This PDF file contains the front matter associated with SPIE Proceedings Volume 12107 including the Title Page, Copyright information, Table of Contents, and Committee pages.

The challenges of size, weight, power consumption, and the cost of federated sensor systems for defense applications can be mitigated by exploring solutions derived from collaborative activities across government, industry, and academia. But sensor integration is illusive. For example, new vehicles are almost always developed by a single prime contractor; sensors are often identified as Contractor Furnished Material or Government Furnished Equipment and acquired by the “Prime.” This approach leads to federate architectures; sensor upgrades or new additions often show the “Christmas tree” effect, where sensors are more or less “hung” on the platform. This talk will explore novel approaches to integrating sensors needed to provide enhanced or new capabilities. Integrated sensors can support multiple missions performed by a single platform alone or with other manned or unmanned platforms, using common standards emerging from the DoD and Industry.

In this work, the characteristics of metamorphic grown InGaAs based and InAs/GaSb/AlSb/GaSb Type-II superlattice based extended short wave infrared(eSWIR) detectors are reported. The InGaAs detector was a p-i-n photodiode(PD) with a planar structure, and the T2SL detector was an nBn barrier infrared diode with mesa structure. In case of InGaAs detector, the cutoff wavelength is 2.35 μm and average quantum efficiency(QE) in the 1.1-2.2μm spectral range is 70.1% under front-side illumination condition and 200 K operation. At 200K, the dark current density is 6.80×10^-9 A/cm² under -0.1 V bias and the expected peak specific detectivity is 2.33×10¹³ cm∙㎐ ^1/2/W. In case of T2SL, the cutoff wavelength is 2.45 μm and average QE in the 1.1-2.2 μm spectral range is 51.3 % at 200 K. The dark current density at 200 K is 1.1×10^-7 A/cm² and the expected peak specific detectivity is 4.68×10¹²cm∙㎐ ^1/2/W at 200 K. The 1280×1024 infrared focal plane array (FPA) with the pixel size of 10 μm is fabricated and hybridized with readout integrated circuit. The InGaAs FPA show relatively low operability due to defect or cross hatch pattern of wafer while its specific detectivity is higher than T2SL.

Event-based imagers are an emerging class of sensors with demonstrated advantages relative to traditional imagers. Eventbased vision sensors have a limited number of output bits that are only responsive to image variations, thus overcoming the speed and power constraints of the conventional imagers based on image integration. So far, event-based vision has been implemented in visible CMOS sensors. SCD has developed a new event-based VGA/10µm InGaAs sensor that is sensitive in the Visible to SWIR band (600–1700nm) thus extending the standard imaging capabilities such as day light, low-light level, see-through fog and dust. Another novelty of this sensor is that the event channel outputs in parallel to a conventional integrating fast imaging channel. Moreover, the event channel can be reconfigured to provide a fast laser pulse detection mode, which also outputs in parallel to the integrated image. The new ROIC outputs standard video at 13 bit resolution with a high frame rate of 800 frames per second and can double this rate by lowering the resolution to 11 bit. The Event channel can reach up to 25 kHz of negative, null, or positive signal and the laser channel can double this output providing a single bit detection frame up to 50 kHz. In this work, we will elaborate on the architecture, key features, and preliminary simulations of the ROIC and sensor

Shortwave IR (SWIR) sensors made using colloidal quantum dot photodiodes offer CMOS-like opportunities for highly scalable, small pixel pitch sensors, owing to their straightforward, monolithic integration with silicon circuitry. SWIR Vision Systems began to realize this potential when it introduced its 2.1 MP Acuros cameras to the industrial, scientific, and commercial imaging markets in 2018. Other opportunities for this detector technology can be found in the need for new sensor technologies in the development of cost and resolution scalable direct time of flight depth sensing systems for consumer and automotive applications. But to realize this potential, this relatively new detector system must also be shown to meet thermal and environmental conditions found in consumer and automotive devices. This paper will provide an overview of the performance of our high definition sensors; and show <3 ns rise/fall time results from testing the response time of the photodiode structure using a pulsed laser sources. It will also present data demonstrating stable device operation at elevated temperature and humidity conditions.

