Mid-IR spectrometers with adequate resolution for chemical sensing and identification are typically large, heavy, and require sophisticated non-stationary optical components. Such spectrometers are limited to laboratory settings. We propose an alternative based on semiconductor micro-fabrication techniques. The device consists of several enabling parts: a compact broad-band IR source, photonic waveguides, a photon-to-surface-plasmon transformer, a surfaceplasmon sample-interaction region, and an array of silicon ring-resonators and detectors to analyze the spectrum. Design considerations and lessons learned from initial experiments are presented.

High aspect ratio features in mercury cadmium telluride (MCT) for advanced IR sensor technologies present a challenge to deposition of electrical passivation materials. Deposition of aluminum oxide (Al2O3) onto MCT near room temperature by plasma assisted atomic layer deposition was studied. Conformal deposition was studied through SEM images of thick (ca. 150 nm) deposition onto high aspect ratio features dry etched into MCT. Minority carrier lifetime was measured by photoconductive decay transients of MCT before and after deposition, and the lifetimes compared.

This study proposes a solution for an excessive dark current by a sharing capacitor, which avoids output signal distortion due to integration voltage saturation. Integration capacitance can be changed by adding a switch in the pixel circuit, which will increase the capacitance by two times the original. This circuit also provides output functions of either single-band or dual-band by switching to different sensor. This integrated readout circuit design adopts the TSMC 0.35um 2P4M CMOS 5V process, run on a 5V power supply and operated at a 3MHz clock rate. The dual-band pixel circuit uses an interlace structure, the pixel circuit areas of the two wavelengths are both 30um x 30um. The mid-wave and long-wave sensor currents are from 1nA to 2nA and 6nA to 8nA, respectively, and output swing is 2.8V.

Imaging in visible light at room temperature is now a well-mastered technology, whereas imaging in the near infrared (NIR) remains a challenge. NIR imaging has many applications like sensing, night vision and biological diagnostics. Unfortunately, silicon detectors are inefficient above 1000 nm, and other IR technologies still need low working temperatures and are thus expensive. Colloidal quantum dots can overcome these limitations thanks to their absorption wavelength tunability depending on their chemical composition and size. After a brief review of this research field, we will present the preparation of hybrid photodetectors using NIR absorbing PbS quantum dots in combination with poly(3-hexylthiopene) and PCBM. We discuss different solution based deposition processes for device fabrication (spincoating, dip-coating, doctor blading, inkjet printing). Preliminary device tests result in a detectivity of 4.7.10⁹ Jones at 1300 nm.

Long-wave infrared (LWIR) detector technologies with the ability to operate at or near room temperature are very important for many civil and military applications including chemical identification, surveillance, defense and medical diagnostics. Eliminating the need for cryogenics in a detector system can reduce cost, weight and power consumption; simplify the detection system design and allow for widespread usage. In recent years, infrared (IR) detectors based on uni-polar barrier designs have gained interest for their ability to lower dark current and increase a detector's operating temperature. Our group is currently investigating nBn and pBp detectors with InAs/GaSb strain layer superlattice (SLS) absorbers (n) and contacts (n), and AlGaSb and InAs/AlSb superlattice electron and hole barriers (B) respectively. For the case of the nBn structure, the wide-band-gap barrier material (AlGaSb) exhibits a large conduction band offset and a small valence band offset with the narrow-band-gap absorber material. For the pBp structure (InAs/AlSb superlattice barrier), the converse is true with a large valence band offset between the barrier and absorber and a small or zero conduction band offset. Like the built-in barrier in a p-n junction, the heterojunction barrier blocks the majority carriers allowing free movement of photogenerated minority carriers. However, the barrier in an nBn or pBp detector, in contrast with a p-n junction depletion layer, does not contribute to generation-recombination (G-R) current. In this report we aim to investigate and contrast the performance characteristics of an SLS nBn detector with that of and SLS pBp detector.

Diminished performance due to poor chemical and electrical surface stability of InAs/GaSb SL photodetectors continues to be a major hurdle to the realization of the theoretically predicted high performance of this material system. Improved epitaxial growth conditions have yielded improvements in material quality over the past several years. However, surface instability resulting in electrical shunt pathways across the junction, and diminished device performance over time is still a major limiting factor for application of InAs/GaSb SL in long-wavelength infrared detectors. This study focuses on a two-step approach towards the successful surface passivation of long-wavelength InAs/GaSb superlattice structures. Two distinct sulfide chemical surface treatments were applied to inhibit the formation of native surface oxides and satisfy dangling bonds. This was followed by the application of a robust SU8-2 dielectric treatment on the mesa sidewalls to inhibit sulfide layer degradation and oxidation of the surface over time. A variable area diode analysis (VADA) technique employing diodes of variable diameter (40-400um) enabled the investigation of surface resistivity as a result of different passivation treatments. Temperature dependent studies of the dark current were used to understand the dominating current mechanisms.

High resolution imaging in the UV band has a lot of applications in Defense and Commercial Applications. The shortest wavelength is desired for spatial resolution which allows for small pixels and large formats. UVAPD's have been demonstrated as discrete devices demonstrating gain. The next frontier is to develop UV APD arrays with high gain to demonstrate high resolution imaging. We also disuses our recent efforts on development of APD's using MOCVD of GaN/ AlGaN. We present an analytical model that can predict sensor performance in the UV band using p-i-n or APD detectors with and without gain and other detector and sensor parameters for a desired UV band of interest. SNR's can be modeled from illuminated targets at various distances with high resolution under standard MODTRAN atmospheres in the UV band using detector arrays with unity gain and with high gain APD along with continuous or pulsed UV lasers.

