This PDF file contains the front matter associated with SPIE Proceedings Volume 8704, including the Title Page, Copyright information, Table of Contents, Introduction, and the Conference Committee listing.

We have fabricated low-dark-current InGaAs photodetectors utilizing an epitaxial structure incorporating an InAlGaAs passivation layer and a simple mesa isolation process, and requiring no implant or diffusion steps. At 295 K, areal and perimeter dark current contributions are 15 nA/cm² and 9 pA/cm, respectively, in devices with large aspect ratios biased at -0.1 V. High responsivity was achieved even at zero bias in these devices. Devices were modeled using a commercial drift-diffusion simulator. Good fits to reverse dark current-voltage measurements were obtained using a model that included both bulk and interfacial generation mechanisms. Assuming similar electron and hole Shockley-Read-Hall lifetimes, dark current under small reverse bias are consistent with generation at the interface between the absorber and underlying layers. With increasing negative bias a large increase in dark current is associated with depletion near the InAlGaAs/absorber interface, while small increases in current at large reverse bias suggest long Shockley-Read-Hall lifetimes in the absorber. Forward biasing of these devices results in efficient injection of minority carrier holes into the absorber region, mimicking photogeneration and providing a method to predict the performance of illuminated detector arrays.

SWIR detection band benefits from natural (sun, night glow, thermal radiation) or artificial (eye safe lasers) photons sources combined to low atmospheric absorption and specific contrast compared to visible wavelengths. It gives the opportunity to address a large spectrum of applications such as defense and security (night vision, active imaging), space (earth observation), transport (automotive safety) or industry (non destructive process control). InGaAs material appears as a good candidate to satisfy SWIR detection needs. The lattice matching with InP constitutes a double advantage to this material: attractive production capacity and uncooled operation thanks to low dark current level induced by high quality material. The study of InGaAs FPA has begun few years ago with III-VLab, gathering expertise in InGaAs material growth and imaging technology respectively from Alcatel-Lucent and Thales, its two mother companies. This work has led to put quickly on the market a 320x256 InGaAs module. The recent transfer of imagery activities from III-VLab to Sofradir allows developing new high performances products, satisfying customers’ new requirements. Especially, a 640x512 InGaAs module with a pitch of 15µm is actually under development to fill the needs of low light level imaging.

Xenics has designed and manufactured a 1280*1024 pixel, 17 µm pitch InGaAs array for SWIR imaging in the [0.9 - 1.7 µm] range. It will report on the first characterization results of the device. As usual for this type of room temperature operated SWIR image sensors, the detector interface is based on a CTIA stage, yielding excellent linearity, a low detector bias and hence a low and stable dark current combined with low image lag. The charge to voltage conversion factor is 40 µV/e^-. The pixel interface scheme contains a CDS circuit in order to reduce the kTC noise and common mode effects. The noise is expected to be below 30 e^-_rms in linear mode, resulting in a dynamic range < 60 dB. Additionally the linear dynamic range is complemented with a high dynamic range logarithmic response with a saturation level < 5 nA/pixel. The information in the pixel matrix can be read via 2, 4 or 8 outputs, yielding a maximum full frame rate between 50 and 200 Hz. Each output is operating at 40 MHz pixel rate. The outputs are differential with a common mode voltage of 0.9 V and an adjustable output swing of 2 V_ptp. Nevertheless the power dissipation shall be below 330 mW.

Size, weight, and power (i.e.: Small SWaP) are increasingly recognized as the primary drivers in the enablement of high-volume man-portable SWIR imaging systems. Several low power advancements are described for a 1.3 Mpixel SWIR imaging platform capable of operating at a power budget of approximately 1.7 microwatts/pixel. Techniques such as reducing overall system memory bandwidth, low-voltage operation, and parameterized non-uniform corrections (PNUC) are described. Even at such reduced power consumption, full imaging performance at 30 frames per second is realized across an extended operating range of -40°C to 70°C.

SiOnyx has developed visible and infrared CMOS image sensors leveraging a proprietary ultrafast laser semiconductor process technology. This technology demonstrates 10 fold improvements in infrared sensitivity over incumbent imaging technology while maintaining complete compatibility with standard CMOS image sensor process flows. Furthermore, these sensitivity enhancements are achieved on a focal plane with state of the art noise performance of 2 electrons/pixel. By capturing light in the visible regime as well as infrared light from the night glow, this sensor technology provides imaging in daytime through twilight and into nighttime conditions. The measured 10x quantum efficiency at the critical 1064 nm laser node enables see spot imaging capabilities in a variety of ambient conditions. The spectral sensitivity is from 400 to 1200 nm.

We report crosstalk in 1 mm diameter and 2 mm diameter quad InGaAs photodiodes having quadrant-to-quadrant separation of 15 μm, 20 μm, and 25 μm. This crosstalk is a combination of resistive and capacitive coupling between the photodiode quadrants and varies widely on the combination on device diameter, quadrant-to-quadrant separation, illumination conditions, and modulation frequency. Thus, the position sensing accuracy is heavily influenced by the operating conditions of the quad photodiode.

This paper presents novel unit cell architecture for short wave infrared (SWIR) imaging applications. It has two input stages which are CTIA and SFD covering for both respectively low and high light levels and automatic input stage selection circuitry that chooses best input stage. A user can select 2 modes for FPA manual and automatic mode. In manual mode, user can set CTIA or SFD for all pixels according to user needs. In automatic mode, each pixel selects input stage itself according to light level. Automatic input stage selection for each pixel brings high SNR level and low noise along with highest possible dynamic range. Standard CMOS 0.18µm TSMC technology is used to realize unit cell. In the architecture of unit cell, circuit level techniques are used to optimize layout size.

Since many years AIM delivers IR-modules for army applications like pilotage, weapon sights, UAVs or vehicle platforms. State-of-the-art 640x512, 15μm pitch detector modules are in production in manifold configurations optimized for specific key requirements on system level. This is possible due to a modular design, which is best suited to meet the diversity of system needs in army applications. Examples are optimization of detector-dewar length for gimbal applications, size weight and power reduction for UAVs or lifetime enhancement for vehicle platforms. In 2012 AIM presented first prototypes of megapixel detectors (1280x1024, 15μm pitch) for both spectral bands MWIR and LWIR. These large format detector arrays fulfill the demand for higher spatial resolution, which is requested for applications like rotorcraft pilotage, persistent surveillance or tasks like determination of threat level in personnel targets. Recently, a new tactical dewar has been developed for the 1280x1024 detector arrays. It is designed to withstand environmental stresses and, at the same time, to quest for a compact overall package. Furthermore, the idea of a modular design will be even more emphasized. Integration of different cooler types, like AIM’s SX095 or rotary integral, will be possible without modification of the dewar. The paper will present development status of large format IR-modules at AIM as well as performance data and configuration considerations with respect to army applications.

Cooled IR technologies that offer high performances are at the top of DEFIR’s priority list. We have been pursuing further infrared developments on future MWIR detectors, such as the VGA format HOT detector that operates at 150K and the 10μm pitch IR detector which gives us a leading position in innovation In the same time Scorpio LW expands Sofradir's line of small pixel pitch TV format IR detectors from the mid-wavelength to the long-wavelength, broadening the performance attributes of its long wave IR product line. Finally, our dual band MW-LW QWIP detectors (25μm, 384×288 pixels) benefit to tactical platforms giving an all-weather performance and increasing flexibility in the presence of battlefield obscurants. These detectors are designed for long-range surveillance equipment, commander or gunner sights, ground-toground missile launchers and other applications that require higher resolution and sensitivity to improve reconnaissance and target identification. This paper discusses the system level performance in each detector type.

Sensor technologies are undergoing revolutionary advances, as seen in the rapid growth of multispectral methodologies. Increases in spatial, spectral, and temporal resolution, and in breadth of spectral coverage, render feasible sensors that function with unprecedented performance. A system was developed that addresses many of the key hardware requirements for a practical dual-band multispectral acquisition system, including wide field of view and spectral/temporal shift between dual bands. The system was designed using a novel dichroic beam splitter and dual band-pass filter configuration that creates two side-by-side images of a scene on a single sensor. A high-speed CMOS sensor was used to simultaneously capture data from the entire scene in both spectral bands using a short focal-length lens that provided a wide field-of-view. The beam-splitter components were arranged such that the two images were maintained in optical alignment and real-time intra-band processing could be carried out using only simple arithmetic on the image halves. An experiment related to limitations of the system to address multispectral detection requirements was performed. This characterized the system’s low spectral variation across its wide field of view. This paper provides lessons learned on the general limitation of key hardware components required for multispectral muzzle flash detection, using the system as a hardware example combined with simulated multispectral muzzle flash and background signatures.

A fourth generation of SWIR based optical detection and warning means is presented as the EL/O–5220 OTHELLO passive Optical Threat Locator, which detects and precisely finds directions towards a source of battle tank gun fire and missile (e.g. Anti-Tank Guided Missiles (ATGMs) Rocket Propelled Grenades (RPGs)) launch events in the battlefield. OTHELLO hardware is described followed by an explanation of some inherent advantages of SWIR imagers as building blocks for optical detection systems mounted on ground military vehicles at harsh and demanding operating conditions. Finally we describe possible application of OTHELLO with radar systems.

A highly ruggedized infra-red sensor module has been developed which is suitable for a variety of fast framing applications in hostile fire detection and in scientific or industrial metrology. The sensor offers <1000fps in the full 384x384 format and useful images up to 6500fps in smaller formats. High operability for either mid-wave or long-wave IR applications is assured with high performance MOVPE fabrication technology. The paper reports design concepts and performance data for the MW variant.

SWIR cameras offer the advantage of higher resolution and smaller optical systems than conventional mid and far infrared optical systems. With the ability of seeing at low illumination conditions at the near infrared region, it can provide the detection of covert lasers. The ability of laser detection introduces the risk of sensor damage when the laser power is above a certain threat level. Smart protection is therefore needed, that is transparent for low laser intensities and limit or block the high laser intensities, and is effective over a wide band of wavelengths. We developed an Optical Power Control (OPC) device that reduces laser power threat to a safe level for a variety of optical systems. The talk presents a novel technology for protection of SWIR cameras against laser threats.

The thermal imager ATTICA was designed to fit into the thermal sights of the new German Infantry tank PUMA. The flexible approach for the optical concept, using different folding mirrors allows meeting the different available space requirements for thermal sights also of other tanks like the main battle tank Leopard 2 and the infantry fighting vehicle Marder. These tanks are going to be upgraded. The flexible concepts of the thermal imager optics as well as the mechanical packing solutions for the different space volumes of the commander and gunner sights of the vehicles are discussed.

Requirements for vehicle mounted infrared sensors, especially as imagers evolve to high definition (HD) format will be detailed and analyzed. Lessons learned from integrations of infrared sensors on armored vehicles, unarmored military vehicles and commercial automobiles will be discussed. Comparisons between sensors for driving and those for situation awareness, targeting and other functions will be presented. Conclusions will be drawn regarding future applications and installations. New business requirements for more advanced digital image processing algorithms in the sensor system will be discussed. Examples of these are smarter contrast/brightness adjustments algorithms, detail enhancement, intelligent blending (IR-Vis) modes, and augmented reality.

The paper introduces the analysis carried out by Selex ES (SE) for the development of a third generation IRST system based on large format MWIR sensors, separable in blue and red bands. In the feasibility study, physical constraints have been evaluated relying on different optics and scanning options. The goal is a system based on distributed heads to cover 360° with a resolution better than 0.3 mrad and high frame rate that allow to take advantage of the typical atmospheric phenomena of the maritime environment as scintillation and super and sub refraction. Two critical aspects were investigated: (i) the setting of an adequate scanning mechanism to assure a high frame rate and (ii) the stitching of the collected images while maintaining the bit-depth so as to avoid abrupt changes of SNR at the seams between two subsequent images.

Infrared sensor technology, high performance computing hardware and advanced detection and tracking algorithms have enabled a new generation of infrared warning systems for navy surface vessels. In this paper we describe Sea Spotter - a new third-generation naval IRST system, which is unique in offering a fully staring electro-optical imaging unit. Starting from naval IRST operational requirements, we describe the considerations and constraints that led us to the configuration of the sensor head and the supporting hardware. The second part of the paper is dedicated to the target acquisition methodology, including the use of originally developed machine learning technology for target acquisition and tracking.

Seven countries within the European Defence Agency (EDA) framework are joining effort in a four year project (2009-2013) on Detection in Urban scenario using Combined Airborne imaging Sensors (DUCAS). Data has been collected in a joint field trial including instrumentation for 3D mapping, hyperspectral and high resolution imagery together with in situ instrumentation for target, background and atmospheric characterization. Extensive analysis with respect to detection and classification has been performed. Progress in performance has been shown using combinations of hyperspectral and high spatial resolution sensors.

