This PDF file contains the front matter associated with SPIE Proceedings Volume 10404 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

Measurements of low-frequency noise of type-II superlattice detectors designed for mid-IR wavelengths are used to determine noise limitations, calculate the real detectivity, and study 1/f noise-current correlations in these devices. No 1/f noise connected to the diffusion current is found as opposed to the generation-recombination, shunt, and tunneling currents. The contribution from the shunt current to 1/f noise can be so large that shunt-originated noise dominates in the high-temperature region, in which current is limited by the generation-recombination and diffusion components. It is also demonstrated that devices made of type-II superlattice contain traps generating random processes with thermally activated kinetics, and the activation energies of these traps are determined.

In this paper interband cascade type-II InAs/GaSb superlattice photodetector in temperature range from 225 K to 300 K is investigated. The article concerns the theoretical simulations of the detectivity characteristics of cascade detector with equal absorber regions in each stage. The obtained theoretical characteristics are comparable to experimentally measured, assuming that transport in absorber is determined by dynamics of intrinsic carriers. The greatest fit is observed for overlap values which increase with decreasing temperature form 0.175 eV for 225 K to 0.132 eV for 300 K.

Type-II strained-layer superlattices (T2SLs) are receiving increased interest as mid-wave infrared (MWIR) and long-wave infrared detector absorbers due to their potential Auger suppression and ability to be integrated into complex device structures. Although T2SLs show promise for use as infrared detectors, further investigation into the effects of high energy particle radiation is necessary for space-based applications. In this presentation, the effects of both 4.5 MeV and 63 MeV proton radiation on the carrier lifetime of MWIR InAs/InAsSb T2SLs will be shown. The 63 MeV proton radiation study will focus on the carrier lifetime of MWIR InAs/InAsSb T2SL samples of varying donor density. These results reveal a Shockley-Read-Hall (SRH) lifetime associated with a radiation induced defect level, which is not dependent on the donor density of the T2SL. Using 4.5 MeV proton radiation, the dependence of carrier lifetime on relative trap density in MWIR T2SLs samples is studied by varying the particle fluence. A comparison of these two radiation studies shows similar lifetime effects that will be discussed in detail. These results give insight into the viability of Ga-free T2SLs for space applications.

We present a model for the spectral external quantum efficiency (EQE) to extract the minority carrier diffusion length (L_n) of a unipolar nBp InAs/GaSb Type-II superlattice (T2SL) mid-wave infrared (MWIR) detector. The detector consists of a 4 μm thick p-doped 10ML InAs/10ML GaSb SL absorber with a 50% cut-off wavelength of 5 μm at 80 K and zero bias. The n-type doped InAs/AlSb SL barrier in the structure was included to reduce the GR dark current. By fitting the experimentally measured EQE data to the theoretically calculated QE based on the solution of the drift-diffusion equation, the p-type absorber was found the have L_n = 10 ± 0.5 μm at 80K, and L_n = 12 ± 0.5 μm at 120K and 150K. We performed the absorption coefficient measurement at different temperatures of interest. Also, we estimated the reduced background concentration and the built-in potential by utilizing a capacitance-voltage measurement technique. We used time-resolved-photoluminescence (TRPL) to determine the lifetime at 80K. With the result of the model and the lifetime measurement, we calculated the diffusion coefficient and the mobility in the T2SL detector at various temperatures. Also, we studied the behavior of different dark current mechanisms by fitting the experimentally measured and simulated dark current density under different operating temperatures and biases.

Compared to the highly sensitive silicon based affordable visible light detectors, infrared photodetectors require significant improvement. Localized surface plasmon resonances of metal nanoparticles can be utilized for increasing the absorption efficiency of semiconductors suited for detection of infrared radiation. In this work, plasmonic gold nanorods (AuNRs) are used to enhance generation of charge carriers and photon emission by InAs/InGaAs/GaAs quantum dots-in-a-well semiconductor heterostructures. Comparison of measured and calculated scattering spectra reveals that the AuNRs on GaAs exhibit red to green colors depending on their proximity to the GaAs surface. On the other hand, theoretical and experimental near-field optical characterization show that the electric field is tightly localized at the AuNR-GaAs interfacial regions, creating a convenient platform for investigating localized carrier generation and diffusion by monitoring the emission of InAs QDs. The carrier generation and photon emission enhancement is studied as a function of the GaAs thickness (distance) and temperature. Analysis of the QD emission enhancement as a function of distance reveals a Förster radius of 3.85 ± 0.15 nm, a near-field decay length of 4.8 ± 0.1 nm and an effective carrier diffusion length of 64.0 ± 3.0 nm. These distance parameters indicate two emission enhancement mechanisms: plasmon enhanced carrier generation inside the GaAs layer and diffusion to the InAs QDs, and direct near-field excitation of the InAs/InGaAs quantum well. The emission enhancement increases with temperature, confirming the importance of charge carrier diffusion from the GaAs to the InAs QDs, where recombination and photon emission takes place.