The requirements for advanced EO/IR sensor technologies are discussed in the context of evolving military operations, with significant emphasis on the development of new sensing technologies to meet the challenges posed by asymmetric threats. The Electro-Magnetic Remote Sensing (EMRS DTC) was established in 2003 to provide a centre of excellence in sensor research and development, supporting new capabilities in key military areas such as precision attack, battlespace manoeuvre and information superiority. In the area of advanced electro-optic technology, the DTC has supported work on discriminative imaging, advanced detectors, laser components/technologies, and novel optical techniques. This paper provides a summary of some of the EO/IR technologies explored by the DTC.

In a previous paper,¹ we described a method for significantly reducing the read noise of HAWAII-2RG (H2RG) and SIDECAR application specific integrated circuit (ASIC) based detector systems by making better use of reference signals. "Improved Reference Sampling & Subtraction" (IRS²; pronounced "IRS-square") is based on: (1) making better use of the H2RG's reference output, (2) sampling reference pixels more frequently in the time domain, and (3) optimal subtraction of both the reference output and reference pixels in the Fourier domain. Here we demonstrate that IRS² works as expected using an engineering grade James Webb Space Telescope (JWST) SIDECAR ASIC and H2RG detector array. We were able to reduce the read noise per frame from 25 e- rms using traditional JWST readout to 10 e- rms per frame using IRS². The only aspect of the system that we changed to make these impressive improvements was the SIDECAR ASIC readout software -we did not change the hardware.

Mission concepts for NASA's Wide Field Infrared Survey Telescope (WFIRST)^1,2, ESA's Euclid^3,4 mission, as well as next-generation ground-based surveys require large mosaic focal planes sensitive in both visible and near infrared (NIR) wavelengths. We have developed space-qualified detectors, readout electronics and focal plane design techniques that can be used to intermingle CCDs and NIR detectors on a single, silicon carbide (SiC) cold plate. This enables optimized, wideband observing strategies. The CCDs, developed at Lawrence Berkeley National Laboratory, are fully-depleted, pchannel devices that are backside illuminated and capable of operating at temperatures down to 120K. The NIR detectors are 1.7 μm and 2.0 μm wavelength cutoff H2RG® HgCdTe, manufactured by Teledyne Imaging Sensors under contract to LBNL. Both the CCDs and NIR detectors are packaged on 4-side abuttable SiC pedestals with a common mounting footprint supporting a 44 mm mosaic pitch. Both types of detectors have direct-attached readout electronics that convert the detector signal directly to serial, digital data streams and allow a flexible, low cost data acquisition strategy to enable large data rates. A mosaic of these detectors can be operated at a common temperature that achieves the required dark current and read noise performance necessary for dark energy observations. We report here the qualification testing and performance verification for a focal plane that accommodates a 4x8 array of CCDs and HgCdTe detectors.

A Custom made NIR spectroscope was used to determine the moisture content of in-shell peanuts of two different market type peanuts namely Virginia and Valencia. Peanuts were conditioned to different moisture levels between 6 and 26 % (wet basis). Samples from the different moisture levels were separated into two groups one for calibration and the other for validation. NIR absorption spectral data from 1000 nm to 2500 nm were collected on the peanuts from the calibration and validation groups. Measurements were obtained on 30 replicates within each moisture level. Reference moisture data were developed using standard air-oven method on calibration set samples. Partial Least Square (PLS) analysis was performed on the calibration set with certain pretreatments on the measured data and models were developed using the reference moisture data. The Standard Error of Calibration (SEC) and R² of the calibration models were computed to select the best calibration model for each of the two peanut types. Both Valencia and Virginia types gave R² of 0.99 for the pretreated as well as for the raw spectral data. The selected models were used to predict the moisture content of peanuts in the validation sample set. Predicted moisture contents of the validation samples were compared with their air-oven moisture values determined similarly as for the calibration samples. Goodness of fit was determined based on the lowest Standard Error of Prediction (SEP) and highest R² value obtained for the prediction models. The model, with reflectance plus normalization spectral data with an SEP of 0.74 for Valencia and 1.57 for Virginia type in-shell peanuts was selected as the best model. The corresponding R2 values were 0.98 for both peanut types.

This paper reviews the work of several teams at ARL. In the first section a summary of the work done by the photovoltaic devices team is presented, the team is using quantum dots to enhance the efficiency of solar photovoltaic devices. We have discovered that doping the quantum dots is critical in enhancing the efficiency of the solar cells. In the quantum well arena we are developing type II SLS detector material for high performance focal plane array applications, so far we have observed that the minority carrier lifetimes have been short. This presents a major barrier towards the realization of high performance focal plane arrays. This paper discusses some of the details of type II SLS material studies as they pertain to minority carrier lifetime studies.

The Corrugated Quantum Well Infrared Photodetector (C-QWIP) holds significant performance and other advantages over other infrared (IR) detectors. However, one disadvantage of the detector is the relatively low operating temperature needed to suppress the dark current. By coating two additional layers (thin insulator and high critical temperature (Tc) superconductor) on the top contact layer of a C-QWIP wafer, the top three layers of the detector form a high-Tc superconducting single electron tunneling junction. It could act as an electron filter because of the presence of an energy gap in superconductors. For QWIPs, the photo electrons and dark electrons are well separated in energy, most dark current is conducting below the quantum well (QW) barrier height and most photo current is conducting above the barrier height. Most dark electrons thus could be blocked by the junction while most photo electrons pass the junction by applying an appropriate voltage. Therefore, both the sensitivity and the operating temperature of the detector could be improved. Our calculation shows that the filter could provide 40% or 70% improvement in Noise Equivalent Temperature Difference (NETD) of detector focal plane arrays (FPAs) at normal operating temperature, depending on whether the detector emitter photocurrent to dark current ratio is = 1 (Emitter is background limited BLIP) or = 0.1 (Emitter is far from BLIP). For both cases, the filter could increase the detector FPAs operating temperatures up to 90K (30K improvement) with 15% to 25% NETD improvement respectively.

