II InAs/GaSb superlattice (SL) as the absorber, we have demonstrated mid-IR ICIPs with low noise and photovoltaic operation. In this paper, we report some of our recent efforts in the development of mid-IR ICIPs for high temperature operations. The ICIP devices with a cut-off wavelength of 3.8 μm exhibit a resistance-area product of 2.65×10⁶ and 6.36×10³Ωcm² at 80 and 160 K, respectively.

Low size, weight and power (SWaP) are the most critical requirements for portable thermal imagers like weapon sights or handheld observations devices. On the other hand due to current asymmetrical conflicts there are high requirements for the e/o performance of these devices providing the ability to distinguish between combatants and non-combatants in adequate ranges. Despite of all the success with uncooled technology, such requirements usually still require cooled detectors. AIM has developed a family of thermal weapon sights called HuntIR and RangIR based on high performance cooled IR-modules which are used e.g. in the infantryman of the future program of the German army (IdZ). The specific capability of these devices is a high ID range >1500m for tank targets being suitable in use as thermal sights for .50 cal rifles like the G82, targeting units for the 40mm AGL or for night observation. While such ranges sound far beyond the operational needs in urban operations, the a.m. specific needs of asymmetric warfare require sometimes even more range performance. High operating temperature (HOT) is introduced in the AIM MCT 640x512/15μm MWIR or LWIR modules for further reduction of cooler power consumption, shorter cooldown times and higher MTTF. As a key component to keep performance while further reducing SWaP AIM is developing a new cooled MCT IR-module with reduced pitch of 12 μm operating at a temperature >120 K. The module will provide full TV format with 640x480 elements sensitive in the MWIR spectral band. The paper will show recent results of AIM IR-modules with high operating temperature and the impact of design regarding the IR-module itself and thermal sights making use of it.

Cooled IR technologies are challenged for answering new system needs like the reduction of power consumption. This reduction is requested in new IR system design in particular for cooled IR detection. The goal is to reduce system sizes, to increase system autonomies and reliabilities and globally to reduce system costs. One of the key drivers for cooled systems is the cooler and the operating temperature. As far as operating temperature is concerned, Sofradir and CEALETI LIR put a lot of efforts to increase the operating temperature of IR MCT detectors. The n/p and p/n MCT technologies are improved to operate at high temperature with good performances and particularly with low rate of defective pixels. These detectors operate in the MW blue band, MW and LW. In addition complex structures like nBn structures are developed to go further in the high operating temperature. Results are presented and discussed.

In this paper, a high operating temperature (HOT) broadband InAs/GaAs quantum dot (QD) infrared photodetector (QDIP) is reported. The QDIP covers a wide detection spectrum range from 3 μm to 10 μm. A large photoresponsivity of 12.0 A/W at a low bias voltage of 0.15V and a high peak specific photodetectivity D* of 1.2×10⁸ cmHz^1/2/W are obtained at a high operating temperature of 298 K.

Pelican-D is a new digital 640x512 / 15μm InSb detector developed by SCD to serve a number of applications. The Readout Integrated Circuit (ROIC) has a digital output which can be calibrated to a signal resolution in the 13-15 bit range. Besides the digital output, the detector has some additional advantages over other MWIR detectors of the same format. The high frequency of data output, which supports a full image frame rate of over 300Hz, is very useful in systems that track fast evolving events such as Missile Warning Systems (MWS), Missile Seekers and some Thermographic applications. Another important characteristic of the detector is related to an operation mode with relatively low readout noise. This mode of operation is especially beneficial in applications where the background radiation is low such as in long range surveillance systems. For imaging systems where very high sensitivity is required, the ROIC can be coupled to an epi-InSb detector array and have a dark current at 77K that is lower by a factor of 15 with respect to standard InSb. Alternatively, Pelican-D with epi-InSb can be operated at 95K with a standard dark current and sensitivity. Such an elevated operating temperature enables the use of cryogenic coolers of relatively low size, weight and power for applications such as Hand-held cameras, miniature gimbaled systems, and light UAVs. In this work we present in detail the characteristic performance of the new detector and its applications.

Raytheon is developing NIR sensor chip assemblies (SCAs) for scanning and staring 3D LADAR systems. High sensitivity is obtained by integrating high performance detectors with gain, i.e., APDs with very low noise Readout Integrated Circuits (ROICs). Unique aspects of these designs include: independent acquisition (non-gated) of pulse returns, multiple pulse returns with both time and intensity reported to enable full 3D reconstruction of the image. Recent breakthrough in device design has resulted in HgCdTe APDs operating at 300K with essentially no excess noise to gains in excess of 100, low NEP <1nW and GHz bandwidths and have demonstrated linear mode photon counting. SCAs utilizing these high performance APDs have been integrated and demonstrated excellent spatial and range resolution enabling detailed 3D imagery both at short range and long ranges. In the following we will review progress in real-time 3D LADAR imaging receiver products in two areas: (1) scanning 256 × 4 configuration for the Multi-Mode Sensor Seeker (MMSS) program and (2) staring 256 × 256 configuration for the Autonomous Landing and Hazard Avoidance Technology (ALHAT) lunar landing mission.