For several years now, LYNRED, CEA-LETI and CEA-IRFU have been involved in the development of large area, very high performance NIR retinas for astronomy, in the context of the ALFA program (Astronomical Large Format Array). It aims at demonstrating the ability to produce in Europe low flux 2kx2k arrays exhibiting the very high performances required by science applications. In this context, high performance means very low dark current (below 0.1 e/s/px) with high QE (above 80%). LETI and LYNRED succeeded this year in the fabrication of a 2kx2k array, with very high uniformity as characterized at IRFU. One of those arrays will be used on the CAGIRE camera of the SVOM mission, aiming at observing afterglows of gamma ray bursts. Additional studies are ongoing on test arrays manufactured with the same technology to assess the behavior of this technology in terms of persistence and radiation hardness for space use.

The short wave infrared (SWIR) spectral band is an emerging domain thanks to its large potential. Close to VISible/Near Infrared wavelengths, SWIR images interpretation is made easier for the users. In this spectral region, new opportunities can be found in several fields of applications such as defense and security (night vision, active imaging), space (earth observation), transport (automotive safety), or industry (nondestructive process control, food and plastic sorting). In the frame of this paper, two different developments of the InGaAs technology addressing emerging fields of SWIR imaging are described: pixel pitch reduction and multi-spectral imaging. In pixel pitch reduction the obvious objective is to increase the imaging resolution without jeopardizing system cost. Multi-spectral resolution deals, on the other hand, with interposition of pixelated filters in the optical path right onto SWIR focal plane arrays (FPA) to enable a real time spectral analysis of recorded SWIR images.

Recent advances in short-wave infrared (SWIR) technology including numerous new applications in civil areas, fusion with visible wavelengths, and integration with active imaging systems triggered the SWIR photodetector research at ASELSAN for both passive and active imaging. SWIR focal plane arrays with a 640x512 format and 15μm pitch were developed and coupled with ASEL64015C readout circuits which had been designed at ASELSAN as well. Through extensive research and development dark current density values <10 nA/cm² (at 20°C) and operabilities >;99% were achieved. This paper reviews the work that has been conducted on SWIR detector development at ASELSAN.

Increasing shortwave infrared (SWIR) sensor performance requirements have pushed traditional HOT detector technologies to their limits. Collins Aerospace Princeton, a Raytheon Technologies (RTX) Company, has answered this call by looking beyond dark current reduction, and leveraging its onshore foundry capabilities to develop unprecedented, high performance photodetector array (PDA) technologies to better serve both passive and active imaging applications. In this work, Collins Aerospace Princeton offers an update on several previously presented, PDA-specific development fronts as well as offering introductions into other novel efforts. In addition to presenting current state-ofthe-art (SOA) InGaAs dark current performance, results related to mesa-structure PDAs for modulation transfer function (MTF) improvement and hybridization capacitance reduction for active imaging noise equivalent irradiance (NEI) improvement are offered. Additionally, focal plane array (FPA) interconnection improvement techniques and results for yield improvement and cost reduction are presented. Finally, results related to the three most advanced and nascent development tracks, avalanche photodiode (APD), PDA metallization and single side bumped FPA, are introduced. Collins Aerospace Princeton’s APD technology is in direct response to the challenging size, weight, and power (SWaP) and NEI performance requirements of active imaging applications. Similarly, Collins Aerospace Princeton’s PDA metallization technology, inspired by silicon-based brethren, facilitates greater integration capability on the PDA itself, which subsequently allows for greater functionality and performance at every pixel location. The most recently developed single side bumped FPA will dramatically improve operability with reduced cost. Overall, these PDA-specific developments represent the most innovative SWIR technology portfolio known to date.

This paper reviews the camera development efforts at Sensors Unlimited Inc. (SUI), a Collins Aerospace company, focused on serving multi-mode short-wavelength infrared (SWIR) applications while maintaining a low size, weight, and power (SWaP) footprint. Increasingly over the last decade, end users have looked to SWIR to support not only low-noise passive imaging, but also active illumination applications. Hence, cameras that include provisions to specifically support both modalities, passive and active imaging, have been given the moniker, “Multi-Mode.” In this work, SUI offers an overview of the passive and active imaging performance of the multi-mode cameras in its technology portfolio juxtaposing the traits of each. Finally, an outlook for future work in the area of multi-mode SWIR camera development is presented.

