Self-assembled polymer photo-detectors (PPDs) composed of ruthenium complex N3 and PPDs based on thin films of poly(p-phenylene vinlyene) with sulfonated polystyrene are examined for their ability to function in a simulated space radiation environment. Examination of the PPD pre- and post- response data following gamma-ray irradiation ranging in total dose from 10 krad(Si) to 100 krad(Si) are examined. The output photovoltage was observed to decrease for all irradiated devices. The brief study was performed at room temperature and a discussion of the preliminary data and results are presented.

Spectral absorption behavior of Disperse Red-1 and Disperse Red-19 dyes incorporated into a series of polymers by covalent attachment, representing various chemical structures, is characterized by photothermal deflection spectroscopy. Of particular interest are the spectral characteristics of the red edge of the main dye electronic absorption peak, and the fine structure in the near-IR, dominated by overtones of fundamental C-H and O-H stretching modes. The spectral structure in these key regions can be influenced by inter- and intramolecular interactions, or conformational or configurational changes in the dye. The NIR structure, in turn, will dictate absorption loss in optical devices prepared from these materials at key transmission wavelengths (1.3 and 1.55 um) for waveguide devices. A well characterized dye-polymer system, DR1-PMMA, is compared with two other polymer systems. Differences in spectral absorption behavior is assessed in terms of polymer host structure and bonding environment.

The National Aeronautics and Space Administration's (NASA) Marshall Space Flight Center (MSFC) is concentrating research into the utilization of photonic materials for spacecraft propulsion. Spacecraft propulsion, using photonic materials, will be achieved using a solar sail. A sail operates on the principle that photons, originating from the sun, impart pressure and provide a source of spacecraft propulsion. The pressure can be increased, by a factor of two if the sun-facing surface is perfectly reflective. Solar sails are generally composed of a highly reflective metallic front layer, a thin polymeric substrate, and occasionally a highly emissive back surface. The Space Environmental Effects Team at MSFC is actively characterizing candidate solar sail materials to evaluate the thermo-optical and mechanical properties after exposure to a simulated Geosynchronous Transfer Orbit (GTO) radiation environment. This study is the first known characterization of solar sail materials exposed to space simulated environments. The technique of radiation dose verses material depth profiling was used to determine the orbital equivalent exposure doses. The solar sail exposure procedures and results of the material characterization will be discussed.

This paper will discuss some of the potential applications, opportunities, and challenges to the implementation of microwave photonics to future space-based platforms.

Normal incidence InAs/In_0.15Ga_0.85As dots-in-a-well detectors operating at T=78K with λ_cut-off ~8.2 μm and a spectral width (Δλ/λ) of 35% are reported. The peak at 7.2 μm is attributed to the bound-to-bound transitions between the ground state of the dot and the states within the InGaAs well. A broad shoulder around 5 μm, which is attributed to the bound to continuum transition, is also observed. Calibrated blackbody measurements at a device temperature of 78K yield a peak responsivity of 3.58 A/W (V_b=-1V), peak detectivity= 2.7x10⁹cmHz^1/2/W (V_b=-0.3V), conversion efficiency of 57% and a gain ~25.

A long-wavelength large format Quantum Well Infrared Photodetector (QWIP) focal plane array has been successfully used in a ground based astronomy experiment. QWIP arrays afford greater flexibility than the usual extrinsically doped semiconductor infrared (IR) arrays. Recently, we operated an infrared camera with a 256x256 QWIP array sensitive at 8.5 μm at the prime focus of the 5-m Hale telescope, obtaining the images. The remarkable noise stability - and low 1/f noise - of QWIP focal plane arrays enable camera to operate by modulating the optical signal with a nod period up to 100 s. A 500 s observation on dark sky renders a flat image with little indication of the low spatial frequency structures associated with imperfect sky substration or detector drifts. At low operating temperatures for low-background irradiance levels, high resistivity of thick barriers in the active region of QWIPs impeded electrons from entering the detector from the opposite electrode. This could lead to a delay in refilling the space-charge buildup, and result in a lower responsitivity at high optical modulation frequencies. In order to overcome this problem we have designed a new detector structure, the blocked intersubband detector (BID) with separate active quantum well region and blocking barrier.