CEA-Leti has developed a dual mode infrared array detector for passive (thermal) or active 2D and 3D imaging. Very high sensitivity in 3D mode of operation is achieved by using an HgCdTe avalanche photodiode array with linear gain. The 30 μm pitch detector array is hybridized to a 320x256 pixels Readout Integrated Circuit (ROIC). In passive mode, the 3.6x10⁶ e- well capacity and the low noise of the ROIC allow to reach photon noise limited NETD. For active imaging mode, each pixel measures the time of arrival (3D) and the intensity (2D) of one laser pulse. A sensor based on a detector array with a cut off wavelength of 4.6μm at 80K was fabricated and tested. This paper describes the pixel architecture and presents ranging performances obtained in laboratory conditions. The first 2D and 3D active videos obtained during a field trial of our focal plane array are presented.

High-performance large-format detector arrays responsive to the 1-5μm wavelength range of the infrared spectrum fabricated using large area HgCdTe layers grown on 6-inch diameter (211) silicon substrates are available for advanced imaging applications. This paper reviews performance and capabilities of Raytheon Vision Systems (RVS) HgCdTe/Si Focal Plane Arrays (FPA) and shows 2k x 2k format MWIR HgCdTe/Si FPA performance with NEdT operabilities better than 99.9%. SWIR and MWIR detector performance for HgCdTe/Si is comparable to established performance of HgCdTe/CdZnTe wafers. HgCdTe devices fabricated on both types of substrates have demonstrated very low dark current, high quantum efficiency and full spectral band fill factor characteristic of HgCdTe. HgCdTe has the advantage of being able to precisely tune the detector cutoff via adjustment of the Cd composition in the MBE growth. The HgCdTe/Si detectors described in this paper are p-on-n mesa delineated architecture and fabricated using the same mature etch, passivation, and metallization processes as our HgCdTe/CdZnTe line. Uniform device quality HgCdTe epitaxial layers and application of detector fabrication processes across the full area of 6-inch wafers routinely produces high performing detector pixels from edge to edge of the photolithographic limits across the wafer, offering 5 times the printable area as costly 6×6cm CdZnTe substrates. This 6-inch HgCdTe detector wafer technology can provide applications demanding very wide FOV high resolution coverage the capability to produce a very large single piece infrared detector array, up to a continuous image plane 10×10 cm in size. Alternatively, significant detector cost reduction through allowing more die of a given size to be printed on each wafer is possible, with further cost reduction achieved through transition towards automated detector fabrication and photolithographic processes for both increased yields and reduced touch labor costs. RVS continues to improve its FPA manufacturing line towards achieving low cost infrared FPAs with the format, size, affordability, and performance required for current and future infrared applications.

This paper describes the status of MCT IR technology in France at Leti and Sofradir. This concerns first evolution of crystal growth of large CZT for substrates, and MCT epilayers grown by LPE and MBE. A focus will be made on extrinsic doping of MCT with Indium and Arsenic for device fabrication. Evolution of detector technology will also be considered for detectors that operate from NIR/SWIR to VLWIR, moving from an n on p vacancy doped technology to a fully extrinsically doped p on n device architecture. Last results on 3^rd generation detectors such as multicolor FPAs, HOT detectors and 2D or 3D FPAs that use MCT APD will also be described. Moving to larger FPAs, pixel pitch reduction become mandatory and technology evolution to achieve this goal will be presented .Then, cost reduction achievement through more compact systems that operate at higher temperature and/or integrate optical functions inside the cryostat will also be considered.

This paper describes the current state of the art HgCdTe grown by metal-organic vapour phase epitaxy on GaAs substrates, and progress in the development of dual-band (MW / LW) infrared detectors. We have described full-TV dual-band arrays of 640 x 512 pixels on 24μm and 20μm pitches. The latest development is a 20μm pitch 860 x 480 pixel array in 'widescreen' 16:9 format incorporating a new Read-Out Integrated Circuit (ROIC) designed in 0.35μm CMOS. The detector can be operated in multiple imaging modes: dedicated LW or MW, or both LW and MW wavebands per frame. The ROIC includes stable on-chip voltage references and a serial digital control interface. It supports integrate-then-read, integrate-while-read, binning and windowing readout modes. A proximity electronics board has been developed and is now offered to allow a range of detectors to be operated easily. Detector operation at higher operating temperatures has been demonstrated with a Hawk detector producing very high quality imagery up to 160K and useful imagery up to 175K.