The given paper analyzes principles of interaction and analysis of the reflected optical radiation from biotissue in the process of assessment of regional hemodynamics state in patients with local hypertensive- ischemic pain syndrome of amputation stumps of lower extremities, applying the method of photoplethysmography.
The purpose is the evaluation of Laser photoplethysmography (LPPG) diagnostic value in examination of patients with chronic ischemia of lower extremities. Photonic device is developed to determine the level of the peripheral blood circulation, which determines the basic parameters of peripheral blood circulation and saturation level. Device consists of two sensors: infrared sensor, which contains the infrared laser radiation source and photodetector, and red sensor, which contains the red radiation source and photodetector. LPPG method allows to determined pulsatility of blood flow in different areas of the foot and lower leg, the degree of compensation and conservation perspectives limb.
Surgical treatment of local hypertensive –ischemic pain syndrome of amputation stumps of lower extremities by means of semiclosed fasciotomy in combination with revasculating osteotrepanation enabled to improve considerably regional hemodynamics in the tissues of the stump and decrease pain and hypostatic disorders.

The cross-section of a metallic sample was photoacoustically imaged using a pulsed nanosecond laser as the excitation source and a fiber-optic hydrophone system to acquire the pressure signal. The ultrasound sensor was an extrinsic Fabry-P´erot fiber-optic interferometer and the band-limited photodetected output signal was recorded in a digital oscilloscope. In order to reconstruct the image, a time set of ultrasound signals acquired in a circular scan around the sample were used to solve the time-reversal equations. It was observed that image contrast can be enhanced considering the deconvolution of the sensor frequency response from each measured pressure signal.

The extended InGaAs short wavelength infrared (SWIR) detector covers 1.0-2.5 μm wavelength, which plays an important role in weather forecast, resource observation, low light level systems, and astronomical observation and so on. In order to fabricate the high performance extended InGaAs detector, materials structure and parameters were characterized with Scanning Capacitance Microscopy (SCM), Scanning Spreading Resistance Microscopy (SSRM), the spreading of minority carriers and lattice quality were obtained. Mesa etching process, etching damage restoration technique and low temperature passivation technique were used in the fabrication of the extended InGaAs detector. The improvement of material structure and device process was studied by fabricating and measuring different perimeter-to-area (P/A) photodiodes and singledevice, respectively. The dark current density of the extended InGaAs detector obviously was reduced, about 2 nA/cm² at 170 K. The 512×256 FPAs were fabricated, the peak detectivity and the quantum efficiency of which are 5×10¹¹ cmHz^1/2/W and 80%, respectively. The staring image yielded of the 512×256 FPAs is shown, which demonstrates very good imaging quality.

The spectral irradiance of moonlight and air glow is mainly in the wavelength region from visible to short-wave infrared (SWIR) band. The imaging over the wavelength range of visible to SWIR is of great significance for applications such as civil safety, night vision, and agricultural sorting. In this paper, 640×512 visible-SWIR InGaAs focal plane arrays (FPAs) were studied for night vision and SWIR imaging. A special epitaxial wafer structure with etch-stop layer was designed and developed. Planar-type 640×512 InGaAs detector arrays were fabricated. The photosensitive arrays were bonded with readout circuit through Indium bumps by flip-chip process. Then, the InP substrate was removed by mechanical thinning and chemical wet etching. The visible irradiance can reach InGaAs absorption layer and then to be detected. As a result, the detection spectrum of the InGaAs FPAs has been extended toward visible spectrum from 0.5μm to 1.7μm. The quantum efficiency is approximately 15% at 0.5μm, 30% at 0.7μm, 50% at 0.8μm, 90% at 1.55μm. The average peak detectivity is higher than 2×1012 cm·Hz^1/2/W at room temperature with an integrated time of 10 ms. The Visible-SWIR InGaAs FPAs were applied to an imaging system for SWIR and visible light imaging.