Over just one decade since the chance discovery (or re-discovery) by Iijima, carbon nanotubes have attracted much interest from the science and technology communities, and have accumulated a vast array of claimed or likely applications. In the area of electronics, there is no shortage of remarkable and clever demonstrations of functional devices and logic gates. In the area of electro-optics, nanotubes have received much less attention but have perhaps as great potential. This article reviews some of our explorations on this new frontier of electro-optics, following a brief introduction of the basic nanotube properties, and summarizes the key findings of the electro-optic, and IR in particular, properties of nanotubes. It then highlights a few new and potentially promising directions in which future nanotube research could extended. The emphasis of this review paper will be on the basic physical principles underlying the experimental findings and device explorations, rather than on the device and structure specific data.

The peak responsivity of quantum-well infrared photodetectors (QWIPs) is known to decrease or "roll-off" to a lower plateau value as the frequency of an incoming time-varying photon irradiance increases. The time constant associated with the roll-off frequency depends on the amplitude of the applied DC bias, the incoming irradiance, and the device temperature. In this paper we demonstrate the scaling law for the responsivity roll-off and use it to estimate the quantum-well capacitance by first measuring the roll-off frequency as a function of bias and optical flux and then measuring the device dynamic resistance under similar conditions. The slope of the scatter plot of the roll-off angular frequency versus the inverse dynamic resistance is related to the quantum-well capacitance. Using this approach, we estimate the quantum-well capacitance in a fifty-well, Al_0.3Ga_0.7As/GaAs QWIP pixel of area 2.44 x 10^-4 cm^-2 to be ~ 1.22pF at 50 K.

In the presence of a time-dependent external source such as a bias electric field or an incident optical flux, electrons in quantum well and quantum dot devices experience non-adiabatic transport through the barrier layer between two adjacent quantum wells or quantum dots. This non-adiabatic transport process induces charge density fluctuations, resulting in several transient phenomena. When a time-dependent electric field is applied to the system, a dynamical breakdown (i.e., the dark current is dominated by a dielectric displacement current) of the quantum well or quantum dot photodetector is observed. If a chopped time-dependent optical flux is incident on either system, a dynamical drop in the photo-responsivity with increasing chopping frequency is also observed.

By layering quantum well stacks separated by partially transmissive linear gratings, similar to a multi-color QWIP, one may be able to detect the full Stokes vector at a single pixel. Such a detector would greatly aid polarization-based automated algorithms to detect targets from earth-gazing platforms. We report results from a theoretical calculation of normally incident infrared light absorbed by quantum wells in an eight-layer quantum-well/grating structure. The structure consists of four quantum-well stacks, of 50 quantum wells each, separated by contact layers and lamellar gratings. The gratings following the first three quantum well stacks are formed by perfectly conducting rectangular strips separated by a transparent dielectric that allows some light to be transmitted. The top grating, following the fourth quantum well stack, is completely reflective. Each of the four lamellar gratings is oriented at a different angle. Incident radiation is diffracted and reflected to different orders and at different angles at each of the four gratings. The model is based on a uniaxial-optics transfer-matrix technique. We calculate the energy absorbed by each of the layers. This in turn allows one to predict and compare which layers will respond for partially- and fully-polarized incident light of either linear or circular polarization.