3rd generation IR modules - dual-color (DC), dual-band (DB), and large format two-dimensional arrays - require sophisticated production technologies such as molecular beam epitaxy (MBE) as well as new array processing techniques, which can satisfy the rising demand for increasingly complex device structures and low cost detectors. AIM will extend its future portfolio by high performance devices which make use of these techniques. The DC MW / MW detectors are based on antimonide type-II superlattices (produced by MBE at Fraunhofer IAF, Freiburg) in the 384x288 format with a 40 μm pitch. For AIM, the technology of choice for MW / LW DB FPAs is MCT MBE on CdZnTe substrates, which has been developed in cooperation with IAF, Freiburg. 640x512, 20 μm pitch Focal Plane Arrays (FPAs) have been processed at AIM. The growth of MW MCT MBE layers on alternate substrates is challenging, but essential for competitive fabrication of large two-dimensional arrays such as megapixel (MW 1280x1024, 15 μm pitch) FPAs. This paper will present the development status and latest results of the above-mentioned 3rd Gen FPAs and Integrated Detector Cooler Assemblies (IDCAs).

The development of DB (Dual-Band) infrared detectors has been the core of research and technological improvements for the last ten years at CEA-LETI and Sofradir: the semi planar structure uses a proven standard process with robust reproducibility, leading to low-risk and a facilitated ramp-up to production. This makes it the natural choice for the third generation detectors proposed by Sofradir. The fabrication of DB MCT detectors is reaching maturity: ALTAIR with 24μm-pixel pitch arrays in TV format are available, showing median NETD around 18mK with operability over 99.5%. A second structure, based on two back to back diodes, with a single contact per pixel translates the DB pixel into smaller cell therefore being more efficient in terms of pitch reduction. These new technologies widen perspectives and open new horizons of applications such as large DB FPA, dual mode capability providing both SAL (Semi Active Laser) and IR operations for more robust target engagement or compact dual color detection with wide-angle integrated optics for missile warning system.

Reported is a detailed analysis of the dark current versus voltage versus temperature data of planar hetero-structure P⁺n mid wavelength infrared MWIR photodiodes with band gap energy E_g(78K) = 0.243 eV, λ_g= 5.1 μm and long wavelength infrared LWIR photodiodes with E_g(78K) = 0.115 eV, λ_g= 10.8 μm. The purpose of the investigations is to identify the dominant carrier recombination mechanisms and in particular to determine at what temperature and voltage is the onset of Shockley Read Hall (SRH) space charge currents. The important finding is that the currents can mostly be explained by a combination of Auger (e-e) and radiative carrier recombination processes with no evidence of SRH recombination through near mid-gap states; a lower bound estimate of the SRH lifetime for LWIR photodiode is 100 μs. Intrinsic radiative recombination is found to be the dominant carrier recombination mechanisms for the MWIR photodiode with a carrier concentration N_d=10¹⁵ cm^-3, and Auger (e-e) being dominant for the LWIR photodiode. The LWIR Auger (e-e) lifetime data is well fitted with the Beattie, Landsberg and Blakemore (BLB) formulas with a constant overlap integral F1F2= 0.15, which is in accord with recent electronic band structure calculations. From the analysis of variable area LWIR photodiodes the minority carrier conductivity mobility and diffusion length at 80K are calculated to be 350 cm²/V-s and 23 μm respectively. The LWIR lifetime measured by the photoconductive decay method is in agreement with the expected intrinsic Auger (e-e) lifetime ≈ 2 μs at 80K and with the lifetimes obtained from device analysis. For T ≤ 40K, trap assisted tunneling is the dominant current in reversed bias LWIR photodiodes; forward bias currents are dominated by diffusion currents of origin in the n- layer. For the MWIR photodiode deviation from diffusion limited behavior to G-R is observed at T < 80K and, the SRH lifetimes ιn0 and ιp0 are estimated to be 50 ms. Measured and calculated external quantum efficiencies at the peak responsivity wavelength λpk for both MWIR and LWIR photodiodes are ≈ 70% at 78K. For imaging in the 3-5 μm spectral band scene temperature 300K, F/3 optics, the noise equivalent temperature difference NE▵T of MWIR photodiodes is calculated to be near background limited performance BLIP =12.4 mK for detector temperatures Td ≤ 150K.