Based on a large experience, SOFRADIR is conducting major space programs covering all the wavelength range from visible to VLWIR as Sentinel projects in the frame of the GMES program or MTG detectors development and manufacturing for the future European meteorological satellites of third generation. In particular, new developments of MCT infrared detectors are currently made: • A new generation of SWIR hyperspectral detectors with a format of 1024x1024 / 15 µm pitch • Optimization of MCT performances for VLWIR spectral range aiming at new sounding missions • Developments of new infrared detectors for MTG program In this paper, a review of the main space programs conducted by SOFRADIR is presented with a particular emphasis on the last developments.

Vibration disturbances generated by cryocooler, representing in a series of harmonics, are critical issue in practical application. A control system including electronic circuit and mechanical actuator has been developed to attenuate the vibration. The control algorithm executes as a series of adaptive narrowband notch filters to reduce corresponding harmonics. The algorithm does not require actuator transfer function, thus ensure its adaptiveness. Using this algorithm, all the vibration harmonics of cryocooler were attenuated by a factor of more than 45.9 dB, i.e., the residual vibration force was reduced from 20.1Nrms to 0.102Nrms over the 300 Hz control bandwidth, the converging time is only less than 20 seconds, and the power consumption of mechanical actuator is less than half a watt. The vibration control system has achieved the general requirement of Infrared application.

The market of the sights for the 5.56 mm assault rifles is dominated by mainly three types of systems: TWS (Thermal Weapon Sight), the Pocket Scope with Weapon Mount and the Clip-on. The latter are designed primarily for special forces and snipers use, while the TWS design is triggered mainly by the DRI (Detection, Recognition, Identification) requirements. The Pocket Scope design is focused on respecting the SWaP (Size, Weight and Power dissipation) requirements. Compared to the TWS systems, for the last two years there was a significant technological growth of the Pocket Scope/Weapon Mount solutions, concentrated on the compression of the overall dimensions. The trend for the assault rifles is the use of small size/light weight (SWaP) IR sights, suitable mainly for close combat operations but also for extraordinary use as pocket scopes – handheld or helmet mounted. The latest developments made by Selex ES S.p.A. are responding precisely to the above-mentioned trend, through a miniaturized Day/Night sight embedding state-of-the art sensors and using standard protocols (USB 2.0, Bluetooth 4.0) for interfacing with PDAs, Wearable computers, etc., while maintaining the “shoot around the corner” capability. Indeed, inside the miniaturized Day/Night sight architecture, a wireless link using Bluetooth technology has been implemented to transmit the video streaming of the rifle sight to an helmet mounted display. The video of the rifle sight is transmitted only to the eye-piece of the soldier shouldering the rifle.

Situational awareness and precise targeting at day, night and severe weather conditions are key elements for mission success in asymmetric warfare. To support these capabilities for the dismounted soldier, AIM has developed a family of stand-alone thermal weapon sights based on high performance cooled IR-modules which are used e.g. in the infantryman of the future program of the German army (IdZ). The design driver for these sights is a long ID range <1500m for the NATO standard target to cover the operational range of a platoon with the engagement range of .50 cal rifles, 40mm AGLs or for reconnaissance tasks. The most recent sight WBZG has just entered into serial production for the IdZ enhanced system of the German army with additional capabilities like a wireless data link to the soldier backbone computer. Minimum size, weight and power (SWaP) are most critical requirements for the dismounted soldiers’ equipment and sometimes push a decision towards uncooled equipment with marginal performance referring to the outstanding challenges in current asymmetric warfare, e.g. the capability to distinguish between combatants and non-combatants in adequate ranges. To provide the uncompromised e/o performance with SWaP parameters close to uncooled, AIM has developed a new thermal weapon sight based on high operating temperature (HOT) MCT MWIR FPAs together with a new low power single piston stirling cooler. In basic operation the sight is used as a clip-on in front of the rifle scope. An additional eyepiece for stand-alone targeting with e.g. AGLs or a biocular version for relaxed surveillance will be available. The paper will present details of the technologies applied for such long range cooled sights with size, weight and power close to uncooled.

In late 2012 SSZ Camouflage Technology, AG, and Milliken and Company joined forces to bring apparel weight fabrics with infrared signature reduction to the US military, Homeland Security, and other law enforcement agencies. By significantly reducing the thermal infrared signature of soldiers wearing these fabrics, this technology goes beyond the current visual and near infrared range (NIR) to provide concealment in the mid wave infrared range (MWIR) and long wave infrared range (LWIR) thus reducing the risk of detection from thermal infrared imagers. This infrared camouflage technology can be incorporated into a variety of performance fabrics which can provide U.S. Military, Homeland Security, and law enforcement personnel with better concealment, adding yet another layer of protection to their uniforms.n late 2012 SSZ Camouflage Technology, AG, and Milliken and Company joined forces to bring apparel weight fabrics with

Further reduction of size, weight and power consumption of the High Operating Temperature (HOT) infrared (IR) Integrated Detector-Dewar-Cooler Assemblies (IDDCA) eventually calls for development of high-speed cryocoolers. In case of integral rotary design, the immediate penalty is the more intensive slapping of compression and expansion pistons along with intensification of micro collisions inherent for the operation of crank-slide linkages featuring ball bearings. Resulting from this is the generation of impulsive vibration export, the spectrum of which features the driving frequency along with numerous multiples covering the entire range of audible frequencies. In a typical design of an infrared imager, the metal light-weight enclosure accommodates a directly mounted IDDCA and an optical train, thus serving as an optical bench and heat sink. This usually results in excitation of structural resonances in the said enclosure and, therefore, in excessive noise generation compromising the aural stealth. The author presents the complex approach to a design of aural undetectable infrared imagers in which the IDDCA is mounted upon the imager enclosure through a silent pad. Special attention is paid to resolving the line of sight stability and heat sinking issues. The demonstration imager relying on Ricor K562S based IDDCA meets the most stringent requirement to 10 meters aural non-detectability distance (per MIL-STD 1474D, Level II) even during boost cooldown phase of operation.

We report a bias selectable dual-band mid-wave infrared (MWIR) and long-wave infrared (LWIR) co-located detector with 3 μm active region thickness per channel that is highly selective and can perform under high operating temperatures for the MWIR band. Under back-side illumination, a temperature evolution study of the MWIR detector’s electro-optical performance found the 300 K background-limit with 2π field-of-view to be achieved below operating temperatures of 160 K, at which the temperature’s 50% cutoff wavelength was 5.2 μm. The measured current reached the system limit of 0.1 pA at 110 K for 30 μm pixel-sized diodes. At 77 K, where the LWIR channel operated with a 50% cutoff wavelength at 11.2 μm, an LWIR selectivity of ∼17% was achieved in the MWIR wave band between 3 and 4.7 μm, making the detector highly selective.

Poor passivation on photodetectors can result in catastrophic failure of the device. Abrupt termination of mesa side walls during pixel definition generates dangling bonds that lead to inversion layers and surface traps leading to surface leakage currents that short circuit diode action. Good passivation, therefore, is critical in the fabrication of high performance devices. Silicondioxide has been the main stay of passivation for commercial photodetectors, deposited at high temperatures and high RF powers using plasma deposition techniques. In photodetectors based on III-V compounds, sulphur passivation has been shown to replace oxygen and saturate the dangling bonds. Despite its effectiveness, it degrades over time. More effort is required to create passivation layers which eliminate surface leakage current. In this work, we propose the use of sulphur based octadecanethiol (ODT), CH₃(CH₂)₁₇SH, as a passivation layer for the InAs/GaSb superlattice photodetectors that acts as a self assembled monolayer (SAM). ODT SAMs consist of a chain of 18 carbon atoms with a sulphur atom at its head. ODT Thiol coating is a simple process that consist of dipping the sample into the solution for a prescribed time. Excellent electrical performance of diodes tested confirm the effectiveness of the sulphur head stabilized by the intermolecular interaction due to van der Walls forces between the long chains of ODT SAM which results in highly stable ultrathin hydrocarbon layers without long term degradation.

To examine defects in InAs/GaSb type-II superlattices we investigated GaSb substrates and epitaxial InAs/GaSb layers by synchrotron white beam X-ray topography to characterize the distribution of threading dislocations. Those measurements are compared with wet chemical etch pit density measurements on GaSb substrates and InAs/GaSb type-II superlattices epitaxial layer structures. The technique uses a wet chemical etch process to decorate threading dislocations and an automated optical analyzing system for mapping the defect distribution. Dark current and noise measurements on processed InAs/GaSb type-II superlattice single element photo diodes reveal a generation-recombination limited dark current behavior without contributions by surface leakage currents for midwavelength infrared detectors. In the white noise part of the noise spectrum, the extracted diode noise closely matches the theoretically expected shot noise behavior. For diodes with an increased dark current in comparison to the dark current of generation-recombination limited material, the standard shot-noise model fails to describe the noise experimentally observed in the white part of the spectrum. Instead, we find that McIntyre’s noise model for avalanche multiplication processes fits the data quite well. We suggest that within high electric field domains localized around crystallographic defects, electrons initiate avalanche multiplication processes leading to increased dark current and excess noise.

Time-resolved photoluminescence (TRPL) is used to study the minority carrier lifetime in type-II superlattice (T2SL) infrared detector materials to investigate the recombination mechanisms, trap states and transport properties that currently limit their performance. Measurements of carrier lifetime have shown that InAs/Ga_1-xIn_xSb T2SLs are dominated by non-radiative Shockley-Read-Hall (SRH) recombination, resulting in short minority carrier lifetimes (10’s of nanoseconds at 77 K). A trap energy of ~60 meV above the valence band is identified in mid-wavelength infrared n-type InAs/Ga_1-xIn_xSb T2SLs, where trap saturation (non-exponential decay) is observed under high injection levels due to a significantly faster hole capture rate than electron capture rate. Lifetime measurements in “Ga-free” InAs/InAs_1-xSb_x T2SLs exhibit an order-of-magnitude increase in lifetime (100’s of nanoseconds at 77 K) with contributions from both radiative and non-radiative recombination. This improvement is attributed to the reduction of non-radiative recombination centers from the superlattice with the elimination of Ga and suggests that the SRH trap(s) limiting the carrier lifetime of InAs/Ga_1-xIn_xSb T2SLs is native to the Ga_1-xIn_xSb layer. Additionally, radiative recombination is observed in an InAs/GaSb T2SL using a sub-bandgap CW laser to saturate the SRH recombination centers, yielding a radiative lifetime of ~140 ns at 77 K. Since carrier transport is a concern in Ga-free T2SLs, it is investigated by studying samples grown with and without barriers (to contain injected carriers to the absorber region). It is determined that carrier transport is poor in InAs/InAs_1-xSb_x T2SLs because negligible differences are observed in the carrier lifetime.

We describe a relationship between the noise characterization and activation energy of InAs/GaSb superlattice Mid-Wavelength-Infrared photodiodes for different passivation materials applied to the device. The noise measurements exhibited a frequency dependent plateau (i.e. 1/f-noise characteristic) for unpassivated as well as Si₃N₄ passivated samples whereas 1/f-type low noise suppression (i.e. frequency independent plateau) with a noise current reduction of more than one order of magnitude was observed for SiO₂ passivation. For reverse bias values below -0.15V, the classical Schottky-noise calculation alone did not appear to describe the noise mechanism in a SL noise behavior, which shows a divergence between theoretically and experimentally determined noise values. We identify that, the additional noise appears, with and without passivation, at the surface activation energy of < 60 meV and is inversely proportional to the reverse bias. This is believed to be caused by the surface dangling-bonds (as well as surface states) whose response is controlled by the applied reverse bias. The calculated noise characteristics showed a good agreement with the experimental data.

A VGA format type-II superlattice focal plane array (FPA) for the mid-wave infrared (MWIR) atmospheric window has been designed, manufactured and characterized. The detector material is based on a heterojunction structure with a barrier that effectively decreases the Shockley-Read-Hall based component of the dark current. A very effective passivation method has been used which successfully inhibits all surface leakage currents. The barrier structure has a 50 % cutoff at 5 µm and 65 % quantum efficiency without antireflective coating. The dark current density is 3×10^-6 A/cm² at -0.05 V bias and 120 K. The optical cavity of the detector has been optimized for maximum capture of available light in the MWIR window. A focal plane array with 640 by 512 pixels and 15 µm pitch was processed based on this barrier structure. High-quality imagery in a system with high F-number will be presented.