Optoelectronic devices based on nonlinear optic (NLO) polymers, with electro-optic (EO) coefficients in excess of 100 pm/V at 1.06 μm and dielectric constants of < 3, have demonstrated 100+ GHz data rates with less than 4 volt operating voltages. This has gained interest from the space based applications community, since in addition to being tolerant to a space environment, electro-optic devices for space applications will also need to operate at high data rates and at low operational powers. We have investigated various NLO polymers for core materials as well as passive polymers with various conductivities, both ionic and electronic, suitable for use as optical cladding layers in NLO polymer based opto-electronic devices. Our goal was to find materials that would be tolerant to irradiation as well as maximizing the nonlinearity of the NLO core material, thus minimizing the total applied poling voltage, and minimize the optical absorption loss. Using a cladding material that is more conductive than the NLO core material, the majority of the applied poling voltage is dropped across the core, thus maximizing the EO coefficient with minimum applied voltage or power. We found, however, that it is necessary to balance the optical and electromagnetic properties of the materials with their processability and compatibility.

The Fluid Science Laboratory (FSL) to be embarked on board the European Space Agency's Columbus Orbital Facility (COF) as part of the International Space Station (ISS) is a multi-user facility for the performance of microgravity research. It comprises a very complex optical bench, which can be configured in a number of different ways depending on the experiments to be undertaken. In particular several different types of interferometry including Phase-Shift, Electronic Speckle Pattern and Wollaston Shearing are feasible. This provides FSL and the scientists who use it with highly sensitive optical diagnostic tools for fluid physics research under microgravity conditions over extended periods of time. FSL is foreseen to operate on orbit for ten years. In this regard the entire optical bench and its optical components must withstand the launch, microgravity, thermal and radiation environments without significant degradation in performance over that time. The total radiation qualification dose for FSL is relatively low in absolute terms at a value 1400 Rad (14 Gy). It was expected that this would not cause a problem, but prior to these tests there was no quantitative data at all available on the radiation response of most of the optical glasses used, and hence a formal statement of qualification could not be made. This paper presents results of the radiation testing of most of the important glass materials used on the optical bench. The data are presented and analyzed in a parametric way such that the information may be applied to other optical instruments operating in a similar space radiation environment and for intermediate or longer timescales than the nominal FSL end of life of ten years.

Radiation sensitivity of glass is a general concern for the designer of Space optical instruments. ASTRIUM, in cooperation with SCK-CEN, has conducted a study (under ESA sponsorship) to define the approach for the gathering of a comprehensive database to quantify these effects through the use of linear sensitivity coefficients (called "Dose Coefficients"). These "Dose coefficients" cover not only transmittance but also other characteristics such as refractive index. After having recalled the basics of the proposed approach, results of the first irradiation tests which have been run on a selected set of classical glasses nd their Radiation hardened Cerium doped analogs (including BK7, K5, LaK9 and other Schott glasses) will be discussed. PRotons and gamma radiation have been performed with the aim to demonstrate equivalence, thus allowing to further considering only gamma radiation for an extensive testing of available glasses. Relaxation impacts on some months period have been tentatively analyzed. All these measurements have been processed and the modeling approach of the radiations impacts has been derived, as shown in the publication from A. Gusarov at this conference. This will constitute the grounds for the building of a comprehensive "Dose Coefficients" data base, as expressed in the publication from D. Doyle also at this conference. From this, recommendations for a sound characterization of radiation impacts on refractive optical materials have been established and are the subject of this publication.

We analyze the applicability of a number of exponent-type phenomenological kinetics for transmission degradation prediction in commercial optical glasses during and after irradiation. The analysis is based on post-radiation transmission measurements over a 5 years time interval of a commercial boro-silicate glass (BK7, Schott). A conclusion is drawn that the choice should be made between the stretched-exponential and the multi-exponential functions. We apply those kinetics to simulate kinetics of BK7 glass transmission spectra subject to Co⁶⁰ gamma-radiation in the framework of the previously developed phenomenological model. Calculated transmission spectra agree well with our experimental data.