The influence of dislocations on the electrical and photo-electric characteristics of HgCdTe has been widely discussed in published literature. However, an unexplored aspect of the dislocations that has not yet attracted the attention of any of the investigators, is the band gap narrowing/widening induced by the intense stress field around dislocation core. Preliminary estimations show that the band gap narrowing due to the tensile region of the stress field along the dislocations in HgCdTe is high enough to cause significant band gap narrowing in low band gap HgCdTe. An enhanced Zener like band-to-band tunneling is proposed in the vicinity of dislocation cores. The calculations presented here qualitatively explain the observed influence of dislocations on HgCdTe photodiode characteristics.

The current-voltage and photo-response characteristics of middle wavelength infrared (MWIR) HgCdTe photodiodes have been performed based on a self-consistent solution of the Poisson's equation, the electron/hole continuity equations, and three generation-recombination processes as Auger, Shockley-Read-Hall and optical generation recombination. Three different carrier density approximations, (1) parabolic conduction band approximation, (2) Bebb's non-parabolic expression, and (3) Harman's non-parabolic approximation, are proposed to simulate the I-V curve and photo-response of MWIR HgCdTe photovoltaic devices by considering the carrier degeneracy and the non-parabolic conduction band. It is found that omitting non-parabolic effect can lead to an enormous deviation in the simulation result, especially for heavily doped HgCdTe devices. Based on the calculated results of photo-response, the parabolic conduction band and Harman's non-parabolic approximation can lead to the response peak shift to short and long wavelength, respectively.

This paper reports on the temperature-dependent extension of n-type inversion regions in HgCdTe photodiodes at low temperatures (87 K) compared to inversion regions at room temperature (300 K). Laser-beam-induced-current (LBIC) measurement techniques are used to obtain the photosensitive area extensions of n-type inversion in HgCdTe photodiodes for typical n+-on-p HgCdTe photovoltaic IR detectors. The effect of temperature on the extension of n-type conversion region is investigated by considering the sign of the LBIC signal. Theoretical results show that the hole concentration decreases in multi-doped HgCdTe as the temperature decreases. Consequently hole concentration is much lower than electron concentration at 87 K. It is demonstrated that the n-type inversion region extension is caused with the p-to-n type conversion.

Use of a dual band FPA necessitates an optical system that is capable of imaging both mid wave infrared (MWIR) and long wave infrared (LWIR) spectral bands simultaneously. Such optical system can have up to 10 lenses, (20 surfaces that require antireflection (AR) coatings) which, if 95% transmitting in each band, will result in overall throughput of just under 60%¹. With 99% transmitting in each band, overall throughput would be just over 90%, a relative improvement of 50%. An earlier paper presented dual band antireflection designs, as well as early fabrication attempts on plano Ge, ZnSe, ZnS, AMTIR-1, and CaF₂ windows². This paper presents results of prototype coating fabrication on ZnSe, Ge, and BaF₂ lenses that comprise a 7 lens set. The measured performance of the individual elements is used to model overall system performance. The elements were incorporated into an optical assembly and measured overall imager performance is analyzed and presented.

It is now well understood that with US Department of Defense (DoD) budgets shrinking and the Services and Agencies demanding new systems which can be fielded more quickly, cost and schedule are being emphasized more and more. At the same time, the US has ever growing needs for advanced capabilities to support evolving Intelligence, Surveillance and Reconnaissance objectives. In response to this market demand for ever more cost-effective, faster to market, single-channel, athermal optical systems, we have developed new metal polishing technologies which allow for short-lead, low-cost metal substrates to replace more costly, longer-lead material options. In parallel, the commercial marketplace is being driven continually to release better, faster and cheaper electronics. Growth according to Moore's law, enabled by advancements in photolithography, has produced denser memory, higher resolution displays and faster processors. While the quality of these products continues to increase, their price is falling. This seeming paradox is driven by industry advancements in manufacturing technology. The next steps on this curve can be realized via polishing technology which allows low-cost metal substrates to replace costly Silicon based optics for use in ultra-short wavelength systems.

ABB Bomem has recently designed a field-deployable reflectometer to measure the diffuse spectral reflectance of surfaces from 0.7 μm to 13.5 μm. Its spectral resolution is adjustable and can be as fine as 4 cm^-1. The instrument is designed to field and laboratory operation. It is portable and battery-operated. In its simplest mode, the instrument is automated and can be operated by non-specialist personnel with minimal training. The instrument was designed to build a spectral database of different surfaces in various conditions (different humidity, temperature, texture, mixing, etc.) and in the presence of various interfering chemicals (oils, solvents, etc.). The instrument has its own built-in infrared sources. The sources illuminate the ground area to be measured. The instrument has also two built-in reference diffusers: a Spectralon diffuser and an Infragold diffuser.