The multiplicative and additive components of the fixed-pattern noise (FPN) in infrared (IR) focal plane arrays (FPAs) are typically modeled as time-stationary, spatially unstructured random processes. Even though the latter assumption is convenient, it is also inaccurate due to FPN is indeed observed as a spatial pattern, with random intensity values, superimposed over the true images. In this paper, the spatial structure in both the multiplicative and the additive components of the FPN has been modeled in the frequency domain. The key observation in the proposed models is that regular spatial patterns manifest themselves as narrowband components in the magnitude spectrum of an image. Thus, the spatial structure of FPN can be abstracted in a straightforward manner by approximating the spectral response of the FPN. Moreover, the random intensity of the FPN has been also modeled by matching the empirically estimated distributions of the intensity values of both multiplicative and additive components of the FPN. Experimental characterization of FPN has been conducted using black-body radiator sources, and the theoretical as well as practical applicability of the proposed models has been illustrated by both synthesizing FPN from three different IR cameras and by proposing a simple yet effective metric to assess the amount of FPN in FPA-based cameras.

Algorithms for striping noise compensation (SNC) for push-broom hyperspectral cameras (PBHCs) are primarily based on image processing techniques. These algorithms rely on the spatial and temporal information available at the readout data; however, they disregard the large amount of spectral information also available at the data. In this paper such flaw has been tackled and a multidimensional approach for SNC is proposed. The main assumption of the proposed approach is the short-term stationary behavior of the spatial, spectral, and temporal input information. This assumption is justified after analyzing the optoelectronic sampling mechanism carried out by PBHCs. Namely, when the wavelength-resolution of hyperspectral cameras is high enough with respect to the target application, the spectral information at neighboring photodetectors in adjacent spectral bands can be regarded as a stationary input. Moreover, when the temporal scanning of hyperspectral information is fast enough, consecutive temporal and spectral data samples can also be regarded as a stationary input at a single photodetector. The strength and applicability of the multidimensional approach presented here is illustrated by compensating for stripping noise real hyperspectral images. To this end, a laboratory prototype, based on a Photonfocus Hurricane hyperspectral camera, has been implemented to acquire data in the range of 400-1000 [nm], at a wavelength resolution of 1.04 [nm]. A mobile platform has been also constructed to simulate and synchronize the scanning procedure of the camera. Finally, an image-processing-based SNC algorithm has been extended yielding an approach that employs all the multidimensional information collected by the camera.

The performance of leading HgCdTe p-n junction infrared (IR) device technology is limited by thermal generationrecombination (G-R) mechanisms and material processing challenges associated with achieving low, controllable in-situ p-type doping using molecular beam epitaxy (MBE) growth techniques. These aspects are addressed in the proposed hybrid HgCdTe NBνN structure which relies on band gap engineered layers to suppress Shockley-Read-Hall (SRH) and Auger G-R processes contributing to performance degradation. The unipolar NBνN architecture provides the desired advantages of a simplified fabrication process, eliminating p-type doping requirements. Physics-based numerical device simulations incorporating established HgCdTe material parameters and G-R mechanisms are used to study the performance characteristics of a long wavelength infrared (LWIR) NBνN device with a 12 μm cut-off wavelength. The calculated results are compared to those values obtained for an LWIR HgCdTe nBn device. Theoretical dark current density (J_dark) values of the NBνN device are lower by an order of magnitude or more for temperatures between 50 K and 245 K. Calculated detectivity (D*) values of 2.367 x 10¹⁴ - 2.273 x 1011 cm Hz^0.5/W for temperatures ranging from 50 K and 95 K, respectively, are observed in the NBνN structure.

The micro-channel plate (MCP) is an important part to imaging quality of image intensifier. In order to obtained high quality of optoelectronic image devices, the microchannel plate (MCP) should be evaluated before assembled in the devices. A new method for noise power factor determination of MCP is described in this paper. The measurements are in accordance with theory and experiments reported. The system consists of vacuum chamber, electron gun, high voltage supply, imaging luminance meter, control units, signal processing circuit, A/D converter, D/A converter, communication unit, industrial computer and measurement software.

Time-resolved photoluminescence measurements are used to study minority carrier lifetimes in type II superlattices (T2- SL) to investigate the recombination mechanisms that currently limit their performance. Time-domain measurements of the photoluminescence signal demonstrate multiple exponential decay, which provide information on background carriers, acceptor states and trap states. The temperature dependence of the TRPL signal shows that the carrier lifetime is dominated by Shockley-Read-Hall recombination. Optimal sample design for photoluminescence measurements is discussed. Photoluminescence measurements and modeling of the time-resolved signal in device structures demonstrate that the restoring current in a narrow bandgap junction dominates the carrier recombination, leading to measured lifetimes that are ostensibly long. Experimental results are presented on T2-SL samples that vary the superlattice absorber width and doping level. The effect of the interface type on carrier lifetime is investigated in multiple quantum well structures. Variations of the absorber width, doping level and interface type are not found to strongly influence the carrier lifetime.

In this paper, the relation between the photoluminescence (PL) intensity and the PL peak wavelength was studied. A linear decrease of the PL intensity with increasing cut-off wavelength of long wavelength infrared CBIRDs was observed at 77 K and the trend remained unchanged in the temperature range 10 - 77 K. This relation between the PL intensity and the peak wavelength can be favorably used for comparison of the optical quality of samples with different PL peak wavelengths. A strong increase of the width of the PL spectrum in the studied temperature interval was observed, which was attributed to thermal broadening.