The number of defensive and reconnaissance systems requiring infrared focal plane arrays (IRFPAs) has steadily increased over the last few years. These missions require operation of the IRFPAs through nuclear environments both manmade and natural. The Mission Research Corporation Longmire Laboratory was formed to support electro-optic testing of these IRFPAs and other devices such as visible CCDs and FPAs, and IR and visible optical components. Early on, it was found that it would be desirable to possess a real-time analysis capability for all test data collected in the laboratory. Without a real-time, or near real-time analysis capability, a significant amount of resources can be lost collecting large quantities of erroneous data. A real-time capability has yet to be achieved, but a near real-time capability, TDAT (Test Data Analysis Tool) has been developed and has been in use at Longmire Laboratory for the past year. TDAT has been developed entirely in-house in the Borland Delphi programming language. This allows for rapid modifications to the code's capabilities when needed by laboratory users.

A summary is presented of the combined effects of radiation damage, accelerated annealing and accelerated ageing in 1310nm InGaAsP/InP multi-quantum-well lasers, the type chosen for use in the CMS Tracker optical links. The radiation damage effects are compared for a variety of radiation sources: ⁶⁰Co-gamma, 0.8MeV (average energy) neutrons, 20MeV (average energy) neutrons and 300MeV/c pions that represent important parts of the spectrum of particles that will be encountered in the CMS Tracker. The relative damage factors of the various sources are calculated by comparing the laser threshold current increase due to radiation damage giving ~0 : 0.12 : 0.53 : 1 for ⁶⁰Co-gamma, ~0.8MeV neutrons, ~20MeV neutrons with respect to 300MeV/c pions. The effects of bias current and temperature on the annealing were measured and, in all cases, the annealing is proportional to log(annealing time). A bias current of 60mA increases the annealing, in terms of the time taken to anneal a given amount, by a factor of 10 relative to 0mA. The annealing rate is also accelerated by heating the irradiated lasers and recovery occurs ~10 times faster at 60°C than at 20°C. The long-term ageing properties of irradiated lasers were also measured in an accelerated test carried out at 80°C, for 2500 hours, at a bias current of 60mA. No wearout-related degradation was observed in any of the devices. The combined results of these studies have been used to estimate the long-term damage expected for this type of laser operating inside the CMS Tracker. In the worst case of a laser operating at a distance of 22cm from the beam-axis in the forward region of the Tracker, the maximum threshold increase will be ~6mA over the first 10 years of LHC running.

In this paper we describe a new approach to the manufacture of Si based optical emitters. Dislocation engineering, using entirely ULSI compatible technology has been shown to be a viable route to the production of efficient LED's operating at room temperature. External quantum efficiencies of ~ 10^-4 have been realised for un-packaged devices operating at room temperature. This approach has also been shown to yield great benefits in the control of thermal quenching for other material systems, such as the FeSi₂, where room temperature operational devices based at 1.5um have been demonstrated

Optical fiber technology is seriously considered for communication and monitoring applications during the operation and maintenance of future thermonuclear fusion reactors. Their environment is characterized, in particular, by possibly high gamma dose-rates and total doses in excess of 10 MGy. In addition, the maintenance equipment might be stored in close vicinity of the reactor during its operation and therefore the communication devices might also be exposed to a substantial neutron fluence. The feasibility of applying photonic technology in these radiation fields therefore needs to be assessed. Whereas many reports deal with the radiation behavior of a variety of fiber-optic devices, only little information is available on the radiation tolerance at high total dose (e.g. > 1 MGy). We describe our recent results obtained on vertical-cavity surface-emitting laser (VCSEL) assemblies. We have conducted high total dose (up to 20 MGy) irradiation experiments on such devices, which confirmed their excellent gamma radiation hardness. The optical power loss at nominal forward current was less than 2 dB and the threshold current remained unaltered. We have also irradiated these devices with neutrons inside the BR1 reactor (SCK•CEN, Mol, Belgium) up to a total fluence on the order of 10¹⁵ n∙cm^-2. The response of VCSELs to neutrons is, as expected, different from that to gamma radiation. VCSELs previously exposed to gamma rays exhibited an accelerated degradation under neutron radiation compared to not pre-irradiated devices. The beneficial effect of applying a continuous forward bias to the VCSELs is also evidenced.