The short-wavelength infrared (SWIR) InGaAs focal plane array (FPA) detector consists of infrared detector chip, readout integrated circuit (ROIC), and flip-chip bonding interconnection by Indium bump. In order to satisfy space application requirements for failure rates or Mean Time to Failure (MTTF), which can only be demonstrated with the large number of detectors manufactured, the single pixel in InGaAs FPAs was chosen as the research object in this paper. The constant-stress accelerated life tests were carried out at 70°C，80°C，90°C and100°C. The failed pixels increased gradually during more than 14000 hours at each elevated temperatures. From the random failure data the activation energy was estimated to be 0.46eV, and the average lifetime of a single pixel in InGaAs FPAs was estimated to be longer than 1E+7h at the practical operating temperature (5°C).

Space applications are requiring low dark current in the long wave infrared at low operating temperature for low flux observation. The applications envisioned with this type of specification are namely scientific and planetary missions. Within the framework of the joint laboratory between Sofradir and the CEA-LETI, a specific development of a TV format focal plane array with a cut-off wavelength of 12.5μm at 40K has been carried out. For this application, the p on n technology has been used. It is based on an In doped HgCdTe absorbing material grown by Liquid Phase Epitaxy (LPE) and an As implanted junction area. This architecture allows decreasing both dark current and series resistance compared to the legacy n on p technology based on Hg vacancies. In this paper, the technological improvements are briefly described. These technological tunings led to a 35% decrease of dark current in the diffusion regime. CEA-LETI and Sofradir demonstrated the ability to use the p on n technology with a long cutoff wavelength in the infrared range.

SiGe p-i-n photodetectors have been fabricated on 300 mm (12”) diameter silicon (Si) wafers utilizing high throughput, large-area complementary metal-oxide semiconductor (CMOS) technologies. These Ge photodetectors are designed to operate in room temperature environments without cooling, and thus have potential size and cost advantages over conventional cooled infrared detectors. The two-step fabrication process for the p-i-n photodetector devices, designed to minimize the formation of defects and threading dislocations, involves low temperature epitaxial growth of a thin p⁺ (boron) Ge seed/buffer layer, followed by higher temperature deposition of a thicker Ge intrinsic layer. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) demonstrated uniform layer compositions with well defined layer interfaces and reduced dislocation density. Time-of-flight secondary ion mass spectroscopy (TOF-SIMS) was likewise employed to analyze the doping levels of the p⁺ and n⁺ layers. Current-voltage (I-V) measurements demonstrated that these SiGe photodetectors, when exposed to incident visible-NIR radiation, exhibited dark currents down below 1 μA and significant enhancement in photocurrent at -1 V. The zero-bias photocurrent was also relatively high, showing a minimal drop compared to that at -1 V bias.

Improving sensitivity in the infrared spectrum is a challenging task. Detecting infrared light over a wide bandwidth and at low power consumption is very important. Novel solutions can be acquired by mimicking biological eyes such as compound eye with many individual lenses inspired from the nature. The nature provides many ingenious approaches of sensing and detecting the surrounding environment. Even though compound eye consists of small optical units, it can detect wide-angle electromagnetic waves and it has high transmission and low reflection loss. Insects have eyes that are superior compared to human eyes (single-aperture eyes) in terms of compactness, robustness, wider field of view, higher sensitivity of light intensity and being cheap vision systems. All these desired properties are accompanied by an important drawback: lower spatial resolution. The first step to investigate the feasibility of bio-inspired optics in photodetectors is to perform light interaction with the optical system that gather light and detect it. The most common method used in natural vision systems is the ray analysis. Light wave characteristics are not taken into consideration in such analyses, such as the amount of energy at the focal point or photoreceptor site, the losses caused by reflection at the interfaces and absorption cannot be investigated. In this study, we present a bio-inspired optical detection system investigated by wave analysis. We numerically model the wave analysis based on Maxwell equations from the viewpoint of efficient light detection and revealing the light propagation after intercepting the first interface of the eye towards the photoreceptor site.