We describe a non-contact optical measurement method used to determine the surface flatness of a cryogenic sensor array developed for the JDEM mission. Large focal planes envisioned for future visible to near infra-red astronomical large area point-source surveys such as JDEM, WFIRST, or EUCLID must operate at cryogenic temperatures while maintaining focal plane flatness within a few 10's of μm over half-meter scales. These constraints are imposed by sensitivity conditions that demand low noise observations from the sensors and the large-field, fast optical telescopes necessary to obtain the science yield. Verifying cryogenic focal plane flatness is challenging because μm level excursions need to be measured within and across many multi-cm sized sensors using no physical contact and while situated within a high-vacuum chamber. We have used an optical metrology Shack-Hartmann scheme to measure the 36x18 cm focal plane developed for the JDEM mission at the Lawrence Berkeley National Laboratory. The focal plane holds a 4x8 array of CCDs and HgCdTe detectors. The flatness measurement scheme uses a telescope-fed micro-lens array that samples the focal plane to determine slope changes of individual sensor zones.

In this work we investigate the influence of extractor design and temperature on transport properties of quantum cascade detector. For this purpose we realize numerical calculation of electron lifetimes considering electronphonon and electron impurities scattering. Electron-phonon interactions are treated using Fermi Golden Rule which allows to calculate lifetime of carriers with temperature and structure design taking into account. Transport characteristics of the quantum cascade detectors have been computed using density matrix theory. As a result, we have obtained the system of ordinary differential equations describing dynamics of electron distribution functions and intersubband correlations. Managing carrier lifetime in quantum wells gives us possibility to control quantum efficiency and response.

A III-nitride based tunable hyperspectral detector pixel is described with the potential for real time detection in a wide range of wavelengths including near infrared (NIR). This detector has intrinsic hyperspectral pixels, each pixel being tunable in real time through a range of wavelengths determined by pixel design. This will eliminate the need for external gratings and filters, substantially decreasing weight, size, and complexity and increasing robustness. The single pixel detector discussed here offers the potential of wavelength spectroscopy from UV to NIR. To allow for dynamic tunability a multilayered Al_xGa_1-xN (0<x<1) forms the triangular potential barrier. Inclusion of In_xGa_1-xN as the absorbing layer offers detection in the IR region. The results of our experiments are complimented and explained using extensive device simulation.

Mid-Course Space Experiment (MSX) infrared (IR) observations in the earth limb were used to obtain spatial power spectral densities (PSDs) for five sensor bands over a wide range of earth limb background clutter conditions. These backgrounds include daytime, nighttime, terminator, aurora, polar mesospheric cloud, atmospheric gravity wave, stratospheric warming, airglow, and other observations collected over approximately 100 episodic data collection events. Using a subset of detectors and restricting detector tangent altitude variations, a total of more than 33,000 high-quality PSDs were generated. For infrared detection of unresolved objects where the solid angle of the object is much smaller than the instantaneous field-of-view of a sensor element, the spectral component at high spatial frequencies is a critical metric. PSDs were therefore constructed in the spatial domain using one minute data segments, which allowed spatial scale assessment from 0.01-10 cycles/km. PSDs that met the clutter model selection criteria were identified, accumulated, and processed to obtain a small set of empirical, altitude-based model parameters. We describe the MSX sensor bands, data and data processing employed for PSD generation and final reduction to obtain model parameters. Key model features are discussed with emphasis on object detection against stressing limb backgrounds. The model was constructed in a way that facilitates optical design and system engineering application. In particular, it may be used to address Space Situational Awareness (SSA) questions.

Beginning in the mid 30s of the last century german engineers designed and built a lot of optoelectronic devices which were used in the 2nd world war. Research was done also in the field of heat bearing devices (also known as Wärmepeilgeräte) that worked in a really simple but nonetheless reliable way. They will be the main emphasis of this paper.

Although originally developed for astronomical applications, the space qualification and availability of the Teledyne HAWAII detector make it appealing for high-precision Earth-observing systems such as the carbon monoxide correlation radiometer required for GEO-CAPE. In this shot noise-limited application, the signal-to-noise ratio of a co-averaged measurement is driven by the detector's temporal stability. To assess the stability, we operated the H2RG under monitored blackbody illumination. The Teledyne SIDECAR ASIC provided 16-bit digitization and clocking for integration times faster than the frame conversion time. With proper application of reference signals, the co-averaging of hundreds of frames is possible. Integrations of one-quarter of the full well depth can attain precision to the 200 ppm level in the co-averaged result. For integrations above three-quarters the well depth, the precision reaches 111 ppm.

A double beam IR detector is developed for light hydrocarbons concentration measurement in emissions from storage vessels during oil and oil products storage and transportation. It was concluded on the basis of chromatogram that main crude losses from evaporation are the share of hydrocarbons light ends from methane to decane. Detector operation is based on spectral transparency measurement in the infrared spectra absorption range. Operational wavelength of infrared radiation makes 3.4 μm. measurement principle is based on concentration calculation proceed from molecule absorption cross-section, optical path length between light emitted diode and reference and signal photodiodes as well as from value of measured signal transmitted through gaging volume. The novel of offering device is an actual paraffin hydrocarbons concentration measurement in emissions and continuous and automatic environment quality control.