In this article we formulate the problem of modeling the distribution of gamma noise in detectors. We exactly solve for the gamma noise distribution in the important special case of an exponential pulse height distribution. More generally, we also present and prove the relationship between the moments of the gamma noise distribution and the underlying pulse height distribution. A simple method is presented for computing the unknown parameters of the pulse height distribution given gamma noise data at varying event rates.

This paper deals with the issues to accept, launch, and operate a bilateral space project with the Russians, exemplary shown with the Modular Optoelectronic Multispectral / Stereo Scanner (MOMS) on the Priroda module of the MIR space station. Emphasis will be given not only to ground aspects on requirements, PA & Safety and Crew training, but also to space operations concerning special space environment and crew activities. Exemplary some space environmental conditions will be presented inside and outside the Priroda module as well as mechanical and acoustic loads, general climatic conditions, and inflight maintenance and repair requirements. Also the helpfulness of the Russian side will be underlined. This paper is therefore also an attempt to improve the co-operation of the other nations with the Russians on the International Space Station (ISS).

With the rapidly increasing insertion of photonic devices, circuits and subsystems into NASA spacecraft, a variety of issues associated with reliability and radiation tolerance have arisen. In this paper, we discuss these issues from the perspective of the work currently ongoing in the NASA Electronic Parts and Packaging (NEPP) Program. This Program is focused on evaluating the reliability and radiation response of advanced and emerging microelectronics and photonics technologies of interest to NASA spacecraft system designers. Examples to be discussed include radiation studies of various optoelectronic devices and reliability of photonic components. These studies have been motivated in part by problems observed in space that include the failure of optocouplers on TOPEX/Poseidon, and the observation of single event-induced transients in the Hubble Space Telescope.

The implementation of Wavelength Division Multiplexing (WDM) techniques in fiber optic data-communication links for nuclear installations requires to assess the radiation tolerance of passive WDM multiplexers. Nowadays, Fibre Bragg gratings (FBG) have become a key component in all-fibre WDM multiplexers. Up to now, only accelerated short term irradiation experiments of FBG filters have been discussed, suggesting possible ways to optimise their radiation tolerance. In this paper, we evaluate the long-term behaviour of FBGs filters, written in different types of optical fibres, after two years of continuous low-dose rate gamma-neutron irradiation. We compare these results with our previous accelerated tests. We evidence that FBG filters can withstand years in a nuclear environment, while keeping their filtering properties at an acceptable level.

Optical fibers stimulate much interest since many years for their potential use in various nuclear environments, both for radiation tolerant and EMI-free data communication as well as for distributed sensing. Besides monitoring temperature and stress, measuring ionizing doses with optical fibers is particularly essential in applications such as long-term nuclear waste disposal monitoring, and for real-time aging monitoring of power and signal cables installed inside a reactor containment building. Two distinct options exist to perform optical fiber dosimetry. First, find an accurate model for a restricted application field that accounts for all the parameters that influence the radiation response of a standard fiber, or second, develop a dedicated fiber with a response that will solely depend on the deposited energy. Using various models presented in literature, we evaluate both standard commercially available and custom-made optical fibers under gamma radiation, particularly for distributed dosimetry applications with an optical time domain reflectometer (OTDR). We therefore present the radiation induced attenuation at near-infrared telecom wavelengths up to MGy total dose levels, with dose rates ranging from about 1 Gy/h up to 1 kGy/h, whereas temperature was raised step-wise from 25 °C to 85 °C. Our results allow to determine and compare the practical limitations of distributed dose measurements with both fiber types in terms of temperature sensitivity, dose estimation accuracy and spatial resolution.