Since the early '90's CI has been involved in the development of FTIR hyperspectral imagers based on a Sagnac or similar type of interferometer. CI also pioneered the commercialization of such hyperspectral imagers in those years. After having developed a visible version based on a CCD in the early '90's (taken on by a spin-off company for biomedical applications) and a 3 to 5 micron infrared version based on a cooled InSb camera in 2008, it is now developing an LWIR version based on an uncooled camera for the 8 to 14 microns range. In this paper we will present design features and expected performance of the system. The instrument is designed to be rugged for field use, yield a relatively high spectral resolution of 8 cm^-1, an IFOV of 0.5 mrad., a 640x480 pixel spectral cube in less than a minute and a noise equivalent spectral radiance of 40 nW/cm²/sr/cm^-1 at 10μ. The actually measured performance will be presented in a future paper.

Infrared systems cameras trend is to require higher performance (thanks to higher resolution) and in parallel higher compactness for easier integration in systems. The latest developments at SOFRADIR / France on HgCdTe (Mercury Cadmium Telluride / MCT) cooled IR staring detectors do show constant improvements regarding detector performances and compactness, by reducing the pixel pitch and optimizing their encapsulation. Among the latest introduced detectors, the 15μm pixel pitch JUPITER HD-TV format (1280×1024) has to deal with challenging specifications regarding dewar compactness, low power consumption and reliability. Initially introduced four years ago in a large dewar with a more than 2kg split Stirling cooler compressor, it is now available in a new versatile compact dewar that is vacuum-maintenance-free over typical 18 years mission profiles, and that can be integrated with the different available Stirling coolers: K548 microcooler for light solution (less than 0.7 kg), K549 or LSF9548 for split cooler and/or higher reliability solution. The IDDCAs are also required with simplified electrical interface enabling to shorten the system development time and to standardize the electronic boards definition with smaller volumes. Sofradir is therefore introducing MEGALINK, the new compact Command & Control Electronics compatible with most of the Sofradir IDDCAs. MEGALINK provides all necessary input biases and clocks to the FPAs, and digitizes and multiplexes the video outputs to provide a 14 bit output signal through a cameralink interface, in a surface smaller than a business card.

Over the past few decades of computer aided engineering growth there has been much more progress in increasing the power and capability of function specific engineering tools (e.g., optical design, finite element analysis, etc.) than in the integration of and communication between these tools. With only a few notable exceptions, such as FEA being imbedded into solid modeling, the communication method between the function specific tools continues to be dominated by translation to neutral data formats (e.g., IGES, STEP) and file transfer. There are a number of problems with this approach. The translation is a serial process where an engineer has to stop at some point in the design, make the neutral file, send that file to the next function, and wait for feedback. The translation through a neutral format is typically one way so the whole translation process has to be repeated when changes are required. Revision tracking of multiple files for each design iteration is both critical and a likely source of errors. Also, as with any translation, some information is always lost or corrupted in the process. This paper describes some progress that has been made in more tightly integrating optical design, mechanical design, fabrication, and testing of optical systems. Tools have been developed that connect CODE V^®[1] to SolidWorks^®[2] (bidirectional), compensation of diamond turning CNC from interferometric data, slope analysis from interferometer and profilometer data, and other tools for wavefront error compensation, and electronic nulls. Design, machining, testing and inspection efficiency gains are achieved through tools that consume mechanical solid models in their native format.

In this paper we have investigated an approach to recognize thermal face images for face recognition using line features and Radial Basis Function (RBF) neural network as classifier for them. The proposed method comprises of three steps. In the first step, line features are extracted from thermal polar images and feature vectors are constructed using these line. In the second step feature vectors thus obtained are passed through eigenspace projection for the dimensionality reduction of feature vectors. Finally, the images projected into eigenspace are classified using a Radial Basis Function (RBF) neural network. In the experiments we have used Object Tracking and Classification beyond Visible Spectrum (OTCBVS) database. Experimental results show that the proposed approach significantly improves the verification and identification performance and the maximum success rate is 100% whereas on an average it is 94.44%.

In this paper, some basic principles and the implementing flow charts of a series of algorithms for target detecting are described. Then, according to actual needs and the comparison results of those algorithms, some of them are optimized in combination with the image pre-processing. On the foundation of above works, a moving target detecting and tracking software base on the OpenCV is developed by the software developing platform MFC. Three kinds of detecting algorithms are integrated in this software. These three detecting algorithms are Frame Difference method, Background Estimation method and Mixture Gaussian Modeling method. In order to explain the software clearly, the framework and the function are described in this paper. At last, the implementing processes and results are analyzed, and those algorithms for detecting targets are evaluated from the two aspects of subjective and objective. This paper is very significant in the application of the infrared target detecting technology.