State-of-art detectors having response over 2.0+ μm wavelengths require cryogenic coolers to improve SNR and achieve high sensitivity. Next generation detectors are required to operate at room temperature (300 K) to fit small form factor sensor modules for SWaP-efficient space instruments and defense applications. III-V materials-based p-i-n detectors (e.g. InGaAs) over 2.0+ μm wavelengths suffer from lattice mismatch with substrate, resulting in high dark currents, low sensitivity (low SNR), and needing cooling. An avalanche photodiode (APD) with high gain will significantly increase sensitivity above p-i-n detector solutions; however, dark current also multiplies under high gain, leading to increased noise. An APD’s material system dictates noise associated with gain process and depends on ratio of ionization coefficient (hereinafter mentioned as k or k-factor) which dictate the APD excess noise. In APDs, dark current and excess noise limit useful gain and hence the SNR of detection systems. Therefore, it is essential to reduce k-factor and dark current of an APD. We present a first in the world low-noise, high-gain, and high bandwidth 2.0+ μm uncooled APD having k factor of <0.01 enabling low excess noise at a given gain. The APD uses a novel structure and a bandstructure-engineered multiplication region based on III-V material system to reduce k-factor to near zero. We present the APD SACM device design, their simulations, and experimental results of fabricated APD devices. The uncooled 2.0+μm APD matches advantages offered by HgCdTe APDs having k~ zero, but with low dark currents at near room-temperature operation, and also mitigates both HgCdTe APDs and standard III-V p-i-n deficiencies to become an ideal solution benefiting to extend short-wave IR band to 2.0 +μm for imaging applications.

We report new results on Linear Mode HgCdTe electron Avalanche Photodiodes (e-APDs) for applications in the 500 - 3000 nm band at 200-240K with high gain, low excess noise factor, low dark current density and high quantum efficiency. Results from two classes of devices will be reported: first the conventional HgCdTe e-APD grown by LPE with homogeneous composition and second bandgap engineered HgCdTe e-APDs grown by MBE. Detailed characterization data of the e-APDs including gain, dark current density and excess noise factor will be reported and compared with modeling results.

We present the results from a radiation damage test of a HgCdTe avalanche photodiode (APD) array developed by Leonardo UK for potential NASA space lidar applications. The device being tested is a high-speed variant of the SAPHIRA family HgCdTe APD arrays used in astronomy. Test results show that the device remains fully operational at normal bias level under proton flux anticipated in space. The average dark current started to rise above the noise floor after 2 krad(Si) accumulated dose. However, the APD dark currents increased by more than an order of magnitude after the device was warmed up to room temperature for two hours and cooled to 80 K again. The dark currents returned to their pre-irradiation levels after being heated to 344 K (70°C) for about two hours. There was little change in the quantum efficiency and APD gain after 50 krad(Si) and annealing.

Avalanche photodiodes (APDs) are critical components for a variety of remote sensing applications, particularly for 3D imaging using light detection and ranging (LiDAR). APDs can provide higher sensitivity and faster response times than traditional PIN diodes due to their internal gain. To apply LiDAR to gas monitoring applications, including greenhouse gases, APDs need to be sensitive further into the infrared than Si APDs can detect. This work investigates an absorber that is sensitive to 2 μm and compatible with an APD. A separate absorption, charge, and multiplication (SACM) heterostructure is often used to reduce the dark current of an infrared APD. In a SACM design, the absorber is placed in a low field region to minimize tunneling and the multiplier is placed in a high field region to maximize impact ionization. We have previously explored high performance multipliers that are lattice matched to InP substrates. In this work, we explore a candidate lattice-matched absorber, an In_0.53Ga_0.47As/GaAs_0.51Sb_0.49 Type II superlattice (T2SL). We have demonstrated photoluminescence at 2 μm using a 5 nm InGaAs/5 nm GaAsSb T2SL structure. We have grown and fabricated 1-micron thick PIN diodes with this absorber material and obtained an n-type background carrier concentration of 5×10¹⁵ cm^-3 . We are currently undertaking the radiometric characterization of these devices to support their integration into a SACM APD.