Bulk unrelaxed InAsSb alloys with Sb compositions up to 44 % and layer thicknesses up to 3 µm were grown by molecular beam epitaxy. The alloys showed photoluminescence (PL) energies as low as 0.12 eV at T = 13 K. The electroluminescence and quantum efficiency data demonstrated with unoptimized barrier heterostructures at T= 80 and 150 K suggested large absorption and carrier lifetimes sufficient for the development of long wave infrared detectors and emitters with high quantum efficiency. The minority hole transport was found to be adequate for development of the detectors and emitters with large active layer thickness.

Bulk 4" GaSb crystal growth methods based on the Czochralski technique are detailed which deliver highly mono-crystalline substrates that are characterized by low dislocation densities. The latest developments in epitaxy-ready surface finishing will be described and results presented for 4” GaSb substrates processed on a large format, commercial multiwafer polishing platform. Bulk material quality assessments will be made and the surface condition of bare substrates and epitaxial material grown on top of 4" GaSb substrates will be assessed by various surface analytical techniques. We will comment on the available production capacity for 4" GaSb and remark on the scaling challenges that will be required to support the anticipated increase in demand for large diameter GaSb substrates.

The GaSb-based family of materials and heterostructures provides rich bandgap engineering possibilities for a variety of infrared (IR) applications. Mid-wave and long-wave IR photodetectors are progressing toward commercial manufacturing applications, but to succeed they must move from research laboratory settings to general semiconductor production and they require larger diameter substrates than the current standard 2-inch and 3-inch GaSb. Substrate vendors are beginning production of 4-inch GaSb, but another alternative is growth on 6-inch GaAs substrates with appropriate metamorphic buffer layers. We have grown generic MWIR nBn photodetectors on large diameter, 6-inch GaAs substrates by molecular beam epitaxy. Multiple metamorphic buffer architectures, including bulk GaSb nucleation, AlAsSb superlattices, and graded GaAsSb and InAlSb ternary alloys, were employed to bridge the 7.8% mismatch gap from the GaAs substrates to the GaSb-based epilayers at 6.1 Å lattice-constant and beyond. Reaching ~6.2 Å extends the nBn cutoff wavelength from 4.2 to <5 µm, thus broadening the application space. The metamorphic nBn epiwafers demonstrated unique surface morphologies and crystal properties, as revealed by AFM, high-resolution XRD, and cross-section TEM. GaSb nucleation resulted in island-like surface morphology while graded ternary buffers resulted in cross-hatched surface morphology, with low root-mean-square roughness values of ~10 Å obtained. XRD determined dislocation densities as low as 2 × 10⁷ cm^-2. Device mesas were fabricated and dark currents of 1 × 10^-6 A/cm² at 150K were measured. This work demonstrates a promising path to satisfy the increasing demand for even larger area focal plane array detectors in a commercial production environment.

We report ternary growth studies to develop a largely strained InAs/InGaSb superlattice (SL) material for very long wavelength infrared (VLWIR) detection. We select a SL structure of 47.0 Å InAs/21.5 Å In_0.25Ga_0.75Sb that theoretically designed for the greatest possible detectivity, and tune growth conditions for the best possible material quality. Since material quality of grown SLs is largely influenced by extrinsic defects such as nonradiative recombination centers and residual background dopings in the grown layers, we investigate the effect of growth temperature (T_g) on the spectral responses and charge carrier transports using photoconductivity and temperature-dependent Hall effect measurements. Results indicate that molecular beam epitaxy (MBE) growth process we developed produces a consistent gap near 50 meV within a range of few meV, but SL spectral sensing determined by photoresponse (PR) intensity is very sensitive to the minor changes in T_g. For the SLs grown from 390 to 470 °C, a PR signal gradually increases as T_g increases from 400 to 440 °C by reaching a maximum at 440 °C. Outside this growth window, the SL quality deteriorates very rapidly. All SLs grown for this study were n-type, but the mobility varied in a variety of range between 11,300 and 21 cm²/Vs. The mobility of the SL grown at 440 °C was approximately 10,000 V/cm² with a sheet carrier concentration of 5 × 10¹¹ cm^-2, but the mobility precipitously dropped to 21 cm²/Vs at higher temperatures. Using the knowledge we learned from this growth set, other growth parameters for the MBE ternary SL growth should be further adjusted in order to achieve high performance of InAs/InGaSb materials suitable for VLWIR detection.

We report on the development of InAs/AlSb/GaSb based N-structure superlattice pin photodiode. In this new design, AlSb layer in between InAs and GaSb layers acts as an electron barrier that pushes electron and hole wave functions towards the GaSb/InAs interface to perform strong overlap under reverse bias. Experimental results show that, with only 20 periods of intrinsic layers, dark current density and dynamic resistance at -50 mV bias are measured as 6x10^-3 A/cm² and 148 Ωcm² at 77K, respectively. Under zero bias, high spectral response of 1.2A/W is obtained at 5 μm with 50% cut-off wavelengths (λ_c) of 6 μm. With this new design, devices with only 146 nm thick i-regions exhibit a quantum efficiency of 42% at 3 μm with front-side illimunation and no anti-reflection coatings.

This paper describes our efforts on the development of low dark current long-wave infrared (LWIR) photodetectors based on type-II InAs/GaSb strained superlattices. By adopting a so-called pBiBn structure, a hybrid between the conventional PIN structure and unipolar barrier concepts, suppressed dark current and near-zero-bias operation are obtained, respectively. The LWIR photodetector has a dark current density as low as 1.42×10^-5 A/cm² at -60 mV, and R₀A of 5365 Ωcm² at 76 K. The measured peak detectivity at 10.2 µm of 8.7×10¹⁰ cmHz^1/2W^-1 is obtained at -60 mV at 76 K. To further improve the device performances, a newer design with longer cut-off wavelength targeted for near zero-bias was also realized. This 2-µm-thick device exhibits a quantum efficiency of 20% at 10 µm under zero-bias.

We present the development status of Type II superlattice (T2SL) infrared detector in JAXA. Since 2009, we have started a basic research on InAs/GaSb T2SL infrared detectors. Our final goal is to realize the T2SL array detector having a cutoff wave length of λc=15 μm. In order to confirm a technical feasibility of 15 μm cutoff T2SL detector, we fabricated T2SL samples having a different thickness of InAs/ 7 monolayers (ML) GaSb. These crystals are designed for the cutoff wavelength from 6 μm to 15 μm. The X-ray Diffraction measurement shows a mismatch between the substrate and superlattice layers is below 0.006%. The surface morphology of the samples with an atomic force microscope is 1.5-3.3 Å RMS for 5×5 μm square regions. We also fabricated single pixel detectors with these crystals. We show the results of the spectral response measurement using a FTIR system. We also show the development status of an array detector. The array detector having the cutoff wavelength of 6 μm is successfully demonstrated. However, further improvements are required for a future 15 μm cutoff array detector.

A wavelength selective wideband uncooled infrared (IR) sensor that detects middle-wavelength and long-wavelength infrared (MWIR and LWIR) regions has been developed using a two-dimensional plasmonic absorber (2D PLA). The 2D PLA has a Au-based 2D periodic hole-array structure, where photons can be manipulated using the surface plasmonlike mode. Numerical investigations demonstrate that the wavelength of the absorption can be designed according to the surface period of holes over a wide wavelength range (MWIR and LWIR regions). A microelectromechanical system (MEMS)-based uncooled IR sensor with a 2D PLA was fabricated using complementary metal oxide semiconductor (CMOS) and micromachining techniques. The 2D PLA was formed from a Au layer sputtered on a perforated oxide layer. A reflection layer was introduced to the backside of the 2D PLA to prevent additional absorption. Measurement of the spectral responsivity shows that selective enhancement of responsivity is achieved over both MWIR and LWIR regions, where the wavelength of the responsivity peak coincides with the hole period of the 2D PLA. The results obtained here provide direct evidence that a wideband wavelength selective IR sensor can be realized simply by design of the 2D PLA surface structure without the need for vertical control in terms of gap or thickness. A pixel array where each pixel has a different detection wavelength would be developed for multicolor infrared imaging using standard CMOS and micromachining techniques.

A dual-band microbolometer with separate absorption of each wavelength band would be desirable for multispectral applications. In addition, a three dimensional (3D) stacked structure would be advantageous for size and integration in focal plane arrays. We present designs for a 3D stacked dual-band microbolometer based on the in-band and out-of-band reflection and transmission characteristics of resistive dipoles and slots. The mechanism of individual absorption in each layer of a dual-band microbolometer is analyzed and simulated to allow the resistive slot layer to efficiently absorb the LWIR band while a superposed resistive dipole layer absorbs the MWIR band. The top dipole layer is designed to have peak absorption at 5 μm, with a second underlying slot layer and mirror layer designed to have peak absorption at 10 μm. The stacked combination of two different types of layers provides highly efficient wavelength selective absorption, yielding calculated power absorption efficiency of nearly 100 % for both LWIR and MWIR bands.

An uncooled microbolometer with peak responsivity in the long wave infrared region of the electromagnetic radiation is developed at Sensonor AS. It is a 384 x 288 focal plane array with a pixel pitch of 25µm, based on monocrystalline Si/SiGe quantum wells as IR sensitive material. The high sensitivity (TCR) and low 1/f-noise are the main performance characteristics of the product. The frame rate is maximum 60Hz and the output interface is digital (LVDS). The quantum well thermistor material is transferred to the read-out integrated circuit (ROIC) by direct wafer bonding. The ROIC wafer containing the released pixels is bonded in vacuum with a silicon cap wafer, providing hermetic encapsulation at low cost. The resulting wafer stack is mounted in a standard ceramic package. In this paper the architecture of the pixels and the ROIC, the wafer packaging and the electro-optical measurement results are presented.

Metal-Oxide-Metal diodes offer the possibility of directly rectifying infrared radiation. To be effective for sensing or energy harvesting they must be coupled to an antenna which produces intense fields at the diode. While antennas significantly increase the effective capture area of the MOM diode, it is still limited and maximizing the captured energy is still a challenging goal. In this work we investigate integrating MOM diodes with a slot antenna Frequency Selective Surface (FSS). This maximizes the electromagnetic capture area while minimizing the transmission line length which helps reduce losses because metal losses are much lower at DC than at infrared frequencies. Our design takes advantage of a single self-aligned patterning step using shadow evaporation. The structure is optimized at 10.6 µm to have less than 2% reflection (polarization sensitive) and simulations predict that 70% of the incident energy is dissipated into the oxide layer. Initial experimental results fabricated with e-beam lithography are presented and the diode coupled FSS is shown to produce a polarization sensitive unbiased DC short circuit current. This work is promising for both infrared sensing and imaging as well as direct conversion of thermal energy.

We experimentally demonstrate a structured thin film that selectively absorbs incident electromagnetic waves in discrete bands, which by design occur in any chosen range from near UV to far infrared. The structure consists of conducting islands separated from a conducting plane by a dielectric layer. By changing dimensions and materials, we have achieved broad absorption resonances centered at 0.36, 1.1, 14, and 53 microns wavelength. Angle-dependent specular reflectivity spectra are measured using UV-visible or Fourier spectrometers. The peak absorption ranges from 85 to 98%. The absorption resonances are explained using the model of an LCR resonant circuit created by coupling between dipolar plasma resonance in the surface structures and their image dipoles in the ground plane. The resonance wavelength is proportional to the dielectric permittivity and to the linear dimension of the surface structures. These absorbers have application to thermal detectors of electromagnetic radiation.

This paper introduces a method of broadband absorption enhancement that can be integrated with the conventional suspended microbolometer process with no significant additional cost. The premise of this study is that electric field can be enhanced throughout the structural layer of the microbolometer, resulting in an increase in the absorption of the infrared radiation in the long wave infrared window. A concentric double C-shaped plasmonic geometry is simulated using the FDTD method, and this geometry is fabricated on suspended pixel arrays. Simulation results and FTIR measurements are in good agreement indicating a broadband absorption enhancement in the 8 µm-12 µm range for LWIR applications. The enhancement is attained using metallic geometries embedded in the structural layer of the suspended microbridge, where the metallic-dielectric interface increases the average absorption of a 35 µm pixel from 67.6% to 80.1%.

During his distinguished 37-year career as a research physicist at the Honeywell Research Center in Minneapolis, Minnesota, Dr. Paul W. Kruse (1927-2012) played leadership roles in two disruptive infrared detector technologies, the narrow-gap semiconductor alloy HgCdTe and the silicon CMOS-based microbolometer array, both of which revolutionized the worldwide infrared detector industry. He served on numerous government advisory boards and panels, including the Army Scientific Advisory Panel and the Army Science Board, for which he received the Outstanding Civilian Service Medal. After retiring for Honeywell in 1993, he remained active in the infrared detector field in several roles: as a successful small-business entrepreneur, as an author of two books, and as a SPIE lecturer. His books, papers and lectures have educated new generations of workers in the infrared detector industry. His career, a model for industrial research physicists, has had major and permanent impacts on the worldwide infrared detector industry. This paper is a summary of the career of Paul W. Kruse, as well as a tribute to that career and its lasting legacy.