Continuous improvements of quantum cascade laser (QCL) technology have extended the applications in environmental trace gas monitoring, mid-infrared spectroscopy in medicine and life science, law enforcement and homeland security and satellite sensor systems. We present the QCL based emissivity monitor for the CORSAIR blackbody. The emissivity of the blackbody was designed to be better than 0.9999 for the spectral range between 5 to 50μm. To actively monitor changes in blackbody emissivity we employ a QCL-based infrared illumination source. The illumination source consisted of a QCL and thermoelectric cooler (TEC) unit mounted on a copper fixture. The stability of the QCL was measured for 30, 60, and 90s operation time at 1.5A driving current. The temperature distribution along the laser mounting fixture and time dependent system heat dispersion were analyzed. The results were compared to radiative and conductive heat transfer models to define the potential laser operating time and required waiting time to return to initial temperature of the laser mount. The observed cooling behaviour is consistent with a primarily conductive heat transfer mechanism.

We report the operation of quantum cascade lasers (QCLs) as a mid-infrared (mid-IR) photo-detector under both photovoltaic and photoconductive modes. When operated at photoconductive mode, negative photo-conductance is observed at low bias current. The photo-conductance of the device changes from negative to positive when the bias is increased over a transparency point. These interesting mid-IR detection characteristics of QCL gain material can help and simplify the design and testing of mid-IR photonic integrated devices and circuits by using them to measure the coupling and waveguide loss and provide gain at any location in a mid-IR photonic circuit.

In previous papers to this SPIE forum the development of novel technology for next generation PIR security sensors has been described. This technology combines the mosaic pixel FPA concept with low cost optics and purpose-designed readout electronics to provide a higher performance and affordable alternative to current PIR sensor technology, including an imaging capability. Progressive development has resulted in increased performance and transition from conventional microbolometer fabrication to manufacture on 8 or 12 inch CMOS/MEMS fabrication lines. A number of spin-off applications have been identified. In this paper two specific applications are highlighted: high performance imaging IRFPA design and forest fire detection. The former involves optional design for small pixel high performance imaging. The latter involves cheap expendable sensors which can detect approaching fire fronts and send alarms with positional data via mobile phone or satellite link. We also introduce to this SPIE forum the application of microbolometer IR sensor technology to IoT, the Internet of Things.

In various military, space and civilian infrared applications, there is an important need for fast prototyping. For example, detectors with small pitch compared to the diffraction limited spot radius are now available and their specificities must be studied to optimize the design of the next imaging systems. At the very heart stands a requirement for flexible camera modules that provide a multitude of output formats as well as fast adaptability. Based on this concept, INO has developed an advanced compact camera module IRXCAM that can provide both raw data as well as fully processed images under a variety of outputs: NTSC, DVI, VGA, GigE and Camera Link. This tool can be used to perform a rapid demonstration of concept for a specific application. IRXCAM now supports the bolometric detectors INO IRM160A (160 x 120 52 μm pitch pixels, LWIR and THz), Ulis 04 17 1 (640 x 480 25 μpitch pixels, LWIR) and Ulis 05 25 1 (1024 x 768 17 μm pitch pixels). Reduction of the pixel pitch is a way to improve the compromise between the spatial resolution and the dimensions of an imaging system, mainly by reducing the required optical focal length with constant numerical aperture. Microscanning is another way that provides excellent results in terms of spatial resolution for pixel pitches as small as 25 μm in the LWIR range for F/1 optics. Microscanning also preserves the field of view without increasing the number of pixels of the detector. Finally, microscanning is an efficient way to reduce the aliasing effect of a non unity filling factor, a parameter that becomes increasingly important for small pixels. This paper presents the IRXCAM-1024 camera module, its performances, and its use for microscanning with 17 μm pitch pixels and commercial F/1 and F/0.86 refractive optical lenses.

The residual non uniformity of IR detectors is of major concern in the implementation of innovative IR systems. Several algorithms were developed during the last decade in order to solve this problem. One of these algorithms, "Scene based non uniformity correction" (SBNUC), is based on the notion that for a moving thermal imager, close by pixels get over time similar distributions of scene radiation. Following this assumption, differences between the time collected histograms of pixels are due to non uniformity and can thus be corrected. However, pixels which are not in the closest proximity of each other need in general more time for their histograms to match. Moreover, depending on the imager motion characteristics, there can be additional temporal and spatial limitations. An efficient SBNUC algorithm must take the exact limitations into consideration. In this work the SBNUC spatial-temporal relations are investigated using the spatial frequency domain representation. This representation provides an effective point of view since distances in the image are naturally translated into different spatial frequencies. We show that a way to implement this correction by a recursive time filter incorporates spatial frequency dependence into the correction speed, allowing the spatial-temporal relation to be engineered easily into the correction process. Using several characteristic imager motion models we analyze the effect of the motion on the spatialtemporal relations and demonstrate how an optimal SBNUC process can be designed, for each motion model.