With a transparency window up to 6 μm, sapphire can serve as a platform to support silicon photonic integrated circuit in MWIR. Planar waveguide devices based on silicon-on-sapphire (SOS) are emerging as a bridge between MWIR and SWIR through frequency band conversion process. While these devices are widely proposed to amplify MWIR signals and generate MWIR source, it can also be inversely utilized to achieve MWIR light detection. Here MWIR signals are down-converted to telecommunication wavelength (1.55 μm) through SOS waveguides and indirectly detected by SWIR detectors. Since detectors at telecommunication wavelengths exhibit superior performances in terms of speed, noise and sensitivity, the indirect detection scheme can be a promising candidate to improve the detection performance. In this report, we analyze performance of the indirect detection of MWIR signals by wavelength conversion in SOS waveguides. Particularly we modeled and compared the noise performance of the indirect detection with direct detection using state-of-the-art MWIR detectors. We show that, in addition to advantages of room temperature and high speed operation, the proposed indirect detection can improve the electrical signal-to-noise ratio up to 50dB, 23dB and 4dB compared to direct detection by PbSe, HgCdTe and InSb detectors respectively. The improvement is more pronounced in detection of weak MWIR signals.

We demonstrate a novel spectral imaging device based on an imaging Fourier transform spectrometer (FTS) with phase delays electro-optically controlled by fast tuning liquid crystal (LC) elements. The electro-optic (EO) tunable multispectral/hyperspectral imaging give the spectral imager significant advantages, including reduction in size and mass for simultaneous 2D spectral imaging, with a high spatial and spectral resolution. The technology is made very attractive for its potential military, medical and remote sensing applications where hyperspectral imaging plays a significant role in detection.

We will show how optical coherence tomography (OCT) can be used as a tool for non-destructive testing and evaluation of painted metallic materials. This technique is particularly suited for highly scattering material due to the gated nature of OCT.

The Jet Propulsion Laboratory is currently developing an end-to-end instrument which will provide a proof of concept prototype vehicle for a high data rate, multi-channel, thermal instrument in support of the Hyperspectral Infrared Imager (HyspIRI)-Thermal Infrared (TIR) space mission. HyspIRI mission was recommended by the National Research Council Decadal Survey (DS). The HyspIRI mission includes a visible shortwave infrared (SWIR) pushboom spectrometer and a multispectral whiskbroom thermal infrared (TIR) imager. The prototype testbed instrument addressed in this effort will only support the TIR. Data from the HyspIRI mission will be used to address key science questions related to the Solid Earth and Carbon Cycle and Ecosystems focus areas of the NASA Science Mission Directorate. Current designs for the HyspIRI-TIR space borne imager utilize eight spectral bands delineated with filters. The system will have 60m ground resolution, 200mK NEDT, 0.5C absolute temperature resolution with a 5-day repeat from LEO orbit. The prototype instrument will use mercury cadmium telluride (MCT) technology at the focal plane array in time delay integration mode. A custom read out integrated circuit (ROIC) will provide the high speed readout hence high data rates needed for the 5 day repeat. The current HyspIRI requirements dictate a ground knowledge measurement of 30m, so the prototype instrument will tackle this problem with a newly developed interferometeric metrology system. This will provide an absolute measurement of the scanning mirror to an order of magnitude better than conventional optical encoders. This will minimize the reliance on ground control points hence minimizing postprocessing (e.g. geo-rectification computations).

The Landsat missions are the longest continuous record of changes in the Earth's surface as seen from space. The next follow-on activity is the Landsat Data Continuity Mission (LDCM). The LDCM objective is to extend the ability to detect and quantitatively characterize changes on the global land surface at a scale where natural and man-made causes of change can be detected and differentiated. The Operational Land Imager (OLI) is one of two instruments on the LDCM spacecraft. OLI will produce science data for the reflective bands, which include 6 visible and near-infrared (VNIR) and 3 short-wave infrared (SWIR) bands. The OLI instrument utilizes a pushbroom design with 15.5 degree field of view. As a result, the OLI Focal Plane Array (FPA) cross track dimension is large, and the FPA is a critical technology for the success of the mission. The FPA contains 14 critically aligned Focal Plane Modules (FPM) and consists of 6916 imaging pixels in each of the 8 multi-spectral bands, and 13,832 imaging pixels in the panchromatic band. Prior to integration into the FPA, the FPMs were characterized for radiometric, spectral, and spatial performance. The Flight FPA has been built and its performance has also been characterized. In this paper, the critical attributes of the FPMs and FPA are highlighted. Detailed description of the FPM and FPA test sets are provided. The performance results that demonstrate compliance to the science mission requirements are presented.

Growth of ZnTe and HgCdSe on Si has been pursued using molecular beam epitaxy (MBE) as a new class of IR materials. Besides, ZnTe/Si can also be used as a lattice-matching, large area and low cost alternate substrate for other III-V and II-VI compound semiconductors, such as GaSb based type-II superlattice materials around 6.1A. We report in this paper our systematic studies on MBE growth conditions for ZnTe(211) on Si and highlights of MBE growth of HgCdSe on ZnTe/Si. A close to optimal growth window has been established for MBE growth of ZnTe(211)/Si(211) to achieve high crystalline quality, low defect and dislocation densities as well as excellent surface morphology. Using this baseline MBE growth process, we are able to obtain ZnTe(211)/Si wafers with X-ray full-width at half-maximum (FWHM) as low as 70 arcsec, low dislocation density (~105 cm^-2) and defect density (1000 cm^-2).