In this work, we designed an InGaAs APD with a higher photocurrent to dark current ratio than a regular APD. The improvement is based on optical confinement in an optical resonator, which is able to increase the optical intensity in the detector volume and thus its quantum efficiency. With optical confinement, the absorbing layer can be 20 times thinner than the regular APD, reducing the dark current by the same amount and still be able to produce 90.9% of the photocurrent. The Ip/Id ratio can thus be increased by 18.2 times in concomitant with a lower operating voltage. Higher photocurrent can also be obtained using a thicker absorber. To further increase the detection sensitivity, we designed an efficient InGaAsP LED having the similar resonator geometry. The resonator geometry enables more collimated emission and increases the optical power theoretically by more than 36 times compared with a regular LED. Integrating the resonant APD and LED together will yield a powerful SWIR transceiver for various low light, LIDAR, and 3-dimensional imaging applications.

Background doping polarity type is a critical parameter for avalanche photodiode performance. We demonstrated a technique using capacitance-voltage (CV) measurements on double mesa structures with a p-i-n or n-i-p homojunctions to determine the polarity type of the unintentionally doped intrinsic (uid) region. CV measurements scale with the size of the mesa and enable design flexibility in producing variable top or bottom mesa diameters. We designed and tested AlGaAsSb and AlInAsSb structures and performed measurements at varying temperatures. Measurements varied with the top mesa, indicating the p-n junction is located between the p-region and the uid region, therefore it is n-type.

Recently a group from University of Virginia, demonstrated InAlAsSb digital alloy APDs operating in the 1-2 μm wavelengths with a very low excess noise, equivalent to silicon APDs. With a digital-alloy In0.3Al0.7AsSb multiplier, the excess noise is similar to that of Si APDs and the impact ionization parameter k is about 0.02 at gains >10. Using this digital alloy detector technology, our modeling calculations show that a noise equivalent power (NEP) comparable to HgCdTe APD receivers can be achieved at TE-cooled temperatures. Acqubit has designed and developed a 1 GHz receiver operating at -30°C using the InAlAsSb digital alloy APD designed for 2 μm wavelength operation. We measured an NEP of 600 fW/√Hz at 1.5 μm wavelength. In this presentation, we will present the receiver design and characterization results and modeling data to show the potential to achieve high sensitivity comparable to HgCdTe and Si receivers.

The recent advent of high operating temperature infrared detectors allowed operating them at temperatures in excess of 150K without compromising performance indices typical of their 77K predecessors. These substantially relaxed cooling constraints along with a fundamentally higher coefficient of thermodynamic performance called for the development of a next-generation of low size, weight, and power cryocoolers purposely tailored for such high operating temperature detectors. Unfortunately, the most up-to-date low size, weight, and power cryocoolers are no more than downscaled and slightly lower-priced replicas of their low temperature predecessors. They commonly rely on gaseous helium as the working agent, metal stacked-screens regenerative heat exchangers, “moving magnet” dual-piston compressors, pneumatic expanders driven by differential pistons, mechanical springs, etc. Because of the inherent limitations, the currently achieved reliability and cost indices still prevent the broad use of cooled infrared imaging in the price-conscious and highly competitive commercial segment of the infrared imaging marketplace. From the very moment of its inception in 2018, CryoTech focused on disruptive innovation, enabling drastic reduction of ownership costs by deploying alternative, cost-effective technological solutions. The list of novelties includes but is not limited to: alternative working agent, low-cost microfiber regenerative heat exchanger, “moving iron” single-piston compressor with optional tuned dynamic counterbalancer, rodless pneumatic displacer, magnet springs, etc. The authors present the outcomes of the full-scale feasibility study and prototype life testing.