Uncooled infrared detectors with 12μm pixel pitch video graphics array (VGA) have been developed. To improve the signal to noise ratio (SNR) for 12μm pixel pitch, a highly sensitive bolometer material, an advanced pixel structure for thermal isolation and a newly designed read-out IC (ROIC) have been also developed. The bolometer material has been improved by using vanadium niobate. Over a wide range of temperature, temperature coefficient of resistance (TCR) is achieved higher level than -3.6%/K, which is 2 times higher than that for the conventional bolometer material. For thermal isolation, thermal conductance (Gth) value for the new pixel structure, fabricated by using triple level sacrificial layer process, is estimated to be 5nW/K, which is 1/5 times lower than that for the conventional pixel structure. On the other hand, since the imaging area is reduced by the pixel pitch, the uniformity of pixel can be improved. This enables to remove the non-uniformity correction (NUC) circuit in the ROIC. Removal of this circuit is effective for low power and low noise. This 12μm pixel pitch VGA detector is packaged in a compact (24 × 24 × 6.5 mm) and lightweight (11g) ceramic package. In addition, it has been incorporated in a newly developed prototype miniature imager. The miniature imager has dimension of 25(H) ×25(W) ×28(L) mm and weight of 30g. This imager is compact and small enough to fit in your hand. Hereafter, this imager is greatly expected to be applied to mobile systems.

Long range sights and targeting systems require a combination of high spatial resolution, low temporal NETD, and wide field of view. For practical electro-optical systems it is hard to support these constraints simultaneously. Moreover, achieving these needs with the relatively low-cost Uncooled μ-Bolometer technology is a major challenge in the design and implementation of both the bolometer pixel and the Readout Integrated Circuit (ROIC). In this work we present measured results from a new, large format (1024×768) detector array, with 17μm pitch. This detector meets the demands of a typical armored vehicle sight with its high resolution and large format, together with low NETD of better than 35mK (at F/1, 30Hz). We estimate a Recognition Range for a NATO target of better than 4 km at all relevant atmospheric conditions, which is better than standard 2nd generation scanning array cooled detector. A new design of the detector package enables improved stability of the Non-Uniformity Correction (NUC) to environmental temperature drifts.

We have developed a low-cost uncooled infrared radiation focal plane array (FPA) requiring no thermoelectric cooler (TEC), which has 320 x 240 detection pixels with 22 um pitch. The silicon single-crystal series p-n junction diodes and the low-noise readout circuit on the same SOI wafer fabricated by 0.13 um CMOS technology were utilized for infrared (IR) detection. The temperature dependence in the readout circuit was eliminated by correlated double sampling (CDS) operation with reference pixel that was insensitive to infrared radiation. In order to reduce the temperature dependence, we improved the reference pixel and the readout circuit. Although the reference pixels should be completely insensitive to IR radiation, prior reference pixels showed measurable sensitivity. The improved reference pixel was formed by partially releasing with bulk-micromachining and was verified to be insensitive to IR radiation by an object of 400°C. The readout circuit had a differential amplifier instead of a singletransistor amplifier and an analog-to-digital converter (ADC). In each portion, CDS was applied to reduce temperature dependence. The first CDS operation was used for eliminating the pixel output variation and the second operation was used for canceling the variation of the differential amplifier. The output variation referred to input was reduced to 1/30 compared with that of the prior circuit. Moreover, the residual variation of output voltage was reduced by CDS operation in ADC and stable output data was obtained with ambient temperature variation. With these improvements, the sensitivity variation of the FPA was improved to 10% in the range of -30 degrees to 80 degrees and noise equivalent temperature difference (NETD) of 40 mK was achieved.

Seventeen (17) µm pixel Long Wave Infrared (LWIR) Sensors based on vanadium oxide (VO_x) micro-bolometers have been in full rate production at BAE Systems’ Night Vision Sensors facility in Lexington, MA for the past five years.[1] We introduce here a commercial camera core product, the Airia-M^TM imaging module, in a VGA format that reads out in 30 and 60Hz progressive modes. The camera core is architected to conserve power with all digital interfaces from the readout integrated circuit through video output. The architecture enables a variety of input/output interfaces including Camera Link, USB 2.0, micro-display drivers and optional RS-170 analog output supporting legacy systems. The modular board architecture of the electronics facilitates hardware upgrades allow us to capitalize on the latest high performance low power electronics developed for the mobile phones. Software and firmware is field upgradeable through a USB 2.0 port. The USB port also gives users access to up to 100 digitally stored (lossless) images.

The DRS Tamarisk® ₃₂₀ camera, introduced in 2011, is a low cost commercial camera based on the 17 µm pixel pitch 320×240 VOx microbolometer technology. A higher resolution 17 µm pixel pitch 640×480 Tamarisk®₆₄₀ has also been developed and is now in production serving the commercial markets. Recently, under the DARPA sponsored Low Cost Thermal Imager-Manufacturing (LCTI-M) program and internal project, DRS is leading a team of industrial experts from FiveFocal, RTI International and MEMSCAP to develop a small form factor uncooled infrared camera for the military and commercial markets. The objective of the DARPA LCTI-M program is to develop a low SWaP camera (<3.5 cm³ in volume and <500 mW in power consumption) that costs less than US $500 based on a 10,000 units per month production rate. To meet this challenge, DRS is developing several innovative technologies including a small pixel pitch 640×512 VOx uncooled detector, an advanced digital ROIC and low power miniature camera electronics. In addition, DRS and its partners are developing innovative manufacturing processes to reduce production cycle time and costs including wafer scale optic and vacuum packaging manufacturing and a 3-dimensional integrated camera assembly. This paper provides an overview of the DRS Tamarisk® project and LCTI-M related uncooled technology development activities. Highlights of recent progress and challenges will also be discussed. It should be noted that BAE Systems and Raytheon Vision Systems are also participants of the DARPA LCTI-M program.

In this work a breakthrough in the field of low cost uncooled infrared detectors is presented: an 80x80 MWIR VPD PbSe detector monolithically integrated with the corresponding Si-CMOS circuitry. Fast speed of response and high frame rates are, until date, non existing performances in the domain of low cost uncooled IR imagers. The new detector presented fills the gap. The device is capable to provide MWIR images to rates as high as 2 KHz, full frame, in real uncooled operation which converts it in an excellent solution for being used in applications where short events and fast transients dominate the system dynamics to be studied or detected. VPD PbSe technology is unique because combines all the main requirements demanded for a volume ready technology: 1. Simple processing 2. Good reproducibility and homogeneity 3. Processing compatible with big areas substrates 4. Si-CMOS compatible (no hybridation needed) 5. Low cost optics and packagin The new FPA represents a milestone in the road towards affordable uncooled MWIR imagers and it is the demonstration of VPD PbSe technology has reached industrial maturity. The device presented in the work was processed on 8-inch Si wafers with excellent results in terms of manufacturing yield and repeatability. The technology opens the MWIR band to SWaP concept.

Penetration of uncooled (room temperature operation) thermal detector arrays into high volume commercial products depends on very low cost technology linked to high volume production. A series of innovative and revolutionary developments is now allowing arrays based on bulk pyroelectric ceramic material to enter the consumer marketplace providing everything from sophisticated security and people monitoring devices to hand held thermal imagers and visual IR thermometers for preventative maintenance and building inspection. Although uncooled resistive microbolometer detector technology has captured market share in higher cost thermal imager products we describe a pyroelectric ceramic technology which does not need micro electro-mechanical systems (MEMS) technology and vacuum packaging to give good performance. This is a breakthrough for very low cost sensors and imagers. Recent developments in a variety of products based on pyroelectric ceramic arrays are described and their performance and applicability compared and contrasted with competing technologies.

This paper presents a 32x32 microbolometer thermal imaging sensor for human body temperature measurement. Waferlevel vacuum packaging technology allows us to get a low cost and compact imaging sensor chip. The microbolometer uses V-W-O film as sensing material and ROIC has been designed 0.35-um CMOS process in UMC. A thermal image of a human face and a hand using f/1 lens convinces that it has a potential of human body temperature for commercial use.

Nickel oxide (NiO) film was formed on the SiO₂/Si substrate at the room temperature with water cooling system by reactive RF sputter. The feasibility of bolometric material was investigated, and a microbolometer using the NiO film was fabricated and evaluated. The NiO films were analyzed by using grazing-incidence X-ray diffraction (GIXRD). The NiO(111), NiO (200), and NiO (220) peaks expected as the main spectrum were dominantly appeared on the polycrystalline NiO films. The representative resistivity acquired at the O₂/(Ar+O₂) ratio of 10% sample was about 40.6 Ωcm. The resistivity of 40.6 Ωcm obtained in low oxygen partial pressure was inclined to reduce to 18.65 Ωcm according to the increase of the O₂/(Ar+O₂) ratio. The TCR value of fabricated microbolometer was −1.67%/℃ at the NiO film resistivity of 40.6 Ωcm. The characteristics of fabricated NiO film and microbolometer were demonstrated by XRD patterns, TCR value, and SEM image.

This paper presents a systematic study of the 1/f noise coefficient as a function of pixel geometry for microbolometer structures. Structures with various VO_x widths, electrode gaps, electrode widths and via hole sizes were fabricated and characterized. The experimental results show that the 1/f noise coefficient is adversely affected by current non uniformity, in agreement with model predictions. Design parameters that significantly impact current non uniformity are identified and approaches to minimize their importance are proposed.

Presented is an uncooled surface-micromachined thermoelectric (TE) infrared detector that features P-doped and N-doped polysilicon wires as the thermocouple pair and an umbrella like optical cavity as the absorber to achieve a high fill factor. A responsivity as high as1800V/W @5Hz and a response time of smaller than ~10ms are measured in vacuum when viewing a 500K blackbody with no concentrating optics at room temperature. The reported responsivity is more than 10 times higher than the value reported earlier [1] from similar structures due to the improvement in the thermoelectric coefficient and the thermal isolation of the cell. Finite Element Analysis is used to predict the detector’s performance and the results are in a good agreement with the measurements. The dominant source of noise is also investigated in these thermoelectric IR detectors and it is believed to be Johnson noise when they are operated under an open circuit condition. The fabricated detectors have resistances in the range of 20 to 70KOhm resulting in a Johnson noise of about 20 to 36 nV/Hz^0.5. The specific detectivity (D*) is calculated to be higher than 10^8cmHz^0.5/W. To the best of our knowledge, this is the highest reported D* for such small thermoelectric IR sensors. The measured NETD is 120mK with an f/1.5 lens.

Over the past few years, a new type of High Operating Temperature (HOT) photon detector has been developed at SCD, which operates in the blue part of the MWIR window of the atmosphere (3.4-4.2 μm). This window is generally more transparent than the red part of the MWIR window (4.4-4.9 μm), especially for mid and long range applications. The detector has an InAsSb active layer, and is based on the new "XBn" device concept. We have analyzed various electrooptical systems at different atmospheric temperatures, based on XBn-InAsSb operating at 150K and epi-InSb at 95K, respectively, and find that the typical recognition ranges of both detector technologies are similar. Therefore, for very many applications there is no disadvantage to using XBn-InAsSb instead of InSb. On the other hand XBn technology confers many advantages, particularly in low Size, Weight and Power (SWaP) and in the high reliability of the cooler and Integrated Detector Cooler Assembly (IDCA). In this work we present a new IDCA, designed for 150K operation. The 15 μm pitch 640×512 digital FPA is housed in a robust, light-weight, miniaturised Dewar, attached to Ricor's K562S Stirling cycle cooler. The complete IDCA has a diameter of 28 mm, length of 80 mm and weight of < 300 gm. The total IDCA power consumption is ~ 3W at a 60Hz frame rate, including an external miniature proximity card attached to the outside of the Dewar. We describe some of the key performance parameters of the new detector, including its NETD, RNU and operability, pixel cross-talk, and early stage yield results from our production line.

Over the last several years, owing to the implementation of advanced device architectures, antimony-based type-II superlattice (T2-SL) infrared (IR) photodetectors and their focal plane arrays (FPAs) have achieved significant advancements. Here we present our recent effort towards the development of high operating temperature (HOT) mid-IR (MWIR) photodetectors, which utilizes an interband cascade scheme with discrete InAs/GaSb SL absorbers, sandwiched between electron and hole barriers. This low-noise device architecture has enabled background-limited operation above 150 K (300 K, 2π field-of-view), as well as above room temperature response in the mid-IR region. The detector yields a dark current density of 1.10×10^-7 A/cm² (1.44×10^-3 A/cm²) at -5 mV, and a Johnson-limited D* of 2.22×10¹¹ cmHz^1/2/W (1.58×10⁹ cmHz^1/2/W) at 150 K (room temperature) and 3.6 μm, respectively. In this presentation, we will discuss the operation principles of the interband cascade design and our most recent progress in MWIR photodetectors toward high operating temperatures.