We describe an interferometric technique capable of fully characterizing the optical response of few-mode and multi-mode detectors using only power measurements, and its implementation at 1550 nm wavelength. EnergyAbsorption Interferometry (EAI) is an experimental procedure where the system under test is excited with two coherent, phase-locked sources. As the relative phase between the sources is varied, a fringe is observed in the detector output. Iterating over source positions, the fringes’ complex visibilities allow the two-point detector response function to be retrieved: this correlation function corresponds to the state of coherence to which the detector is maximally sensitive. This detector response function can then be decomposed into a set of natural modes, in which the detector is incoherently sensitive to power. EAI therefore allows the reconstruction of the individual degrees of freedom through which the detector can absorb energy, including their relative sensitivities and full spatial forms. Coupling mechanisms into absorbing structures and their underlying solidstate phenomena can thus be studied, with direct applications in improving current infrared detector technology. EAI has previously been demonstrated for millimeter wavelength. Here, we outline the theoretical basis of EAI, and present a room-temperature 1550 nm wavelength infrared experiment we have constructed. Finally, we discuss how this experimental system will allow us to study optical coupling into fiber-based systems and near-infrared detectors.

Bayer filter arrays are commonly added to visible detectors to achieve multicolor sensitivity. To extend this approach to the infrared range, we present frequency selective surfaces that work in the mid-infrared range (MWIR). They are easily integrated in the device fabrication process and are based on a simple operating principle. They consist of a thin metallic sheet perforated with apertures filled with a high-index dielectric material. Each aperture behaves as a separate resonator. Its size determines the transmission wavelength λ. Using an original approach based on the temporal coupled mode theory, we show that metallic loss is negligible in the infrared range, as long as the filter bandwidth is large enough (typically <λ/10). We develop closed-form expressions for the radiative and dissipative loss rates and show that the transmission of the filter depends solely on their ratio. We present a prototype infrared detector functionalized with one such array of filters and characterize it by electro-optical measurements.

We propose a plasmo-thermomechanical mid-infrared detector operating at 4.3 μm wavelength. The design utilizes an array of the bimetallic fishbone nanowires that are suspended 50 nm above a 1.5 μm × 0.3 μm silicon nitride waveguide to create a leaky wave radiation. Moreover, the thermo-mechanically actuated nanowire will induce evanescent wave modulation that can be detected by the leaky wave or transmitted power of the waveguide. The antenna has a strip length of 1.77 μm and can yield an absorption coefficient of 42.4% with a period of 3.1 μm. Six unit cells are connected by a nanowire, and the fishbone-like nanowires are clamped at the two ends, leaving the center free to bend. The mid-infrared energy is absorbed by the resonant metallic antennas, resulting in a temperature increment. The mismatch of the thermal expansion coefficients of the bimetallic materials, gold and nickel, actuates the nanowire, and thus changes the gap between the nanowire and the waveguide. The deformation of the nanowire modulates the waveguide evanescent field, and hence alternates the transmitted power as well as the leak wave power. With a normal incident power of 4 μW/μm² , the temperature in the center of the nanobridge can be increased over 135 K above the ambient temperature, leading to an elevation of 23.5 nm in the center and thus weakening the evanescent modulation strength. The difference of S₂₁ caused by the gap change is 0.106. This methodology can be applied in other spectrums and the fabrication progress will be reported later.

HgTe and PbS colloidal quantum dots (CQD) with first excitonic absorption peak of about 2 μm and shorter (down to about 1 μm) have been synthesized and characterized. The synthesized CQDs were characterized using FTIR spectroscopy and TEM technique. The nanomaterials were tested for photo-electrical properties with photoconductive (PC) devices. The devices were fabricated by drop-casting a suspension of the CQDs on the fanout, followed by solid state ligand exchange (SSLE) process, and then spectral and electrical photoresponse of the device were measured. The SSLE process was evaluated thru absorption spectra of test samples. The device fabrication parameters were the number of deposited layers, the thickness of individual layers, the type of the substituting ligand, and the ligand exchange duration. For selected devices external quantum efficiency (EQE) was also determined.