Environment awareness and eco design principles are increasingly required during the development process of new products. Estimations of a products environmental impact will require a full life cycle analysis. Once the main environmental impacts have been identified, plans can be defined for potential reduction of these impacts. Alternative design concepts will need to be studied and decisions will need to take into account applicable legislation and potential environmental impact. For cryocoolers, besides considerations on used materials, supply chain and transportation aspects, the main influent topics that come to mind are related to the mass, size and power consumption of the final product. Here comes a paradox: further reduction of these characteristics on eco design approach is quite challenging as cryocoolers have been lately widely used in handheld sighting devices where size, mass and power have already been significantly pushed to the limit due to user requirements. Looking back in the recent and young history of cryocoolers, Stirling type mostly, the trend for mass, size and power reduction appears obvious when reviewing some landmark models from the last 40 years. Regarding the Thales range of rotary Stirling coolers, the evolution from the RM8 cooler developed in the eighties to the miniaturized RM2 from the nineties and to the recently released RMs1, is spectacular. These upgrades were possible due to improvements in detectors technologies (new detector materials, IDCA configuration, hot detectors, etc.) but also due to the continuous push to improve cryocooler performances. The combination of both cooler and detector developments enabled the SWaP progress seen in the past years. This paper will review the various environmental impact improvements made on these three generations of coolers: size and weight reduction, efficiency improvement, acoustic behavior, reliability, materials, etc. The analysis will reflect the cooler and its accessories, such as the electronic board.

In recent years, the trend of moving IR detectors to operate from standard 77K to the High Operating Temperature (HOT) of 150K, drives RICOR’s onward development focusing on SWaP-C, a new family of miniature cryocoolers, alongside continuing to make improvements to existing cryocooler models. The main objective for the development of a new family of cryocoolers is to focus on SWap-C by creating cryocoolers that maintain a small size, low weight, low power consumption and an attractive cost. This effort has yielded advanced Linear & Rotary miniature Cryocoolers named K580, K588 and K590. This paper will review the progress made with qualification and the move to production of the K590 Linear Dual Opposed model using customized cold finger & engineering efforts to optimize the K588 model that based on the same compact dual opposed compressor integrated with a common cold finger. In addition, the paper will present the improvements made for K580I Integral Rotary Model with lower induced force level and will review the accumulated experience of 3 mature models under production named K527, K562S and K562SI.

The development of mechanical cryocoolers over the past two decades has now reached a point where cryocooler life time no longer needs to limit system reliability or availability. However, to avoid peripheral failure mechanisms becoming dominant on the IDCA level, careful consideration needs to be given to integration aspects. In this presentation, ongoing activities at Thales Cryogenics to make previously field-proven high-availability technology suitable for infrared detection applications will be discussed. One technology presented will be a SADA-compatible flexure-bearing Stirling cooler with an upgraded bearing design based on a previous slip-on design for HTS telecommunications base stations [1]. Another design that will be discussed is a similarly-sized pulse-tube cooler and its usability for infrared sensor cooling. Both technologies will be compared and present and future work will be highlighted.

In а concept of Integrated Dewar-Detector-Cooler Assembly, the entire cold assembly (substrate, infrared focal plane array, cold shield and cold filter) is mounted upon the distal (cold) tip of the thin-walled metal cold finger having no mechanical contact with the warm shroud of the evacuated Dewar. This forms a slender, tip-mass cantilever, the dynamic properties of which depend, amongst other factors, on the nonlinear interaction (rattling) of the cold finger tube with displacer cartridge arranged slidably inside the cold finger bore. The resonant frequency of such a weakly nonlinear and lightly damped mechanical system usually falls within the range of operational vibration profiles. This results in extremely high susceptibility to vibrational extremes. Explicit knowledge of damping ratios and resonant frequencies is, therefore, critical for predicting dynamic responses under adverse environmental conditions. Unfortunately, because of the above-mentioned nonlinearities, analytical assessments are not feasible. Experimental evaluation involves making mockups instrumented with contactless sensors; the entire procedure is quite laborious, expensive, requires special equipment/skills, is not always accurate and is not applicable to evacuated and sealed operational IDDCA. The author suggests a non-invasive and express approach to evaluating the above mentioned modal properties. The procedure relies on measuring the local frequency response function (accelerance) of the cold finger base and applying a curve-fitting procedure for extracting the dynamic properties of Focal Plane Array (modal mass, frequency and damping). Theoretical predictions are supported by a full-scale experimentation.

This presentation discusses the current performance and maturing industrial base for III-V antimony (Sb)-based strained layer superlattice (SLS) infrared focal plane arrays (IRFPAs), and their progression following the Vital Infrared Sensor Technology Acceleration (VISTA) program. VISTA was a five-year DoD Tri-Service program that established an entirely new domestic industrial base revolving around advanced cooled infrared focal plane array (IRFPA) technology. The program’s objectives included IRFPA technology that had to be affordable, highly producible, and it had to offer performance advantages over current solutions. To this end, VISTA focused on III-V Sb-based strained layer superlattice (SLS) detector material systems. This presentation highlights these various performance and manufacturing improvements since the completion of VISTA and emphasizes collaborative approaches that could benefit large technology development efforts.