This paper describes the development of a 750x750 pixels CMOS image sensor for star tracker applications. A first demonstrator of such a star tracker called SSM star tracker built around a 512x512 detector has been recently developed and proves the feasibility of such instrument. In order to take fully advantage of the CMOS image sensor step, the 750x750 device called SSM CMOS detector which will take part of the final star tracker, can be considered as a major technical breakthrough that gives a decisive advantage in terms of on satellite implementation cost and flexibility (sensor mass and power consumption minimisation, electronics and architecture flexibility). Indeed, built using the 0.5μm Alcatel Microelectronics standard CMOS technolgoy, the SSM CMOS detector will feature on-chip temperature sensor and on-chip sequencer. In order to evaluate the radiation tolerance of such manufacturing technology, a radiation campaign that contains studies of total dose and latch-up effects has been led on a specific test vehicle.

The Large Hadron Collider (LHC), currently under construction at CERN, Geneva, will collide proton beams of energy 7 TeV. The high luminosity of the machine will lead to a severe radiation environment for detectors such as ATLAS. The ATLAS Semiconductor Tracker (SCT) must be able to tolerate a radiation field equivalent to an ionising dose of 10 Mrad (Si) and a neutron fluence of 2x10¹⁴cm^-2 (1MeV,Si) over the 10 year lifetime of the experiment. The SCT is instrumented by silicon microstrip detectors and their front-end chips (ABCDs). Data is transferred from, and control signals to, the ABCDs using multimode optical links carrying light at 840 nm. The incoming timing, trigger and control (TTC) link uses biphase mark encoding to send 40 Mbit/s control signals along with a 40 MHz clock down a single fibre. Optical signals are received by a p-i-n diode and decoded by DORIC chips. Data in electrical form from the ABCDs is used to moderate two VCSELs by means of a VCSEL driver chip (VDC). Each detector module carries 12 ABCDs and is served by two optical fibres for data readout and one for TTC signals. There are 4088 such modules within the SCT. The system performance specifications and architecture are described, followed by test results on individual components and complete links. The optical fibre, active optical components, chips, packaging and interconnects have all been qualified to the necessary radiation levels. This has involved studies of total dose effects, single event upset and ageing at elevated temperatures and details of these studies are presented.

Proton induced charge transfer efficiency (CTE) degradation has been studied in the large format charge-coupled device (CCD) flight-like candidates for Wide Field Camera 3 for the Hubble Space Telescope. These detectors were irradiated with different proton fluences. This paper focuses on the statistical nature of CTE degradation due to damage on one of the irradiated devices with exceptional initial CTE characteristics. In radiation damaged CCDs, CTE noise can be the dominant noise component. In contrast to other noise sources, CTE noise has a component of fixed pattern noise that can be removed by the appropriate calibration technique. A large set of data was acquired and analysis of it confirms the expectation that CTE damage is a local phenomenon and it varies widely across the CCD surface. Possible mitigation solutions and their practicality are discussed in some detail.

The practical boundaries surrounding the design of very high resolution image sensors have been studied. The case study used to analyze these practical boundaries is a CMOS photodiode active pixel sensor (APS) image sensor with pixel array format of 3,072 (H) X 2,048 (V). The frame rate of the image sensor is variable up to 30 frames per second (fps), leading to a maximum image data throughput of 180 M pixels per second. The pixel size is 6.0 μm, resulting in a pixel fill factor of approximately 48% (implemented in a 0.25 μm CMOS fabrication process) and a 4/3 inch optical format. The resultant die fill factor is approximately 54%. The column-parallel approach, which works well for both the on-chip analog signal processing and analog-to-digital conversion, is adopted. The 10-bit successive approximation ADC was deemed suitable for on-chip integration. The projected total power consumption of the case study image sensor chip is below 200 mW at 3.3-V power supply and below 100 mW at 1.5-V power supply. These power estimates were made for operation at full resolution (6 M pixels per frame) and at maximum frame rate (30 fps), leading to a maximum digital image data throughput of 1.8 G bits per second.