The sun glint problem is a major issue to be addressed for MWIR marine targets detection. The traditional technique based on the single horizontal linear polarizer was a common method to reduce the sun glint by eliminating its s-polarized component, nevertheless, the residual p-polarized component could be still too strong to saturate the detector in some cases. To solve this problem, the improved polarization technique based on two rotatable polarizers is presented. The field experiment results show that the improved polarization technique can significantly reduce sun glint and enhance the contrast of target images, confirming the effectiveness of the technology.

Increasing requirements concerning the quality and lifetime of machine components in industrial and automotive applications require comprehensive investigations of the components in conditions close to the application. Irregularities in heating of mechanical parts reveal regions with increased loading of pressure, draft or friction. In the long run this leads to damage and total failure of the machine. Thermographic measurements of rotating objects, e.g., rolling bearings, brakes, and clutches provide an approach to investigate those defects. However, it is challenging to measure fast-rotating objects accurately. Currently one contact-free approach is performing stroboscopic measurements using an infrared sensor. The data acquisition is triggered so that the image is taken once per revolution. This leads to a huge loss of information on the majority of the movement and to motion blur. The objective of this research is showing the potential of using an optomechanical image derotator together with a thermographic camera. The derotator follows the rotation of the measurement object so that quasi-stationary thermal images during motion can be acquired by the infrared sensor. Unlike conventional derotators which use a glass prism to achieve this effect, the derotator within this work is equipped with a sophisticated reflector assembly. These reflectors are made of aluminum to transfer infrared radiation emitted by the rotating object. Because of the resulting stationary thermal image, the operation can be monitored continuously even for fast-rotating objects. The field of view can also be set to a small off-axis region of interest which then can be investigated with higher resolution or frame rate. To depict the potential of this approach, thermographic measurements on a rolling bearings in different operating states are presented.

An inverse analysis of experimentally measured infrared absorption spectra for the custom sorbent SiFA4H, nerve agent precursor and simulant DMMP, and intermolecularly bonded structure SiFA4H+DMMP is presented. These structures and their associated infrared spectra provide general understanding of the process whereby an analyte chemical may be detected using infrared spectral analysis. The inverse analysis presented provides estimates of permittivity functions, which when combined with the Clausius-Mossotti relation, can predict molecular polarizabilities associated with SiFA4H-SiFA4H and SiFA4H-DMMP interactions. Molecular polarizabilities deduced from measured absorption coefficients are modeled using molecular dynamics simulations.

In this paper, we report the performance of room temperature operated mid-infrared light emitting diode (LED) with an InSb buffer layer and AlInSb active/barrier layers, which showed to be suitable for non-dispersive infrared (NDIR) gas sensing. Characterization of the LED was performed and we found that good carrier confinement and crystalline quality was responsible for its high performance. High efficiency light extraction was obtained by adopting backside emission architecture together with surface roughening treatment and TiO₂ anti-reflection coating. The fabricated AlInSb LED showed 75% higher power conversion efficiency when compared with a commercially available device. The developed LED, together with a commercially available infrared (IR) detector equipped with band-pass optical filter (AK9710, manufactured by Asahi Kasei Microdevices) were coupled into a mirror system forming a light path length of 80 mm, which was tested for CO₂ gas sensing. For a non-absorbing environment, sensor output of 8 nA was obtained by driving the LED with peak current of 100 mA and, by exposing the system at CO₂ concentration of 1000 ppm signal reduction due to absorbance around 12% was obtained.

Infrared (IR) sensing technologies and systems operating from the near-infrared (NIR) to long-wave infrared (LWIR) spectra are being developed for a variety of defense and commercial systems applications. Reflection losses affecting a significant portion of the incident signal limits the performance of IR sensing systems. One of the critical technologies that will overcome this limitation and enhance the performance of IR sensing systems is the development of advanced antireflection (AR) coatings. Magnolia is actively involved in the development and advancement of ultrahigh performance AR coatings for a wide variety of defense and commercial applications. Ultrahigh performance nanostructured AR coatings have been demonstrated for UV to LWIR spectral bands using various substrates. The AR coatings enhance the optical transmission through optical components and devices by significantly minimizing reflection losses, a substantial improvement over conventional thin-film AR coating technologies. Nanostructured AR coatings are fabricated using a tunable self-assembly process on substrates that are transparent for a given spectrum of interest ranging from UV to LWIR. The nanostructured multilayer structures have been designed, developed and optimized for various optoelectronic applications. The optical properties of the AR-coated optical components and sensor substrates have been measured and fine-tuned to achieve a predicted high level of performance of the coatings. In this paper, we review our latest work on high quality nanostructure-based AR coatings, including recent efforts towards the development of nanostructured AR coatings on IR-transparent substrates.