We describe our recent efforts in developing visible to mid-wave (0.5 µm to 5.0 µm) broadband photon-trap InAsSb-based infrared detectors grown on GaAs substrates operating at high temperature (150-200K) with low dark current and high quantum efficiency. Utilizing an InAsSb absorber on GaAs substrates instead of an HgCdTe absorber will enable low-cost fabrication of large-format, high operating temperature focal plane arrays. We have utilized a novel detector design based-on pyramidal photon trapping InAsSb structures in conjunction with compound barrier-based device architecture to suppress both G-R dark current, as well as diffusion current through absorber volume reduction. Our optical simulation show that our engineered pyramid structures minimize the surface reflection compared to conventional diode structures acting as a broadband anti-reflective coating (AR). In addition, it exhibits > 70-80% absorption over the entire 0.5 µm to 5.0 µm spectral range while providing up to 3× reduction in absorber volume. Lattice-mismatched InAs_0.82Sb_0.18 with 5.25 µm cutoff at 200K was grown on GaAs substrates. 128×128/60μm and 1024×1024/18μm detector arrays that consist of bulk absorber as well as photon-trap pyramid structures were fabricated to compare the detector performance. The measured dark current density for the diodes with the pyramidal absorber was 3× lower that for the conventional diode with the bulk absorber, which is consistent with the volume reduction due to the creation of the pyramidal absorber topology. We have achieved high D* (< 1.0 x 10¹⁰ cm √Hz/W) and maintain very high (< 80 %) internal quantum efficiency over the entire band 0.5 to 5 µm spectral band at 200K.

Mid-wavelength infrared (MWIR) InAsSb alloy barrier detectors grown on GaAs substrates were characterized as a function of temperature to evaluate their performance. Detector arrays were fabricated in a 1024 × 1024 format on an 18 μm pitch. A fanout was utilized to directly acquire data from a set of selected detectors without an intervening read out integrating circuit (ROIC). The detectors have a cutoff wavelength equal to ~ 4.9 μm at 150 K. The peak internal quantum efficiency (QE) required a reverse bias voltage of 1 V. The detectors were diffusion-limited at the bias required to attain peak QE. Multiple 18 μm × 18 μm detectors were tied together in parallel by connecting the indium bump of each detector to a single large metal pad on the fanout. The dark current density at -1 V bias for a set of 64 × 64 and 6 × 6 array of detectors, each of which were tied together in parallel was ~ 10^-3 A/cm² at 200 K and 5 × 10^-6 A/cm² at 150 K. The 4096 (64 × 64) and 36 (6 × 6) detectors, both have similar J_dark vs V_d characteristics, demonstrating high operability and uniformity of the detectors in the array. The external QE measured using a narrow band filter centered at ~ 4 μm had values in the 65 – 70 % range. Since the detectors were illuminated through a GaAs substrate which has a reflectance of 29%, the internal QE is greater than 90 %. A 1024 × 1024 ROIC on an 18 μm pitch was also designed and fabricated to interface with the barrier detectors. QE at 150 K for a 1024 × 1024 detector array hybridized to a ROIC matched the QE measured on detectors that were measured directly through a fanout chip. Median D* at 150 K under a flux of 1.07 × 10¹⁵ ph/(cm²/s was 1.0 x 10¹¹ cm Hz^1/2 /W.

We report a bias selectable dual-band Type-II superlattice-based short-wave infrared (SWIR) and mid-wave infrared (MWIR) co-located photodetector capable of active and passive imaging. A new double-layer etch-stop scheme is introduced for back-side-illuminated photodetectors, which enhanced the external quantum efficiency both in the SWIR and MWIR spectral regions. Temperature-dependent dark current measurements of pixel-sized 27 μm detectors found the dark current density to be ~1×10^-5 A/cm² for the ∼4.2 μm cut-off MWIR channel at 140 K. This corresponded to a reasonable imager noise equivalent difference in temperature of ∼49 mK using F⁄2.3 optics and a 10 ms integration time (tint), which lowered to ∼13 mK at 110 K using and integration time of 30 ms, illustrating the potential for high-temperature operation. The SWIR channel was found to be limited by readout noise below 150 K. An excellent imagery from the dual-band imager exemplifying pixel coincidence is shown.

InAsSb ternary alloy is potentially capable of operating at the longest cut-off wavelength (about 9 μm at 77 K) in the entire III-V family. Recently, there has been a considerable progress in development of the InAsSb focal plane arrays. The high operation temperature conditions were successfully achieved with A^IIIB^V unipolar barrier structures including InAsSb/AlAsSb material system. In this paper, the performance of medium wavelength infrared (MWIR) InAsSb-based nBnnn+ detectors, called also "bariodes", is examined theoretically taking into account thermal generation governed by the Auger and radiative mechanisms. In our model, the heterojunction barrier-active region (absorber) is assumed to be decisive as the contributing dark current mechanism limiting detector's performance. Since there is no depletion layer in the active layer of such devices, generation-recombination and trap assisted tunneling mechanisms are suppressed leading to lower dark currents in bariode detectors in comparison to standard diodes. Detailed analysis of the detector’s performance (such as dark current, RA product, and current responsivity) versus bias voltage and operating temperatures are performed pointing out optimal working conditions. The theoretical predictions of bariode parameters are compared with experimental data published in the literature. Finally, the bariode performance is compared with standard p⁺-on-n InAsSb photodiodes operated at room temperature with the same bandgap wavelength.

This paper presents one-dimensional numerical simulations and analytical modeling of ideal (only diffusion current and only Auger-1 and radiative recombination) InAs nBn detectors having n-type barrier layers, with donor concentrations ranging from 1.8×10¹⁵ to 2.5×10¹⁶ cm^-3. We examine quantitatively the three space charge regions in the nBn detector with an n-type barrier layer (BL), and determine criteria for combinations of bias voltage and BL donor concentration that allow operation of the nBn with no depletion region in the narrow-gap absorber layer (AL) or contact layer (CL). We determine the quantitative characteristics of the valence band barrier that is present for an n-type BL. From solution of Poisson’s equation in the uniformly doped BL, we derive analytical expressions for the valence band barrier heights versus bias voltage for holes in both the AL and the CL. These expressions show that the VB barrier height varies linearly with the BL donor concentration and as the square of the BL width. Using these expressions, we constructed a phenomenological equation for the dark current density versus bias voltage which agrees reasonably well with the shape of the J(V) curves from numerical simulations. Our simulations suggest that the nBn detector should be able to be operated at or near zero-bias voltage.

An infrared (IR) transparent window is necessary for the IR sensor package. The most commonly used materials for IR transparent window are germanium (Ge) and silicon (Si). Ge has excellent optical properties but also the disadvantage of expensive price. Si has merits such as inexpensive cost and CMOS process compatibility but it has lower transmittance in the range of LWIR region than Ge. Therefore, an alternative anti-reflection (AR) coating is necessary to increase the transmittance of Si as an IR transparent window in the LWIR region. A simple single layer antireflection coating was newly designed on the silicon window for the infrared sensor package. Among the various materials, nickel oxide (NiO) was selected as an AR coating material due to its suitable optical properties and simple process. NiO film was deposited onto the double sided polished Si wafer by reactive rf sputtering with Ni target in an environment of Ar and O₂ mixed gas. The thickness of the NiO film was determined by Essential Macleod simulation. FT-IR was used to measure the transmittance of the samples in the LWIR region. After the nickel oxide film was sputtered onto the double sides of the silicon wafer, the measured transmittance of the Si wafer was increased over 20% in the LWIR region compared with that of uncoated Si wafer. Additionally, annealing effect on the transmittance of NiO coated Si wafer was studied. By increasing the annealing temperature from 300° to 700°, an additional increase of transmittance was achieved.

Hybrid diamondlike carbon (h-DLC) coatings for multispectral use combine the hardness of protective DLC coatings with the multispectral functionality of high-end IR coatings.

Dual-band infrared camera systems allow viewing and comparison of the 3-5µ and 8-12µ spectrum regions, improve visibility at sunrise/sunset and help distinguish between targets and decoys. They also enhance the ability to defeat many IR countermeasures such as smoke, camouflage and flares. As dual band 3rd generation FLIR systems progress, we introduce coatings for these systems. This paper describes advanced dual band coatings for the 3-5µ and 8-12µ spectrum regions, with reference to single band coatings. Theoretical and measured designs are shown for ZnSe, ZnS, Ge and IG-6 substrates. Triple band AR coatings with additional transmittance at 1.06µ are also demonstrated.

The military uncooled infrared market is driven by the continued cost reduction of the focal plane arrays whilst maintaining high standards of sensitivity and steering towards smaller pixel sizes. As a consequence, new optical solutions are called for. Two approaches can come into play: the bottom up option consists in allocating improvements to each contributor and the top down process rather relies on an overall optimization of the complete image channel. The University of Rennes I with Thales Angénieux alongside has been working over the past decade through French MOD funding’s, on low cost alternatives of infrared materials based upon chalcogenide glasses. A special care has been laid on the enhancement of their mechanical properties and their ability to be moulded according to complex shapes. New manufacturing means developments capable of better yields for the raw materials will be addressed, too. Beyond the mere lenses budget cuts, a wave front coding process can ease a global optimization. This technic gives a way of relaxing optical constraints or upgrading thermal device performances through an increase of the focus depths and desensitization against temperature drifts: it combines image processing and the use of smart optical components. Thales achievements in such topics will be enlightened and the trade-off between image quality correction levels and low consumption/ real time processing, as might be required in hand-free night vision devices, will be emphasized. It is worth mentioning that both approaches are deeply leaning on each other.

In the 8-12 micron waveband Focal Plane Arrays (FPA) are available with a pixel pitch of 12 microns or less. High resolution FPAs with VGA, XGA and SXGA resolution should become available at a reasonable price. These will require new lens designs to give the required fields of view. The challenge for the Optical Designer is to design lenses when the pixel pitch of the detector is the same as the wavelength of the light imaged. The lens specification will need to give more thought to the resolution required by the system. A smaller pixel pitch detector defines a requirement for a shorter focal length to give the same field of view. This will have a number of effects upon the lens design. Geometrical aberrations decrease proportionally with the focal length. Reverse telephoto layouts will become more common, particularly when the system has a shutter. The increase in pixel count will require wide field of view lenses which present particular challenges. The impact of diffraction effects on the lens design is considerably increased. The fast F-number causes an increase in the diffraction limit of the system, but also increases geometric aberrations by a cube law. Therefore the balance between the diffraction limited and the aberration limited performance becomes more difficult. The first approach of the designer is to re-use proven designs originally intended for use with 17micron detectors. Some of these designs will have adequate performance at the Nyquist limit of the 12 micron detectors. Even smaller detector pitches, such as 10 micron, will demand new approaches to Infra Red lens design. The traditional approach will quickly increase the number of elements to 3 or even more. This could lead to the lenses with medium fields of view driving the system cost. A close cooperation between the camera developer and lens designer will become necessary in order to explore alternate approaches, such as wavefront coding, in order to reach the most cost effective solution.

The development and implementation of wafer level packaging for commercial microbolometers has opened the pathway towards full wafer-based thermal imaging systems. The next challenge in development is moving from discrete element LWIR imaging systems to a wafer based optical system, similar to lens assemblies found in cell phone cameras. This paper will compare a typical high volume thermal imaging design manufactured from discrete lens elements to a similar design optimized for manufacture through a wafer based approach. We will explore both performance and cost tradeoffs as well as review the manufacturability of all designs.

Recent developments in the Mid Wave InfraRed (MWIR) optical domain were made on materials, optical design and manufacturing. They answer increasing demands for more compact, less temperature dependent optical systems with increased optical performances and complexity (multi- or hyper- spectral imagery). At the same time, the characterization of these components has become strategic and requires solutions with higher performance. The optical quality of such devices is measured by wave front sensing techniques. PHASICS previously developed wave front sensors based on Quadri-Wave Lateral Shearing Interferometry (QWLSI) using broadband microbolometers cameras for infrared measurements. However they suffer from reduced light sensitivity in the MWIR domain, which limits their use with broadband sources such as black bodies. To meet metrology demands, we developed an innovative wave front sensor. This instrument combines the metrological qualities of QWLSI with the radiometric performances of a last generation detection block (Infrared Detector Dewar Cooler Assembly, IDDCA) with a quantum infrared focal plane array (IRFPA) of HgCdTe technology. The key component of QWLSI is a specific diffractive grating placed a few millimeters from the focal plane array. This requirement implies that this optics should be integrated inside the IDDCA. To achieve this, we take advantage of the experience acquired from recent developments with optics integrated in IDDCA. Thanks to this approach, we developed a high spatial resolution MWIR wave front sensor (160x128 points) with a high sensitivity for accurate measurements under low-flux conditions. This paper will present the instrument technological solutions, the development key steps and experimental results on various metrology applications.