Much progress has been made in developing high quality HgCdTe/Si for large area focal plane array (FPA) applications. However, even with all the material advances made to date, there is no guarantee that this technology will be mature enough to meet the stringent FPA specifications required for long wavelength infrared (LWIR) systems. With this in mind, the Army Research Laboratory (ARL) has begun investigating HgCdSe material for infrared (IR) applications. Analogous to HgCdTe, HgCdSe is a tunable semiconductor that can detect any wavelength of IR radiation through control of the alloy composition. In addition, several mature, large area bulk III-V substrates are nearly latticematched to HgCdSe giving this system a possible advantage over HgCdTe in which no scalable, bulk substrate technology exists. We have initiated a study of the growth of HgCdSe using molecular beam epitaxy (MBE). Growth temperature and material flux ratios were varied to ascertain the best growth conditions and study defect formation. Smooth surface morphology has been achieved using a growth temperature much lower than HgCdTe. Preliminary data suggest a linear relationship between the Se/Cd flux ratio used during growth and the cut-off wavelength as measured by FTIR.

EO/IR Sensors and imagers using nanostructure based materials are being developed for a variety of Defense Applications. In this paper, we will discuss recent modeling effort and the experimental work under way for development of next generation carbon nanostructure based infrared detectors and arrays. We will discuss detector concepts that will provide next generation high performance, high frame rate, and uncooled nanobolometer for MWIR and LWIR bands. The critical technologies being developed include carbon nanostructure growth, characterization, optical and electronic properties that show the feasibility for IR detection. Experimental results on CNT nanostructures will be presented. We will discuss the path forward to demonstrate enhanced IR sensitivity and larger arrays.

In recent years a substantial amount of research has focused on the mechanical and electro-optical properties of ZnO nanowires (NWs). Initially, a significant portion of the work involved developing either single NWs or NW arrays for photo detection at ultraviolet (UV) wavelengths, and the innovation and performance of such devices have subsequently and progressively advanced. In addition, several new areas of ZnO NW research have since appeared, with energy harvesting at the forefront. The piezoelectric potential of nanowires has been a source of considerable interest, and novel concepts have been reported, including devices that convert thermal energy and sound waves into electrical power. In this paper we will address recent work (mostly published within the past couple years) on both ZnO NW based UV photodetectors and energy harvesting, seeking in the process to identify notable and innovative features that are advancing ZnO NW technology and nanodevice performance.

Uncooled infrared sensor markets have grown dramatically over the past decade due to significant improvements in sensor performance, producibility and cost reductions. Current uncooled sensors are dominated by VOx and amorphous silicon based microbolometers with spectral responses in the 7-14 μm wavelength region (LWIR). The majority of uncooled microbolometer focal plane array (UFPA) formats currently in production are 160x120, 320x240, 640x480 with 20 to 38 um pixel pitch. Most suppliers have reported good UFPA performance with less than 50 mK NETD(f/1 optics, 30 -60 Hz frame rates). Recently, 17 μm pixel pitch UFPAs have been introduced to the market. The smaller detector pixel pitch allows manufacturing of larger format such as 1024x768 UFPAs without photolithographic stitching. In the past, uncooled IR sensor developments were primarily driven by military needs; however, as low cost uncooled sensors began to proliferate in the commercial market, uncooled sensors with FPA formats of 320x240 and smaller are rapidly becoming commodity items. Reduction of sensor system size, weight, and power (SWaP) as well as cost is the key driver for the next generation of uncooled sensors. This paper presents a brief overview of the uncooled sensors status, developmental trends and challenges facing the industry.

When driving a vehicle, people use the central vision both to plan ahead and monitor their performance feedback (research by Donges, 1978 [1], and after). Discussion is ongoing if making eye movements do more than gathering information. Moving eyes may also prepare the following body movements like steering. Different paradigms exist to explore vision in driving. Our perspective was to quantify eye movements and fixation patterns of different proficiency individuals, a driving learner, a novice, an experienced driver and a European level car racer. Thus for safety reasons we started by asking them to follow a video tour through a known city, remote from an infrared eye tracker sampling at 250 Hz. We report that gaze strategy of an experienced driver differs qualitatively from that of an automobile sports master. Quantitative differences only were found between the latter and a driving learner or a novice driver. Experience in a motor action provides skills different from sports training. We are aiming at testing this finding in real world driving.

As microbolometer pixel dimensions for infrared imagers continue to decrease, the need for full-wave analysis in the design process is enhanced. Using reflectance as the validation point, an electromagnetic model of a dual-layer microbolometer pixel design was created for a 25 μm pixel design, and an in-depth study of the design was performed. With this model validated, further explorations were completed with a reduced size pixel. While simulating multiple variations of specific parameters, such as bridge thickness, upper and lower cavity heights, and different absorber configurations, a new evaluation metric of dissipated power in the structure was studied. This metric, provided by finite element analysis, provides great insight into absorption properties within the microbolometer structure, properties that cannot be directly measured but that are critical to the functionality of the pixel design. In this paper parametric analysis of microbolometer pixel designs are presented via both reflectance and dissipated power full-wave analysis.

The cytochrome c (protein) thin film on the oxide surface has been reported high temperature coefficient of resistance (TCR). The protein thin film resistance acts as exponential grow under the constant voltage bias. The experimental results showed that the TCR exceeded 20% 1/K, which is 5times higher than popular vanadium oxide (VOx). We also found the protein thin film can be attached on to the SU8 photoresist surface by changing the SU8 surface more hydrophilic and simple spinning coat technique. The cytochrome c thin film on SU8 also showed the high TCR. With easy fabrication methods and lower thermal conductivity of SU8 and protein, we believe that it is possible to fabricate new generation microbolometer based on cytochrome c protein and SU-8 photoresist.