The InAs/InAsSb (Gallium-free) type-II strained-layer superlattice (T2SLS) has emerged in recent years as a viable infrared detector material. In particular, mid-wavelength InAs/InAsSb T2SLS focal plane array (FPA) based on the nBn detector architecture exhibits good operating characteristics at 160 K, demonstrating a considerably operating temperature advantage over InSb FPAs. In the long and very long cutoff wavelengths, InAs/InAsSb T2SLS detectors with n-type absorbers are limited in their attainable quantum efficiency (QE) due to short hole diffusion lengths and relatively modest absorption coefficients. We have explored long and very long wavelength InAs/InAsSb T2SLS complementary barrier infrared detectors (CBIRDs) that contain p-type absorber layers in order to take advantage of the longer electron diffusion length for QE enhancement. We also discuss recent development of the InAs/InAsSb T2SLS infrared detectors at the Jet Propulsion Laboratory for NASA Earth Science applications, including long-wavelength infrared FPAs for land imaging, and mid-wavelength infrared FPAs for CubeSat hyperspectral imaging.

The Vital Infrared Sensor Technology Acceleration (VISTA) program was a tri-service initiative designed to maintain US military superiority in infrared sensor capabilities. VISTA focused in part on III-V antimony-based infrared focal plane arrays and was highly successful in maturing and transitioning this technology into deployed systems. An integral part of the program was the VISTA Industrial Consortium (IC), in which government trusted entities (JPL and NRL) developed and transferred technology to participating US manufacturers which in turn sponsored the consortium’s efforts. The IC has continued in a follow-on phase after the initial phase of the VISTA program ended and continues to serve as a model for government-industry collaboration. In this talk we will discuss the structure of the IC, as well as its accomplishments and current research activities in phase II.

SCD is a leading manufacturer of MWIR InSb Focal Plane Arrays (FPA) with formats up to 3 megapixels. Using photodiode layers grown by Molecular Beam Epitaxy (MBE), the operating temperature is raised to ∼ 100 K, compared with 80 K for our legacy implanted junction technology. Due to the excellent manufacturability of III-V MBE materials, we have extended this approach in the development of our newer High Operating Temperature (HOT) MWIR technologies, all of which are based on XBn and XBp barrier devices which suppress the dark current generated by traps in the depletion layer. As a result we now produce a family of InAsSb XBn FPAs operating at 150 K with a cut-off wavelength of λ_C = 4.2 μm. Formats range between 0.33 megapixels and 5.24 megapixels and our latest "Crane" FPA has a pitch of just 5 μm. These detectors are ideal for 24/7 surveillance and long-range applications, due to large formats, increased HOT cooler reliability and very high atmospheric transmission. For applications requiring HOT full MWIR (HFMW) performance (λ_C = ∼ 4.9 μm), we have explored three approaches, all of which have produced operating temperatures in the range 115 - 125 K with high FPA operability and uniformity. Using a suitable design of buffer layer, we have extended the InAsSb XBn cut-off wavelength while maintaining a high quantum efficiency above 70%. Comparable performance has also been obtained in two lattice matched type II superlattice (T2SL) architectures: XBn InAs/InAsSb and XBp InAs/GaSb. The three technologies give great flexibility in design optimization, and initial production of HFMW detectors is scheduled for mid 2022.

In 2019, IRnova announced the serial production of Oden MW, a reduced SWaP (Size, Weight and Power) integrated detector dewar cooler assembly. Oden MW relies on HOT T2SL array (640 × 512, 15 μm pitch) with full MWIR spectral band coverage (3-5 µm) without compromises on electro-optical performances. Ever since, IRnova maintained significant research efforts to further reduce the SWaP footprint, focusing on increased focal plane operating temperature above 110 K, targeting lower demand for cryocooling power thus further reducing overall power consumption. This has now resulted in small pitch T2SL detector arrays with diffusion limited dark current density, which is approaching the Rule07 with a level of around 6.5 × 10^-6 A/cm² at 150 K and a box quantum efficiency (3-5 μm) as high as 67 %. Excellent performance is demonstrated for 640 × 512, 15 μm pitch FPAs with average temporal NETD and spatial NETD values of 21 mK and 6 mK, respectively, when measured with F/5.5 aperture and 60 Hz frame rate at 140 K. These NETD values are insensitive to the temperature in the 80 K – 140 K range. High uniformity and excellent operability (~ 99.84 %) were also obtained at 140 K. In addition, arrays with 10 μm pitch were fabricated which showed similar dark current values, clearly demonstrating material maturity for the short coming small pitch HD HOT T2SL detectors at IRnova.