We present a compact infrared cryogenic multichannel camera with a wide field of view equal to 120°. By merging the optics with the detector, the concept has to be compatible with both cryogenic constraints and wafer-level fabrication. For this, we take advantage of the progress in micro-optics to design a multichannel optical architecture directly integrated on the detector. This wafer-level camera uses state of art microlenses with a high sag height. The additional mass of the optics is sufficiently small to be compatible with the cryogenic environment of the Dewar. The performance of this camera will be discussed. Its characterization has been carried out in terms of modulation transfer function and noise equivalent temperature difference (NETD). The optical system is limited by the diffraction. By cooling the optics, we achieve a very low NETD equal to 15 mK compared with traditional infrared cameras. A postprocessing algorithm that aims at reconstructing a well-sampled image from the set of undersampled raw subimages produced by the camera is proposed and validated on experimental images.

We report new multispectral materials that transmit from 0.9 to < 12 µm in wavelength. These materials fill up the glass map for multispectral optics and vary in refractive index from 2.38 to 3.17. They show a large spread in dispersion (Abbe number) and offer some unique solutions for multispectral optics designs. One of the glasses developed is a very good candidate to replace Ge, as it has a combination of excellent properties, including high Abbe number in the LWIR, high index of 3.2, 60% lower dn/dT, and better thermal stability at working temperatures. Our results also provide a wider selection of optical materials to enable simpler achromat designs. For example, we have developed other glasses that have relatively high Abbe number in both the MWIR and LWIR regions, while our MILTRAN ceramic has low Abbe number in both regions. This makes for a very good combination of glasses and MILTRAN ceramic (analogous to crown and flint glasses in the visible) for MWIR + LWIR dual band imaging. We have designed preliminary optics for one such imager with f/2.5, 51 mm focal length and 22 degrees FOV using a spaced doublet of NRL's glass and MILTRAN ceramic. NRL's approach reduces the number of elements, weight, complexity and cost compared with the approach using traditional optics. Another important advantage of using NRL glasses in optics design is their negative or very low positive dn/dT, that makes it easier to athermalize the optical system.

Many design approaches to the color correction of infrared optics have evolved from theories based on first-order linear equations. When faced with broad spectral design, however, such technologies can fall short. The use of linear approximations for certain material properties has limited the development of well-corrected lenses when faced with higher order color and aberration correction. In this paper we will discuss broad spectral multi-band imaging with specific emphasis on a fast catadioptric wide-angle system design, highlighting its advantages and disadvantages. The result of this work will illustrate an improved solution yielding a compact well-corrected lens adapted for use in the broadband spectrum.

We describe the benefits to camera system SWaP-C associated with the use of aspheric molded glasses and optical polymers in the design and manufacture of optical components and elements. Both camera objectives and display eyepieces, typical for night vision man-portable EO/IR systems, are explored. We discuss optical trade-offs, system performance, and cost reductions associated with this approach in both visible and non-visible wavebands, specifically NIR and LWIR. Example optical models are presented, studied, and traded using this approach.

Fluorozirconate glasses, such as ZBLAN (ZrF₄-BaF₂-LaF₃-AlF₃-NaF), have the potential for optical transmission from 0.3 μm in the UV to 7 μm in the IR region. However, crystallites formed during the fiber drawing process prevent this glass from achieving its desired transmission range. The temperature at which the glass can be drawn into a fiber is known as the working range, defined as (Tx - Tg), bounded by the glass transition temperature (Tg) and the crystallization temperature (Tx). In contrast to silica glasses, the working temperature range for ZBLAN glass is extremely narrow. Multiple ZBLAN samples were subject to a heating and quenching test apparatus on the parabolic aircraft, under a controlled 0-g and hyper-g environment and compared with 1-g ground tests. The microgravity duration on board Zero-G Corporation parabolic aircraft is approximately 20 seconds and the hyper-g intervals are approximately 56 seconds. Optical microscopy examination elucidates crystal growth in ZBLAN is suppressed when processed in a microgravity environment. The crystallization temperature, Tx, at which crystals form increased, therefore, significantly broadening the working temperature range for ZBLAN.

The imaging quality of assembled optical systems is strongly influenced by the alignment errors of the individual lenses in the assembly. Although instrumentation for characterizing centering errors for the visual spectral range existed for some time, the technology to include the LWIR (8-12µm) and the MWIR (3-5µm) spectral ranges was only recently developed. Here, we report on the development and performance of such a measurement system that is capable of fully characterizing the alignment of all individual elements of an IR lens assembly in a non-contact and non-destructive fashion. The main component of the new instrument is an autocollimator working in the LWIR that determines the position of the center of curvature of each individual IR lens surface with respect to the instruments reference axis. This position data are used to calculate the shift and tilt of the individual lenses with respect to each other or a user-defined reference axis like e.g. the assembly housing. Finally, to complete the whole picture, the thicknesses and air gaps between individual lenses are measured with a low coherence interferometer built into the instrument. In order to obtain precise data, the instrument software takes the measured real centering error into account and directs the user to optimally align the assembly with respect of the interferometer reference axis, which then determines the position of the vertex positions along the optical axis and from these the center thicknesses of each lens and the air gaps between lenses with an accuracy below one micrometer.

High contrast wire grid polarizers on silicon suitable for mid-wavelength infrared (MWIR) and long-wavelength infrared (LWIR) applications have been developed using wafer-scale aluminum nanowire patterning capabilities. The 144 nm pitch MWIR polarizer typically transmits better than 95% of the passing polarization state from 3.5-5.5 microns while maintaining a contrast ratio of better than 37dB. Between 7 and 15 microns, the broadband LWIR polarizer typically transmits between 55 and 90% of the passing state and has a contrast ratio better than 40 dB. A narrowband 10.6 micron polarizer shows about 85% transmission in the passing state and a contrast ratio of 45 dB. Transmission and reflection measurements were made using various FTIR spectrometers and compared to RCWA modeling of the wire grid polarizer (WGP) performance on antireflection-coated wafers. Laser Damage Threshold (LDT) testing was performed using a continuous wave CO₂ laser for the broadband LWIR product and showed a damage threshold of 110 kW/cm₂ in the blocking state and 10 kW/cm₂ in the passing state. The MWIR LDT testing used an OPO operating at 4 microns with 7 ns pulses and showed LDT of 650 W/cm₂ in the blocking state and better than 14 kW/cm₂ in the passing state

An echelle spectrograph can provide high resolving power (wavelength/FWHM) across a broad spectral range. These optical instruments are commonly used in spectroscopy for atomic and molecular identification in astronomical observations and laboratory analysis. The wavelength range of an echelle spectrograph is ultimately limited by the capabilities of the detector used to acquire the spectral data. Silicon based CCD, EMCCD and CMOS sensors typically enable measurements from 200nm to 1100nm. Infrared Laboratories and Catalina Scientific Instruments (CSI) have collaborated to demonstrate an application that combines IR Lab’s TRIWAVE camera with CSI’s EMU120/65 echelle spectrograph. The TRIWAVE camera covers a spectral range of 300nm to 1600nm, greatly increasing the wavelength range for applications using the EMU-120/65 spectrograph. With this increased capability, an opportunity exists for measuring the dielectric coating thickness of thin film by extracting and analyzing interference fringes from the spectral data. Methods and results of this measurement will be presented.

We report lattice-mismatched, uncooled, 2.2 µm wavelength cutoff, InGaAs photodiodes and balanced photoreceivers with bandwidth up to 25 GHz. The responsivity at 2.05 µm is 1.2 A/W, and the 1 dB compression, optical current handling of these photodiodes is 10 mA at 7 V reverse bias. Such high current handling capacity allows these photodiodes to operate with a higher DC local oscillator (LO) power, thus, allowing more coherent gain and shot noise limited operation. The impulse response of these devices show rise time / fall time of ~15 ps, and full width half maximum of ~20 ps.

Emerging short wavelength infrared (SWIR) LIght Detection And Ranging (LIDAR) and long range laser rangefinder systems, require large optical aperture avalanche photodiodes (APDs) receivers with high sensitivity and high bandwidth. A large optical aperture is critical to increase the optical coupling efficiency and extend the LIDAR sensing range of the above systems. Both APD excess noise and transimpedance amplifier (TIA) noise need to be reduced in order to achieve high receiver sensitivity. The dark current and capacitance of large area APDs increase with APD aperture and thus limit the sensitivity and bandwidth of receivers. Spectrolab has been developing low excess noise InAlAs/InGaAs APDs with impact ionization engineering (I²E) designs for many years and has demonstrated APDs with optical gain over 100 utilizing multiple period I²E structures in the APD multiplier. These high gain I²E APDs have an excess noise factor less than 0.15. With an optical aperture of 200 μm, low excess noise multiple periods I²E APDs have capacitances about 1.7 pF. In addition, optical gains of InAlAs based APDs show very little temperature dependence and will enable APD photoreceivers without thermal electric cooling.

Advanced electro-optical systems are designed towards a more compact, low power, and low cost solution with respect to traditional systems. Integration of several components or functionalities, such as infrared imager, laser designator, laser range finder (LRF), into one multi-function detector serves this trend. SNIR Read-Out Integrated Circuit (ROIC) incorporates this high level of signal processing and with relatively low power consumption. In this paper we present measurement results from a Focal Plane Array (FPA) where the SNIR ROIC is Flip-Chip bonded to a 15µm pitch VGA InGaAs detector array. The FPA is integrated into a metallic vacuum sealed package. We present InGaAs arrays with dark current density below 1.5 nA/cm² at 280K (typically 1fA), Quantum Efficiency higher than 80% at 1550 nm and operability better than 99.5%. The metallic package is integrated with a low power proximity electronics which delivers Camera Link output. The overall power dissipation is less than 1W, not including Thermal-Electric Cooling (TEC), which is required in some applications. The various active and passive operation modes of this detector will be reviewed. Specifically, we concentrate on the "high gain" mode with low readout noise for Low Light Level imaging application. Another promising feature is the Asynchronous Laser Pulse Detection (ALPD) with remarkably low detection thresholds.

Positive identification of personnel from a safe distance is a long-standing need for security and defense applications. Advances in computer face recognition have made this a reliable means of identification when facial imagery of sufficient resolution is available to be matched against a database of mug shots. Long-range identification at night requires that the face be actively illuminated; however, for visible and NIR illumination, the intensity required to produce high-resolution long-range imagery typically creates an eye-safety hazard. SWIR illumination makes active- SWIR imaging a promising approach to long-range night-time identification. We will describe an active-SWIR imaging system that is being developed to covertly detect, track, zoom in on, and positively identify a human target, night or day, at hundreds of meters range. The SWIR illuminator pans, tilts, and zooms with the imager to always just fill the imager field of view. The illuminator meets Class 1 eye-safety limits (safe even with magnifying optics) at the intended target, and meets Class 1M eye-safety limits (safe to the naked eye) at point-blank range. Close-up night-time facial imagery will be presented along with experimental face recognition performance results for matching SWIR imagery to a database of visible mug shots at distance.

For the past 15 years, Elbit Systems is developing time-resolved active laser-gated imaging (LGI) systems for various applications. Traditional LGI systems are based on high sensitive gated sensors, synchronized to pulsed laser sources. Elbit propriety multi-pulse per frame method, which is being implemented in LGI systems, improves significantly the imaging quality. A significant characteristic of the LGI is its ability to penetrate a disturbing media, such as rain, haze and some fog types. Current LGI systems are based on image intensifier (II) sensors, limiting the system in spectral response, image quality, reliability and cost. A novel propriety optical gating module was developed in Elbit, untying the dependency of LGI system on II. The optical gating module is not bounded to the radiance wavelength and positioned between the system optics and the sensor. This optical gating method supports the use of conventional solid state sensors. By selecting the appropriate solid state sensor, the new LGI systems can operate at any desired wavelength. In this paper we present the new gating method characteristics, performance and its advantages over the II gating method. The use of the gated imaging systems is described in a variety of applications, including results from latest field experiments.