Infrared thermography is a promising solution that can help improve our lives. However, most of the common materials used to fabricate lenses, such as glass, are opaque in the infrared range. Silicon and germanium are better solutions. But shaping these two materials are truly complicated and time-consuming. Many research works have been devoted to develop cost-effective infrared lenses. Due to material restriction, traditional lenses to focus infrared light are expensive. On the other hand, we found that PMMA (Poly methyl methacrylate) is an ubiquitous polymer material. It is cheap and transparent in mid-IR range. More importantly, liquid PMMA can be shaped and solidified easily. Therefore, we chose PMMA as the material to design and make our IR lenses. In this paper, we choose PMMA and discuss its optical properties in mid-IR range. We believe that PMMA is a highly potential material for low-cost infrared lenses. Also, we show simulation results of an f/1.39, diameter = 11mm and focal length = 13.9mm Fresnel lens made by PMMA to demonstrate its feasibility. We made a PMMA Fresnel lens, by using MEMS processes and embossing. The experimental results agree well with simulation data.

A novel method of simultaneous multi-wavelength-band common-path optical frequency domain imaging is proposed for spectroscopic applications. Simultaneous multi-band wavelength tuning can be performed by using multiple fiber-ring cavities with corresponding optical semiconductor amplifier as their gain mediums and narrowband optical filters with a single polygonal scanner for synchronization. A simultaneous 1310/1550 dual-band swept laser source is constructed as a proof concept prototype. Broadband 1310/1550 wavelength-division multiplexing is used for coupling two wavelengths into a common-path single-mode GRIN-lensed fiber probe to form a dual-band common-path optical frequency domain imaging. Simultaneous imaging at 1310 and 1550 nm is achieved by using a depth ratio correction method. This technique allows potential for in vivo endoscopic high-speed functional optical frequency domain imaging with high quality spectroscopic contrast with low computational costs. On the other hand, the common path configuration is able to suppress common mode noise and potentially implement high stability quantitative phase measurements.

A sophisticated technique to measure extensive air showers initiated by ultra-high-energy cosmic rays is by means of fluorescence telescopes. Secondary particles of the air shower excite nitrogen molecules of the atmosphere, which emit fluorescence light when they de-excite. Due to their high photon detection efficiency (PDE) silicon photomultipliers (SiPMs) promise to increase the sensitivity of todays fluorescence telescopes which use photomultiplier tubes - for example the fluorescence detector of the Pierre Auger Observatory. On the other hand drawbacks like a small sensitive area, a strong temperature dependency and a high noise rate have to be managed. We present plans for a prototype fluorescence telescope using SiPMs and a special light collecting optical system of Winston cones to increase the sensitive area. In this context we made measurements of the relative PDE of SiPMs depending on the incident angle of light. The results agree with calculations based on the Fresnel equations. Furthermore, measurements of the brightness of the night sky are presented since this photon flux is the main background to the fluorescence signals of the extensive air showers. To compensate the temperature dependency of the SiPM, frontend electronics make use of temperature sensors and microcontrollers to directly adjust the bias-voltage according to the thermal conditions. To reduce the noise rate we study the coincidence of several SiPMs signals triggered by cosmic ray events. By summing up these signals the SiPMs will constitute a single pixel of the fluorescence telescope.

Single-photon imaging detectors promise the ultimate in sensitivity by eliminating read noise. These devices could provide extraordinary benefits for photon-starved applications, e.g., imaging exoplanets, fast wavefront sensing, and probing the human body through transluminescence. Recent implementations are often in the form of sparse arrays that have less-than-unity fill factor. For imaging, fill factor is typically enhanced by using microlenses, at the expense of photometric and spatial information loss near the edges and corners of the pixels. Other challenges include afterpulsing and the potential for photon self-retriggering. Both effects produce spurious signal that can degrade the signal-to-noise ratio. This paper reviews development and potential application of single-photon-counting detectors, including highlights of initiatives in the Center for Detectors at the Rochester Institute of Technology and MIT Lincoln Laboratory. Current projects include single-photon-counting imaging detectors for the Thirty Meter Telescope, a future NASA terrestrial exoplanet mission, and imaging LIDAR detectors for planetary and Earth science space missions.

This paper describes single photon detection for Ge on Si separate-absorption-charge-multiplication (SACM) avalanche photodiodes and advances in quenching for InP/InGaAs single photon avalanche diodes.

An InGaAs/InAlAs/InP single photon avalanche detector featuring an InAlAs Transient Carrier Buffer (TCB) layer to tentatively stop avalanche-generated electrons as a negative feedback mechanism demonstrates self-quenching and selfrecovering capabilities. The escape rate of those stopped avalanche electrons from the TCB barrier determines the recovery time and thus data rate of the detector. We show that thermionic emission and tunneling are key mechanisms in the self-recovery process. The recovery time increases with the decrease of temperature and the decrease of applied bias.

Active depth imaging approaches have numerous potential applications in a number of disciplines, including environmental sensing, manufacturing and defense. The high sensitivity and picosecond timing resolution of the singlephoton counting technique can provide distinct advantages in the trade-offs between required illumination power, range, depth resolution, and data acquisition durations. These considerations must also address requirements for eye-safety, especially in applications requiring outdoor, kilometer range sensing. We present a scanning time-of-flight imager based on high repetition-rate (>MHz) pulsed illumination and a silicon single-photon detector. In advanced photon-counting experiments, we have employed the system for unambiguous range resolution at several kilometer target distance, multiple-surface resolution based on adaptive algorithms, and a cumulative data acquisition method that facilitates detector characterization and evaluation. We consider a range of optical design configurations and discuss the performance trade-offs in more detail. Much of this work has been performed at wavelengths around 850nm for convenient use with Si-based single photon avalanche diode detectors, however we will also discuss the performance at wavelengths around 1550 nm employing superconducting nanowire single photon detectors. The extension of this depth profiling technique to longer wavelengths will lead to relaxed eye safety requirements, reduced solar background levels and improvements in atmospheric transmission.