An acousto-optic devices were designed and fabricated using high quality single crystals of mercurous halide (Hg₂X₂) that were grown by physical vapor transport method (PVT). The orientation and the crystalline quality of the grown crystals were determined using high resolution x-ray diffraction (HRXRD) technique. The full width at half maximum (FWHM) of the grown mercurous bromide (Hg₂Br₂) crystals was measured to be 0.13 degrees for (004) reflection, which is the best that has been achieved so far for PVT grown mercurous halide single crystals. The extended defects of the crystals were also analyzed using high resolution x-ray diffraction topography. Preliminary studies were carried out to evaluate the performance of the crystals on acousto-optic modulator (AOM) and acousto-optic tunable filter (AOTF) applications. The results indicate the grown mercurous halide crystals are excellent materials for acousto-optic modulator as well as acousto-optic tunable filter device fabrications. The diffraction efficiencies of the fabricated AOM device with 1152 and 1523nm wavelength lasers polarizing parallel to the acoustic wave were found to be 35% and 28%, respectively. The diffraction efficiencies of the fabricated AOTF device with 10600 nm wavelength laser found to be 26%.

This paper presents the effect of temperature on the natural frequency of (1,1) mode shape of a Resonant MEMS IR bolometer pixel in the range of 295-340 K. The detector pixel has a square plate geometry having side length of 1400μm and thickness of 35μm. The resonating plate is supported at its geometric center, enabling more robust pixels with fill factor greater than 90% and less complicated fabrication process. The sensor is fabricated using a Silicon-On-Glass (SOG) process. For the first time in the literature, the closed form equation to calculate the natural frequency of the fundamental mode shape of a MEMS square plate as a function of temperature change is derived for the single crystal silicon as the structural material. FEM simulations and experiments are conducted to verify the analytical model. For the electromechanical response characterization of the pixel structure, frequency response and system level temperature tests are conducted. Fundamental natural frequency shift is also tested during the frequency response tests for the same temperature range and the scale factor of the fabricated sensor is measured to be 1.90Hz/K for mode shape (1,1).

There has been great progress in recent years in advancing the state-of-the-art of Ga-free InAs/InAsSb superlattice (SL) materials for infrared detector applications, spurred by the observation of long minority carrier lifetimes in this material system. However, compositional and dimensional changes through antimony (Sb) segregation alter the detector properties from those originally designed. For this reason, in this work, the authors explore epitaxial conditions that can mitigate this segregation in order to produce high-quality SL materials for optimum detector performance. A nominal SL structure of 7.7 nm InAs/3.5 nm InAs_0.7 Sb_0.3 tailored for an approximately six-micron response at 5 K was used to optimize the epitaxial parameters. Since the growth of mixed AsSb alloys is complicated by the potential reaction of As with Sb surfaces, the authors vary the substrate temperature (T_s) in order to control the As surface reaction on a Sb surface. Experimental results indicate that the SL sample grown at the lowest investigated T_s produces the highest Sb-mole fraction x of ~0.3 in InAs1_-x Sb_x layers, which then decreases by 21 % as the T_s increases from 395 to 440 °C. This reduction causes an approximately 30 meV blueshift in the position of the excitonic photoluminescence (PL) peak. This finding differs from the results obtained from the Ga-containing InAs/GaSb SL equivalents, where the PL peak position remains constant at about 220 meV, regardless of T_s. The Ga-free SLs generally generate a broader PL linewidth than the corresponding Ga-containing SLs due to the higher spatial Sb distribution at the hetero-interfaces engendered by Sb segregation. In order for this newly proposed Ga-free SL materials to be viable for detector applications, the material problem associated with Sb segregation needs to be adequately controlled and further mitigated.