Based on its well established 640×512 pixel, 15 µm pitch detector for a staring application, which is produced at AIM in high quantities at reproducible high yield and with superior performance, AIM has developed an MWIR and LWIR 1280×1024 pixel design with a 15 µm pixel pitch to make use of the advantages of large format detectors for IR systems applications. Benefitting from the continuous advancement of traditional liquid phase epitaxy (LPE) n-on-p technology, excellent electro-optical performance over a wide range of operating temperatures as well as enhanced long-term and thermal cycle stability have been achieved for this new and challenging detector format. In parallel, the performance of MCT material grown by molecular beam epitaxy (MBE), which is currently under development to take advantage of 3rd generation device architecture and the alternative GaAs substrate material, is evaluated for this application. In this paper, we will present the results of electro-optical detector characterizations and IR images of MWIR and LWIR 1280×1024 FPAs fabricated by LPE. We demonstrate the progress in MBE development at AIM and present electro-optical figures of merit, e.g., NETD and the operability of MWIR and LWIR 1280×1024 FPAs with MCT layers grown on GaAs by MBE.

Selex ES present progress on their FALCON HD1920x1080p 12μm pitch MWIR array. FALCON is buttable on 3- sides, enabling close packed mosaic arrays to be implemented. An update on FALCON array test results, progress on megapixel mosaic array development and HOT MCT is given.

Reducing an array’s pixel pitch reduces the size and weight of the focal plane array (FPA) and its associated dewar, cooler and optics. Higher operating temperatures reduce cool-down time and cooler power, enabling reduced cooler size and weight. High operating temperature small pitch (≤15 um) infrared detectors are therefore highly desirable. We have characterized a large number of MWIR and LWIR FPAs as a function of temperature and cutoff wavelength to determine the impact of these parameters on the FPA’s dark current, 1/f noise and defects. The 77K cutoff wavelength range for the MWIR arrays was 5.0-5.6 um, and 8.5-11 um for the LWIR arrays. DRS’ HDVIP^® FPAs are based on a front-side illuminated, via interconnected, cylindrical geometry, N+/N/P architecture. An FPA’s 1/f noise is manifested as a tail in the FPA’s rmsnoise distribution. We have found that the model-independent nonparametric skew [(mean–median)/standard deviation] of the rmsnoise distribution is a highly effective tool for quantifying the magnitude of an FPA’s 1/f noise tail. In this paper we show that a standard FPA’s 1/f noise varies as n_i (the intrinsic carrier concentration), in agreement with models that treat dislocations as donor pipes located within the P-volume of the unit cell. Nonstandard FPAs have been observed with systemic 1/f noise which varies as n_i².

In this paper, we report on results obtained both at CEA/LETI and SOFRADIR on p-on-n HgCdTe (MCT) grown by liquid phase epitaxy (LPE) Infra-Red Focal Plane Arrays (IR FPAs) for the Long-wave (LW) and the Very-long-wave (VLW) spectral ranges. For many years, p-on-n arsenic-ion implanted planar technology has been developed and improved within the framework of the joint laboratory DEFIR. Compared to n-on-p, p-on-n technology presents lower dark current and series resistance. Consequently, p-on-n photodiodes are well-adapted for very large FPAs operating either at high temperature or very low flux. The long wave (LW) spectral ranges have been firstly addressed with TV/4, 30 µm pitch FPAs. Our results showed state-of-the-art detector performances, consistent with "Rule 07" law [1], a relevant indicator of the maturity of photodiode technology. The low dark current allows increasing the operating temperature without any degradation of the performances. The subsequent development of p-on-n imagers has produced more compact, less energy consuming systems, with a substantial resolution enhancement. Space applications are another exciting but challenging domains and are good candidates for the p-on-n technology. For this purpose, TV/4 arrays, 30 µm pixel pitch, have been manufactured for the very long wave spectral range. For this detection range, the quality of material and reliability of technology are the most critical. Detectors with different cutoff wavelength have been manufactured to aim 12.5 µm at 78K, 12.5 µm at 40K and 15 µm at 78K. Electro-optical characterizations reveal homogeneous imagers with excellent current operabilities (over 99.9% at best). The results highlight the very good quality of p-on-n technology with carrier diffusion limited dark current, fitting the "Rule 07" law, and high quantum efficiency. Further process developments have been made to improve photodiodes performances. Especially the transition temperature where the dark current shifts from diffusion limited regime to another one, has been lowered by more than 10K. Extremely low dark current has been obtained, down to 50 e^-/s/pixel.

We have investigated the quantum effiency in HgCdTe photovoltaic pixel arrays employing a photon-trapping structure realized with a periodic array of pillars intended to provide broadband operation. We have found that the quantum efficiency depends heavily on the passivation of the pillar surface. Pillars passivated with anodicoxide have a large fixed positive charge on the pillar surface. We use our three-dimensional numerical simulation model to study the effect of surface charge and surface recombination velocity on the exterior of the pillars. We then evaluate the quantum efficiency of this structure subject to different surface conditions. We have found that by themselves, the surface charge and surface recombination are detrimental to the quantum efficiency but the quantum efficiency is recovered when both phenomena are present. We will discuss the effects of these phenomena and the trade offs that exist between the two.

We present a compact real-time multispectral camera operating in the mid-infrared wavelength range. Multispectral images of a scene with two differently spectrally signed objects and of a burning solid propellant will be shown. Ability of real-time acquisition will thus be demonstrated and spectra of objects will be retrieved thanks to inversion algorithm applied on multispectral images.

Numerical simulations play an important role in the development of large-format infrared detector array tech- nologies, especially when considering devices whose sizes are comparable to the wavelength of the radiation they are detecting. Computational models can be used to predict the optical and electrical response of such devices and evaluate designs prior to fabrication. We have developed a simulation framework which solves Maxwell’s equations to determine the electromagnetic properties of a detector and subsequently uses a drift-diffusion ap- proach to asses the electrical response. We apply these techniques to gauge the effects of cathode placement on the inter- and intra-pixel attributes of compositionally graded and constant Hg_1−xCd_xTe mid-wavelength infrared detectors. In particular, the quantum efficiency, nearest-neighbor crosstalk, and modulation transfer function are evaluated for several device architectures.

The video output of thermal imagers stayed constant over almost two decades. When the famous Common Modules were employed a thermal image at first was presented to the observer in the eye piece only. In the early 1990s TV cameras were attached and the standard output was CCIR. In the civil camera market output standards changed to digital formats a decade ago with digital video streaming being nowadays state-of-the-art.

The reasons why the output technique in the thermal world stayed unchanged over such a long time are: the very conservative view of the military community, long planning and turn-around times of programs and a slower growth of pixel number of TIs in comparison to consumer cameras. With megapixel detectors the CCIR output format is not sufficient any longer. The paper discusses the state-of-the-art compression and streaming solutions for TIs.

In uncooled LWIR microbolometer imaging systems, temperature fluctuations of FPA (Focal Plane Array) as well as lens and mechanical components placed along the optical path result in thermal drift and spatial non-uniformity. These non-idealities generate undesirable FPN (Fixed-Pattern-Noise) that is difficult to remove using traditional, individual shutterless and TEC-less (Thermo-Electric Cooling) techniques. In this paper we introduce a novel single-image based processing approach that marries the benefits of both statistical scene-based and calibration-based NUC algorithms, without relying neither on extra temperature reference nor accurate motion estimation, to compensate the resulting temperature-dependent non-uniformities. Our method includes two subsequent image processing steps. Firstly, an empirical behavioral model is derived by calibrations to characterize the spatio-temporal response of the microbolometric FPA to environmental and scene temperature fluctuations. Secondly, we experimentally establish that the FPN component caused by the optics creates a spatio-temporally continuous, low frequency, low-magnitude variation of the image intensity. We propose to make use of this property and learn a prior on the spatial distribution of natural image gradients to infer the correction function for the entire image. The performance and robustness of the proposed temperature-adaptive NUC method are demonstrated by showing results obtained from a 640×512 pixels uncooled LWIR microbolometer imaging system operating over a broad range of temperature and with rapid environmental temperature changes (i.e. from –5°C to 65°C within 10 minutes).

Infrared Focal Plane Arrays have been developed with reductions in pixel size below the Nyquist limit imposed by the optical systems Point Spread Function (PSF). These smaller sub diffraction limited pixels allows spatial oversampling of the image. We show that oversampling the PSF allows improved fidelity in imaging, resulting in sensitivity improvements due to pixel correlation, reduced false alarm rates, improved detection ranges, and an improved ability to track closely spaced objects.

This paper reports the development of a new microbolometer readout integrated circuit (MT3250BA) designed for high-resistance detector arrays. MT3250BA is the first microbolometer readout integrated circuit (ROIC) product from Mikro-Tasarim Ltd., which is a fabless IC design house specialized in the development of monolithic CMOS imaging sensors and ROICs for hybrid photonic imaging sensors and microbolometers. MT3250BA has a format of 320 × 256 and a pixel pitch of 50 µm, developed with a system-on-chip architecture in mind, where all the timing and biasing for this ROIC are generated on-chip without requiring any external inputs. MT3250BA is a highly configurable ROIC, where many of its features can be programmed through a 3-wire serial interface allowing on-the-fly configuration of many ROIC features. MT3250BA has 2 analog video outputs and 1 analog reference output for pseudo-differential operation, and the ROIC can be programmed to operate in the 1 or 2-output modes. A unique feature of MT3250BA is that it performs snapshot readout operation; therefore, the image quality will only be limited by the thermal time constant of the detector pixels, but not by the scanning speed of the ROIC, as commonly found in the conventional microbolometer ROICs performing line-by-line (rolling-line) readout operation. The signal integration is performed at the pixel level in parallel for the whole array, and signal integration time can be programmed from 0.1 µs up to 100 ms in steps of 0.1 µs. The ROIC is designed to work with high-resistance detector arrays with pixel resistance values higher than 250 kΩ. The detector bias voltage can be programmed on-chip over a 2 V range with a resolution of 1 mV. The ROIC has a measured input referred noise of 260 µV rms at 300 K. The ROIC can be used to build a microbolometer infrared sensor with an NETD value below 100 mK using a microbolometer detector array fabrication technology with a high detector resistance value (≥ 250 KΩ), a high TCR value (≥ 2.5 % / K), and a sufficiently low pixel thermal conductance (G_th ≤ 20 nW / K). The ROIC uses a single 3.3 V supply voltage and dissipates less than 75 mW in the 1-output mode at 60 fps. MT3250BA is fabricated using a mixed-signal CMOS process on 200 mm CMOS wafers, and tested wafers are available with test data and wafer map. A USB based compact test electronics and software are available for quick evaluation of this new microbolometer ROIC.

This paper reports the development of a new low-noise CTIA ROIC (MT6415CA) suitable for SWIR InGaAs detector arrays for low-light imaging applications. MT6415CA is the second product in the MT6400 series ROICs from Mikro-Tasarim Ltd., which is a fabless IC design house specialized in the development of monolithic imaging sensors and ROICs for hybrid imaging sensors. MT6415CA is a low-noise snapshot CTIA ROIC, has a format of 640 × 512 and pixel pitch of 15 µm, and has been developed with the system-on-chip architecture in mind, where all the timing and biasing for this ROIC are generated on-chip without requiring any external inputs. MT6415CA is a highly configurable ROIC, where many of its features can be programmed through a 3-wire serial interface allowing on-the-fly configuration of many ROIC features. It performs snapshot operation both using Integrate-Then-Read (ITR) and Integrate-While-Read (IWR) modes. The CTIA type pixel input circuitry has three gain modes with programmable full-well-capacity (FWC) values of 10.000 e-, 20.000 e-, and 350.000 e- in the very high gain (VHG), high-gain (HG), and low-gain (LG) modes, respectively. MT6415CA has an input referred noise level of less than 5 e- in the very high gain (VHG) mode, suitable for very low-noise SWIR imaging applications. MT6415CA has 8 analog video outputs that can be programmed in 8, 4, or 2-output modes with a selectable analog reference for pseudo-differential operation. The ROIC runs at 10 MHz and supports frame rate values up to 200 fps in the 8-output mode. The integration time can be programmed up to 1s in steps of 0.1 µs. The ROIC uses 3.3 V and 1.8V supply voltages and dissipates less than 150 mW in the 4-output mode. MT6415CA is fabricated using a modern mixed-signal CMOS process on 200 mm CMOS wafers, and tested parts are available at wafer or die levels with test reports and wafer maps. A compact USB 3.0 camera and imaging software have been developed to demonstrate the imaging performance of SWIR sensors built with MT6415CA ROIC

This paper presents a method which combines with Bilateral Filter and cross cumulative residual entropy. It will be applied to infrared and visible registration. In this algorithm, firstly, according to infrared image and optical image characteristics, we put forward edge extraction algorithm based on the Bilateral Filter. Secondly, we use Cross Cumulative Residual Entropy (CCRE) as the similarity measure to match the reference images and transformed images effectively. Finally, we introduce the idea of calibration to reduce operation time. Bilateral filter can reduce noise and protect edge, and cross cumulative residual entropy uses cumulative distribution function instead of probability density function to overcome the noise on the local minima. The experiment proved that registration is effective.