Infrared (IR) detectors are enormously important for various applications including medical diagnosis, night vision etc. The current bottleneck of high-sensitive IR detectors is the requirement of cryogenic cooling to reduce the noise. Carbon nanotubes (CNTs) exhibit low dark current which allows CNTs to work without cooling. This paper presents the development of noncryogenic cooled IR focal plane array (FPA) using CNTs. The FPA consists of an array of CNTbased IR detectors which are sensitive to IR signal at room temperature. The CNT-based detectors can be made by our nanomanufacturing process. And the sensitivity of the detectors at a special wavelength can be achieved by selecting and controlling the bandgap of CNTs during the process. Besides, a readout circuitry has been integrated with the FPA to retrieve signals from the detectors for high throughput applications.

Ceramic thermistors like VO_x, amorphous Si, and NiMn₂O₄ are used for thermal sensing applications such as microbolometers and infrared sensors. These materials should have large temperature coefficient of resistance (TCR), high sensitivity, and low noise for these applications. Nickel manganite films have large TCR (>-3%/K) and good environmental stability, so that the properties are robust during subsequent processing. To improve the ability to prepare manganite spinels on pre-existing circuitry, new techniques that enable low-temperature depositions need to be developed. To address this, the spin spray technique was adopted in this work; this approach is both low cost and permits low process temperatures (<100^oC). Spin spray deposition is accomplished using two dilute water-based solutions: a reaction solution and oxidizing solution. The reaction solution consists of metal salts like nickel chloride and manganese chloride while the oxidizing solution contains pH buffer, pH adjuster, and oxidizing agent. To grow films, the solution was nebulized by a nitrogen carrier gas and sprayed onto a rotating silicon substrate with a 1μm thick SiO₂ buffer layer. As-deposited nickel manganite films were identified as nanocrystalline spinel by TEM analysis. The TCR values of nickel manganite film and nickel copper manganite film were about -3.6 %/K and -2.9 %/K respectively. Adding Cu allowed the electric resistivity to be tuned to less than 1000 Ω-cm. The normalized Hooge parameter was around 1.7x10- ²¹ cm³.

Reactive pulsed DC sputtering was used to grow a systematic series of films with resistivity ranging from 1 × 10^-3 to 6.8 × 10⁴ Ohm cm and TCR varying from 0 to -4% K-1. Throughout the parameter space studied a transition from amorphous to nano-crystalline growth was observed. Films in the resistivity range of interest for microbolometers contained a FCC VOx (0.8 < x < 1.3) phase. Altering the sputtering energetics via substrate biasing resulted in highlycolumnar, nano-twinned grains of FCC VO_x, providing a microstructure reminiscent of ion beam sputtered bolometer material. Electron diffraction in the TEM confirmed the presence of a secondary, oxygen-rich amorphous phase. Micro- Raman spectroscopy, which was also found to be sensitive to the secondary amorphous phase, was used to probe the chemical composition and morphology of VO_x thin films. Raman spectra from high resistivity amorphous films show a broad feature around ~890 cm^-1, while spectra from lower resistivity nano-crystalline films exhibit this same amorphous feature and a second broad feature at ~320 cm^-1. The resulting microstructure can be described as a nano-composite material composed of a low-resistivity crystalline phase embedded in a high-resistivity amorphous matrix. Our results suggest that both phases are required to achieve a high TCR, low resistivity material.

Hydrogenated silicon (Si:H) and germanium (Ge:H) are assessed for use as the resistive sensing layer in uncooled infrared microbolometer applications. N-type doped Si:H and undoped Ge:H thin films have been deposited using plasma enhanced chemical vapor deposition (PECVD) and monitored during growth using in situ, real time spectroscopic ellipsometry (RTSE) to track changes in the growth evolution and structure occurring within a single film as a function of thickness. Amorphous germanium (a-Ge) films prepared by sputtering and amorphous n-type doped silicon carbon alloy films (a-Si_1-xCx:H) films prepared by PECVD have also been studied by ex situ spectroscopic ellipsometry. Variations in the electrical properties of interest including film resistivity, temperature coefficient of resistance, and 1/f noise character in the form of the normalized Hooge parameter have been tracked as a function of the structure of the material as determined by deposition conditions and characterized by spectroscopic ellipsometry. Such notable variations observed include the effects of transitioning from amorphous to microcrystalline material in n-type Si:H; the addition of carbon to increase disorder in n-type a-Si:H; effects of process parameters for sputtered a-Ge; and a comparison of n-type a-Si:H, ntype a-Si_1-xCx:H, and undoped a-Ge:H properties for films all prepared by PECVD.