With the latest improvements of microbolometer focal plane arrays (FPA), uncooled infrared (IR) cameras are becoming the most widely used devices in thermography, especially in handheld devices. However the influences derived from changing ambient condition and the non-uniform response of the sensors make it more difficult to correct the nonuniformity of uncooled infrared camera. In this paper, based on the infrared radiation characteristic in the TEC-less uncooled infrared camera, a novel model was proposed for calibration-based non-uniformity correction (NUC). In this model, we introduce the FPA temperature, together with the responses of microbolometer under different ambient temperature to calculate the correction parameters. Based on the proposed model, we can work out the correction parameters with the calibration measurements under controlled ambient condition and uniform blackbody. All correction parameters can be determined after the calibration process and then be used to correct the non-uniformity of the infrared camera in real time. This paper presents the detail of the compensation procedure and the performance of the proposed calibration-based non-uniformity correction method. And our method was evaluated on realistic IR images obtained by a 384x288 pixels uncooled long wave infrared (LWIR) camera operated under changed ambient condition. The results show that our method can exclude the influence caused by the changed ambient condition, and ensure that the infrared camera has a stable performance.

To achieve negative-electron-affinity state, the atomically clean surface of GaAs-based photocathode is usually activated by cesium and oxygen in the ultrahigh vacuum environment. In view of the required computer-control of evaporation flow rates, the solid oxygen dispenser instead of gaseous oxygen is urgently needed just as the regular cesium dispenser. Accordingly, the solid cesium and oxygen dispensers were applied to activate epitaxial GaAs cathode samples. Two types of solid oxygen dispensers composed of barium peroxide powder and silver oxide powder respectively are employed to improve cathode photoemission performance. The experimental results show that the barium peroxidebased oxygen dispenser can release more oxygen and bring in higher activation photocurrent and spectral response than the silver oxide-based one. The unsatisfactory feature is that the silver oxide-based oxygen dispenser released effectual oxygen gas more slowly than the barium peroxide-based oxygen dispenser. Therefore, an effective activation technique was proposed to ameliorate this unfavorable phenomenon for the silver oxide-based dispenser, which can bring out the desired symmetry of photocurrent curve shape during the Cs/O alternate activation process. The improved activation technique would provide guidance for the optimization of activation craft.

We have designed and analysed a rib waveguide structure in recently reported Ga-Sb-S based highly nonlinear chalcogenide glass for nonlinear applications. The proposed waveguide structure possesses a very high nonlinear coefficient and can be used to generate broadband supercontinuum in mid-infrared domain. The reported design of the chalcogenide waveguide offers two zero dispersion values at 1800 nm and 2900 nm. Such rib waveguide structure is suitable to generate efficient supercontinuum generation ranging from 500 – 7400 μm. The reported waveguide can be used for the realization of the compact on-chip supercontinuum sources which are highly applicable in optical imaging, optical coherence tomography, food quality control, security and sensing.

An analysis of different cases of few-mode micro-optical fibers from 10 to 1 microns in diameter is performed based on solving the eigenvalue equation using both the weak guidance approximation (scalar LP modes) when the refractive index difference is small, and the exact full eigenvalue equation (vector TE, TM, HE and EH modes), when the refractive index difference is large, for example having air or a gas as the surrounding medium. One of the objectives of this analysis is to show at what point the propagation constant and optical field intensity of the fundamental modes LP₀₁ and HE₁₁ differ significantly depending of the refractive index difference, the other objective is to find out the evolution of the other modes along the final tapered section in a few mode fiber taper. The graphical behavior of the solutions of the eigenvalue equation is presented and the optical intensity distributions are calculated for different sizes, as for example in adiabatic tapers to evaluate the extent of the evanescent field. In general, the propagation constant and effective refractive index depends on the size of the core waveguide diameter, the refractive index difference and the wavelength. This analysis is useful to calculate the extension of the evanescent field in liquids or gases for optical fiber sensors that can be used to model, for example, fluorescent optical fiber sensors for biological or industrial applications. Additionally, the propagation characteristics of the few-mode micro optical fiber could be controlled or tuned by changing the refractive index of the surrounding media by changing, for example, its temperature.

This paper focuses on introducing the results of a model using a control system for an optical filter that can be tuned, using a solution that employs both, an elongation control system and a fiber Bragg grating. At the first stage, the optical characterization of the filter was made, then the stepper motors were chosen for the desired wavelength selection with a couple of pulleys which produce the grating elongation and, as a consequence, the wavelength shifting. The pulleys diameters were calculated to produce 0.8 nm shift for each filtering wavelength using a control program.