The illumination-angle-dependent absorptance was determined for three types of superconducting-nanowire singlephoton detector (SNSPD) designs: 1. periodic bare niobium-nitride (NbN) stripes with dimensions of conventional SNSPDs, 2. the same NbN patterns integrated with ~quarter-wavelength hydrogensilsesquioxane-filled nano- cavity, 3. similar cavity-integrated structures covered by a thin gold reflector. A three-dimensional finite-element method was applied to determine the optical response and near-field distribution as a function of p-polarized light illumination orientations specified by polar-angle, φ, and azimuthal-angle, γ. The numerical results proved that the NbN absorptance might be maximized via simultaneous optimization of the polar and azimuthal illumination angles. Complementary transfer-matrix-method calculations were performed on analogous film-stacks to uncover the phenomena contributing to the appearance of extrema on the optical response of NbN-patterns in P-structure-configuration. This comparative study showed that the absorptance of bare NbN patterns is zero at the angle corresponding to total internal reflection (TIR). In cavity-integrated structures the NbN absorptance curve indicates a maximum at the same orientation due to the phase shift introduced by the quarter-wavelength HSQ layer. The reflector promotes the NbN absorptance at small polar angles, but the available absorptance is limited by attenuated TIR in polar angle-intervals, where surface modes are excited on the gold film.

Topographic mapping lidar instruments must be able to detect extremely weak laser return signals from high altitudes including orbital distance. The signals have a wide dynamic range caused by the variability in atmospheric transmission and surface reflectance under a fast moving spacecraft. Ideally, lidar detectors should be able to detect laser signal return pulses at the single photon level and produce linear output for multiple photon events. Silicon avalanche photodiode (APD) detectors have been used in most space lidar receivers to date. Their sensitivity is typically hundreds of photons per pulse, and is limited by the quantum efficiency, APD gain noise, dark current, and preamplifier noise. NASA is pursuing three approaches for a 16-channel laser photoreceiver for use on the next generation direct-detection airborne and spaceborne lidars. We present our measurement results and a comparison of their performance.

The false count rate of a single-photon-sensitive photoreceiver consisting of a high-gain, low-excess-noise linear-mode InGaAs avalanche photodiode (APD) and a high-bandwidth transimpedance amplifier (TIA) is fit to a statistical model. The peak height distribution of the APD's multiplied dark current is approximated by the weighted sum of McIntyre distributions, each characterizing dark current generated at a different location within the APD's junction. The peak height distribution approximated in this way is convolved with a Gaussian distribution representing the input-referred noise of the TIA to generate the statistical distribution of the uncorrelated sum. The cumulative distribution function (CDF) representing count probability as a function of detection threshold is computed, and the CDF model fit to empirical false count data. It is found that only k=0 McIntyre distributions fit the empirically measured CDF at high detection threshold, and that false count rate drops faster than photon count rate as detection threshold is raised. Once fit to empirical false count data, the model predicts the improvement of the false count rate to be expected from reductions in TIA noise and APD dark current. Improvement by at least three orders of magnitude is thought feasible with further manufacturing development and a capacitive-feedback TIA (CTIA).

Over the past few years there has been a growing interest in monolithic arrays of single photon avalanche diodes (SPAD) for spatially resolved detection of faint ultrafast optical signals. SPADs implemented in planar technologies offer the typical advantages of microelectronic devices (small size, ruggedness, low voltage, low power, etc.). Furthermore, they have inherently higher photon detection efficiency than PMTs and are able to provide, beside sensitivities down to single-photons, very high acquisition speeds. Although currently available silicon devices reached remarkable performance, nevertheless further improvements are needed in order to meet the requirements of most demanding timeresolved techniques, it is necessary to face problems like electrical crosstalk between adjacent pixel, high detection efficiency in the red spectral range, large area, low dark counting rate. Moreover to develop array with high number of pixel became more and more important to develop all the TCSPC electronics with picosecond resolution to create a new family of detection system for TCSPC applications. Recent advances in our research on single photon time resolved array is here presented.

We report the synthesis, fabrication and testing of a 320 × 256 focal plane array (FPA) of back-illuminated, solarblind, p-i-n, AlxGa1-xN-based detectors, fully realized within our research laboratory. We implemented a novel pulsed atomic layer deposition technique for the metalorganic chemical vapor deposition (MOCVD) growth of crackfree, thick, and high Al composition AlxGa1-xN layers. Following the growth, the wafer was processed into a 320 × 256 array of 25 μm × 25 μm pixels on a 30 μm pixel-pitch and surrounding mini-arrays. A diagnostic mini-array was hybridized to a silicon fan-out chip to allow the study of electrical and optical characteristics of discrete pixels of the FPA. At a reverse bias of 1 V, an average photodetector exhibited a low dark current density of 1.12×10-8 A/cm2. Solar-blind operation is observed throughout the array with peak detection occurring at wavelengths of 256 nm and lower and falling off three orders of magnitude by 285 nm. After indium bump deposition and dicing, the FPA is hybridized to a matching ISC 9809 readout integrated circuit (ROIC). By developing a novel masking technology, we significantly reduced the visible response of the ROIC and thus the need for external filtering to achieve solar- and visible-blind operation is eliminated. This allowed the FPA to achieve high external quantum efficiency (EQE): at 254 nm, average pixels showed unbiased peak responsivity of 75 mA/W, which corresponds to an EQE of ~37%. Finally, the uniformity of the FPA and imaging properties are investigated.