This paper gives a survey of both the design and essential properties of newly developed pyroelectric linear arrays made on the basis of lithium tantalate (LiTaO₃). There are up to 256 pixels with a minimum pitch of 50 μm. The detector is a hybrid arrangement of pyroelectric detector chip and 0.8 μm CMOS read-out circuit in a hermetic metal housing. Thanks to the development of a new black coating technology the thermal resolution and the homogeneity of the spectral responsivity have been permanently improved. The absorption layer consists of a columnar NiCr thin film. It is deposited using a special GLAD technology in high vacuum. The band absorption coefficient in the wavelength range 1...15 μm is about 0.9 for a layer with a thickness of about 1 μm. The NiCr absorption layer has very low thermal mass and high temperature stability. It can be patterned by lift-off technology. The measurement results demonstrate the excellent homogeneity of the spectral responsivity and the improvement of the signal-to-noise ratio of the linear arrays.

This paper will show that with our new readout approach, thermopile focal plane arrays can now reach the necessary LWIR performance levels that have been set by current microbolometer technology. Moreover, this paper shows that these new focal plane arrays can be made in commercial foundries using standard low cost CMOS. Besides improved performance, the additional benefit afforded by using these advanced thermopile focal plane arrays will be a simpler, more robust instrument. These attributes translate directly to lower cost and greater commercial potential. Detailed modeling shows that 25 μm, 17 μm and 12μm pitch thermopile focal plane arrays compare favorably in performance (NETD, τth) against microbolometer focal plane arrays with similar array size and detector geometry. The benefit of using thermopile focal plane arrays is the near elimination of 1/f noise and offset drift which has plagued microbolometers from their inception. Because of this noise reduction, shutterless operation should be possible. It is also shown that high performance thermoelectric materials are compatible with post- CMOS MEMS processes which, again, compares favorably to microbolometer focal plane arrays. Due to the potential lower system cost with thermoelectrics, these focal plane arrays could provide the path to deliver very low cost, high volume infrared imaging devices.

The structural, electronic, and optical properties of amorphous InSb and InAs_0.3Sb_0.7 films deposited on Corning glass, Al₂O₃ CdZnTe, SiO₂-Si, and CaF2 substrates by Radio Frequency (RF) magnetron sputtering have been studied as they relate to Mid and Long Wavelength Infrared (MWIR and LWIR) detection. Depositions at elevated substrate temperature and pressure of <10mTorr Ar show an emergence of crystalline grains with strong X-ray diffraction peaks at the (111) and (220) orientations. Electronically the amorphous InSb and InAs_0.3Sb_0.7 films deposited at 300K show hopping conduction with resistance in InSb ranging from 44 to 1.1E8 Ω-cm at 300K and 84K respectively. Optical analysis using Fourier transform infrared spectroscopy (FTIR) show the absorption of these films has an absorption tail, the equation of which differing activation energies in InSb and InAs0.3Sb0.7. Amorphous InSb and InAs_0.3Sb_0.7 films showed thermal responsivity in excess of 100V/W for 6μm thick films held at 233K. The maxima and minima of the responsivity are shown to correspond to the interference fringes in the film. The response is highly substrate dependent and compares favorably to other thermal detectors.

This paper provides results from testing and analysis of sun exposure effects on amorphous silicon (α-Si) microbolometers and vanadium oxide (VOX) microbolometers. Gain and offset changes for each detector type is provided. Results from different sun exposure levels corresponding to different geographic locations and time of year are presented. Data associated with increasing exposure duration and number of exposures is presented. The time constants associated with the sun exposure effects are also provided. Potential mitigation processes and algorithms are explored reducing the impact on image quality. The effectiveness of mitigation processes and algorithms is presented.

SiGe based focal plane arrays offer a low cost alternative for developing visible- near-infrared focal plane arrays that will cover the spectral band from 0.4 to 1.6 microns. The attractive features of SiGe based foal plane arrays take advantage of silicon based technology that promises small feature size, low dark current and compatibility with the low power silicon CMOS circuits for signal processing. This paper discusses performance characteristics for the SiGe based VIS-NIR Sensors for a variety of defense and commercial applications using small unit cell size and compare performance with InGaAs, InSb, and HgCdTe IRFPA's. We present results on the approach and device design for reducing the dark current in SiGe detector arrays. The electrical and optical properties of SiGe arrays at room temperature are discussed. We also discuss future integration path for SiGe devices with Si-MEMS Bolometers.