This paper presents a digital ROIC for staring type arrays with extending counting method to realize very low quantization noise while achieving a very high charge handling capacity. Current state of the art has shown that digital readouts with pulse frequency method can achieve charge handling capacities higher than 3Ge^- with quantization noise higher than 1000e^-. Even if the integration capacitance is reduced, it cannot be lower than 1-3 fF due to the parasitic capacitance of the comparator. For achieving a very low quantization noise of 200 electrons in a power efficient way, a new method based on measuring the time to measure the remaining charge on the integration capacitor is proposed. With this approach SNR of low flux pixels are significantly increased while large flux pixels can store electrons as high as 2.33Ge^-. A prototype array of 32x32 pixels with 30μm pitch is implemented in 90nm CMOS process technology for verification. Simulation results are given for complete readout.

Design of a 90×8 CMOS readout integrated circuit (ROIC) based on pixel level digital time delay integration (TDI) for scanning type LWIR focal plane arrays (FPAs) is presented. TDI is implemented on 8 pixels which improves the SNR of the system with a factor of √8. Oversampling rate of 3 improves the spatial resolution of the system. TDI operation is realized with a novel under-pixel analog-to-digital converter, which improves the noise performance of ROIC with a lower quantization noise. Since analog signal is converted to digital domain in-pixel, non-uniformities and inaccuracies due to analog signal routing over large chip area is eliminated. Contributions of each pixel for proper TDI operation are added in summation counters, no op-amps are used for summation, hence power consumption of ROIC is lower than its analog counterparts. Due to lack of multiple capacitors or summation amplifiers, ROIC occupies smaller chip area compared to its analog counterparts. ROIC is also superior to its digital counterparts due to novel digital TDI implementation in terms of power consumption, noise and chip area. ROIC supports bi-directional scan, multiple gain settings, bypass operation, automatic gain adjustment, pixel select/deselect, and is programmable through serial or parallel interface. Input referred noise of ROIC is less than 750 rms electrons, while power consumption is less than 20mW. ROIC is designed to perform both in room and cryogenic temperatures.

Quantum structures base on type-II In(Ga)Sb quantum dots (QDs) embedded in an InAs matrix were used as active material for achieving long-wavelength infrared (LWIR) photodetectors in this work. Both InAs and In(Ga)Sb are narrow band semiconductor materials and known to possess a large number of surface states, which apparently play significant impact for the detector’s electrical and optical performance. These surface states are caused not only by material or device processing induced defects but also by surface dangling bonds, oxides, roughness and contaminants. To experimentally analyze the surface states of the QD structures treated by different device fabrication steps, atomic force microscopy (AFM), scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and X-ray photoelectron spectroscopy (XPS) measurements were performed. The results were used to optimize the fabrication process of the LWIR photodetectors in our ongoing project. The dark current and its temperature dependence of the fabricated IR photodetectors were characterized in temperature range 10 K to 300 K, and the experiment results were analyzed by a theoretic modeling obtained using simulation tool MEDICI.

We report on the device characterization of In(Ga)Sb/InAs quantum dots (QDs) based photodetectors for long wave IR detectors. The detection principle of these quantum-dot infrared photodetectors (QDIPs) is based on the spatially indirect transition between the In(Ga)Sb QDs and the InAs matrix, as a result of the type-II band alignment. Such photodetectors are expected to have lower dark currents and higher operating temperatures compared to the current state of the art InSb and mercury cadmium telluride (MCT) technology. The In(Ga)Sb QD structures were grown using metal-organic vapour-phase epitaxy and explored using structural, electrical and optical characterization techniques. Material development resulted in obtaining photoluminescence up to 10 μm, which is the longest wavelength reported in this material system. We have fabricated different photovoltaic IR detectors from the developed material that show absorption up to 8 μm. Photoresponse spectra, showing In(Ga)Sb QD related absorption edge, were obtained up to 200 K. Detectors with different In(Ga)Sb QDs showing different cut-off wavelengths were investigated for photoresponse. Photoresponse in these detectors is thermally activated with different activation energies for devices with different cut-off wavelengths. Devices with longer cut-off wavelength exhibit higher activation energies. We can interpret this using the energy band diagram of the dots/matrix system for different QD sizes.

Considering the importance of In(Ga)As/GaAs QDIPs, a post-growth method had been developed for enhancing QDIP characteristics using low energy light ion (H-) implantation. Dark current density was reduced by about five orders for the implanted devices due to the reduction in field assisted tunneling process for dark current generation, even at a very high bias of operation. Stronger multicolor mid wavelength photo response (~5.6 µm) was achieved at a very low bias of operation for the implanted device.

While InGaAs-based focal plane arrays (FPAs) provide excellent detectivity and low noise for SWIR imaging applications, wider scale adoption of systems capable of working in this spectral range is limited by high costs, limited spectral response, and costly integration with Si ROIC devices. RTI has demonstrated a novel photodiode technology based on IR-absorbing solution-processed PbS colloidal quantum dots (CQD) that can overcome these limitations of InGaAs FPAs. The most significant advantage of the CQD technology is ease of fabrication. The devices can be fabricated directly onto the ROIC substrate at low temperatures compatible with CMOS, and arrays can be fabricated at wafer scale. Further, device performance is not expected to degrade significantly with reduced pixel size. We present results for upward-looking detectors fabricated on Si substrates with sensitivity from the UV to ~1.7 µm. We further show devices fabricated with larger size CQDs that exhibit spectral sensitivity that extends from UV to 2 µm.

Current infrared imaging systems monitor emission from a given scene over a broad spectral range, which results with "black and white" images. As a result, there is ever increasing emphasis on the development of new, on the pixel level, infrared imaging technology that can provide spectral information. Attempts at creating a robust imaging system with spectral information have been made through a network of external optics, which results with a high cost and large system package. Here, we propose a metamaterial design that resonantly couples to an infrared photodetector for enhanced performance.

SCD has developed a new 1920x1536 / 10 μm digital Infrared detector for the MWIR window named Blackbird. The Blackbird detector features a Focal Plane Array (FPA) that incorporates two technological building blocks developed over the past few years. The first one is a 10 μm InSb pixel based on the matured planar technology. The second building block is an innovative 10 μm ReadOut Integrated Circuit (ROIC) pixel. The InSb and the ROIC arrays are connected using Flip-Chip technology by means of indium bumps. The digital ROIC consists a matrix of 1920x1536 pixels and has an analog to digital (A/D) converter per-channel (total of 1920x2 A/Ds). It allows for full frame readout at a high frame rate of up to 120 Hz. Such an on-chip A/D conversion eliminates the need for several A/D converters with fairly high power consumption at the system level. The ROIC power consumption at maximum bandwidth is less than 400 mW. It features a wide range of pixel-level functionality such as several conversion gain options and a 2x2 pixel binning. The ROIC design makes use of the advanced and matured CMOS technology, 0.18 μm, which allows for high functionality and relatively low power consumption. The FPA is mounted on a Cold-Finger by a specially designed ceramic substrate. The whole assembly is housed in a stiffened Dewar that withstands harsh environmental conditions while minimizing the environment heat load contribution to the heat load of the detector. The design enables a 3-megapixel detector with overall low size, weight, and power (SWaP) with respect to comparable large format detectors. In this work we present in detail the characteristic performance of the new Blackbird detector.

Low cost IR Sensors are needed for a variety of Defense and Commercial Applications as low cost imagers for various Army and Marine missions. SiGe based IR Focal Planes offers a low cost alternative for developing wafer-level shortwave infrared micro-camera that will not require any cooling and can operate in the Visible-NIR band. The attractive features of SiGe based IRFPA’s will take advantage of Silicon based technology, that promises small feature size and compatibility with the low power silicon CMOS circuits for signal processing. SiGe technology offers a low cost alternative for developing Visible-NIR sensors that will not require any cooling and can operate from 0.4- 1.7 microns. The attractive features of SiGe based IRFPA’s will take advantage of Silicon based technology that can be processed on 12-inch silicon substrates, that can promise small feature size and compatibility with the Silicon CMOS circuit for signal processing. In this paper, we will discuss the design and development of Wafer-Level Short Wave Infrared (SWIR) Micro-Camera. We will discuss manufacturing approaches and sensor configurations for short wave infrared (SWIR) focal plane arrays (FPAs) that significantly reduce the cost of SWIR FPA packaging, optics and integration into micro-systems.

We show simulation results of the integration of a nanoantenna in close proximity to the active material of a photodetector. The nanoantenna allows a much thinner active layer to be used for the same amount of incident light absorption. This is accomplished through the nanoantenna coupling incoming radiation to surface plasmon modes bound to the metal surface. These modes are tightly bound and only require a thin layer of active material to allow complete absorption. Moreover, the nanoantenna impedance matches the incoming radiation to the surface waves without the need for an antireflection coating. While the nanoantenna concept may be applied to any active photodetector material, we chose to integrate the nanoantenna with an InAsSb photodiode. The addition of the nanoantenna to the photodiode requires changes to the geometry of the stack beyond the simple addition of the nanoantenna and thinning the active layer. We will show simulations of the electric fields in the nanoantenna and the active region and optimized designs to maximize absorption in the active layer as opposed to absorption in the metal of the nanoantenna. We will review the fabrication processes.

We present performance calculations for a MEMS cantilever device for sensing heat input from convection or radiation. The cantilever deflects upwards under an electrostatic repulsive force from an applied periodic saw-tooth bias voltage, and returns to a null position as the bias decreases. Heat absorbed during the cycle causes the cantilever to deflect downwards, thus decreasing the time to return to the null position. In these calculations, the total deflection with respect to absorbed heat is determined and is described as a function of time. We present estimates of responsivity and noise.

Vanadium oxide (VO_x) thin films have been intensively studied as an imaging material for uncooled microbolometers due to their low resistivity, high temperature coefficient of resistivity (TCR), and low 1/f noise. Our group has studied pulsed DC reactive sputtered VO_x thin films while reactive ion beam sputtering has been exclusively used to fabricate the VO_x thin films for commercial thermal imaging cameras. The typical resistivity of imaging-grade VO_x thin films is in the range of 0.1 to 10 ohm-cm with a TCR from -2%/K to -3%/K. In this work, we report for the first time the use of a new biased target ion beam deposition tool to prepare vanadium oxide thin films. In this BTIBD system, ions with energy lower than 25ev are generated remotely and vanadium targets are negatively biased independently for sputtering. High TCR (<-4.5%/K) VO_x thin films have been reproducibly prepared in the resistivity range of 10³-10⁴ ohm-cm by controlling the oxygen partial pressure using real-time control with a residual gas analyzer. These high resistivity films may be useful in next generation uncooled focal plane arrays for through film rather than lateral thermal resistors. This will improve the sensitivity through the higher TCR without increasing noise accompanied by higher resistance. We report on the processing parameters necessary to produce these films as well as details on how this novel deposition tool operates. We also report on controlled addition of alloy materials and their effects on VO_x thin films’ electrical properties.

In this paper we present a room-temperature micro-photonic bolometer that is based on the whispering gallery mode of dielectric resonator (WGM). The sensing element is a hollow micro-spherical optical polymeric resonator. The hollow resonator is filled with a fluid (gas or liquid) that has a large thermal expansion. When an incoming radiation impinges on the resonator is absorbed by the absorbing fluid leading to a thermal expansion of the micro-resonator. The thermal expansion induces changes in the morphology of the resonator (size and index of refraction), that in turn lead to a shift of the optical resonances (WGM). The optical resonances are typically excited using a single mode optical fiber. The preliminary analysis presented in this paper, shows that these sensors can measure energies of the order of 0.1J/m².

For the development of small and low cost microbolometer, wafer level reliability characterization techniques of vacuum packaged wafer are introduced. Amorphous silicon based microbolometer-type vacuum sensors fabricated in 8 inch wafer are bonded with cap wafer by Au-Sn eutectic solder. Membrane deflection and integrated vacuum sensor techniques are independently used to characterize the hermeticity in a wafer-level. For the packaged wafer with membrane thickness below 100um, it is possible to determine the hermeticity as screening test by optical detection technique. Integrated vacuum sensor having the same structure as bolometer pixel shows the vacuum level below 100mTorr. All steps from packaging process to fine hermeticity test are implemented in wafer level to prove the high volume and low cost production.

Mosaic pixel FPA technology comprises a novel microbolometer array design which, together with advanced packaging and integrated optics, can provide enhanced performance in short range sensing applications. Initially developed for passive infrared (PIR) security sensors, the technology can be applied to other non-military applications where a large pixel size is acceptable and a high detective performance is required. In this paper we discuss to two applications in depth: low cost thermography and non-imaging cheap sensors for pedestrian detection and other applications. Both have the advantage of very low NETD. We also discuss development of miniaturised IR sensors, as initially conceived for mosaic pixel technology.