We have performed a numerical study of the carrier transport properties in gallium-free strained-balanced InAs/InxAs1-xSb type-II superlattices (T2SL) intended for infrared detector applications. The motivation was to understand whether the performance of T2SL detectors is ultimately limited by fundamental or technological processes. We have employed a rigorous one-dimensional quantum mechanical transport model based on the non-equilibrium Green's function (NEGF) formalism that includes a k.p description of the electronic structure. This approach has allowed us to avoid making any a priori assumptions on the physical mechanism (tunneling, sequential tunneling or hopping) dominating the transport. We find that regardless of its nature and cause, the presence of positional and compositional disorder, introduced inherently during materials growth by layer thickness fluctuations, nonuniform antimony composition and segregation throughout the superlattice stack, significantly affects the vertical carrier transport properties. In particular, the minority carrier hole mobility is fundamentally limited by the nonideal disorder. Furthermore, upon reducing the temperature, holes become fully localized and transport occurs by hopping, which explains published measured photodetector data that demonstrates the quantum efficiency exhibiting a very strong temperature dependence that degrades as the temperature is reduced. We also found that the minority carrier electron mobility is largely unaffected by disorder, indicating the p-type absorbing layer as the preferred option. We have also performed simulations of typical nBn detectors with a simplified NEGF model based on the effective mass approximation and Büttiker-probe self-energies, which also allows us to explore the possibilities offered by quantum-corrected drift-diffusion approaches. We will present simulation examples of representative gallium-containing and gallium-free nBn structures intended for MWIR and LWIR photodetector applications. These examples will include calculations of I-V characteristics, SRH recombination rates and quantum efficiency.

In recent years development focus for higher operating temperatures (HOT) and optimized size, weight and power (SWaP) characteristics has been on MWIR modules at AIM. However, HOT as well as small pixel pitch combined with high spatial and thermal resolution is of great interest for LWIR applications, too, e.g. for scenarios with degraded visual environment. Up to now LWIR detector arrays were manufactured in AIM’s mature planar MCT n/p technology and are typically operated at ~75K. In-depth studies of a p/n pixel structure at AIM showed significant reduction of the dark current and lower noisy pixel levels compared to their n-on-p pendants. Encouraged by these results a p/n pixel polarity is currently introduced to LWIR modules using different detector formats and pitch sizes to optimize performance and to increase operating temperature towards 100K. For VGA-format LWIR detector arrays with 15μm pitch a ROIC with p/n pixel polarity combined with a high charge handling capacity (CHC) of ~14Me- is available. With this approach we strive to increase the operating temperature to enable usage of smaller cooler types. Performance data and benefits in SWaP characteristics are discussed. An HD-format (1280x720 elements) 12µm pitch LWIR-module with NETD values of ~30mK and a high frame rate of 120Hz has already been demonstrated. Now electro-optical performance of LWIR detector arrays having a p/n diode polarity and a cutoff-wavelength of up to ~11μm were characterized. An even smaller pixel pitch of 10µm is currently introduced at AIM for LWIR detector arrays in a XGA-format. For the dedicated ROIC a CHC of ~7Me- was realized enabling high thermal resolution of ~30mK. First performance results and key features of the associated IR-module will be presented.

SWAPc (Size, Weight And Power-cost) is a strong trend in IR imaging systems. It requires focal plane arrays with smaller pixels, operating at high temperatures. For MW systems, the full spectral band (up to 5μm) shows a strong advantage over the blue band (4.1µm) as it maximizes the number of incoming photons from a room temperature scene. Few years ago, LETI and Lynred have been developing 7.5μm pitch MCT arrays in MW full band. The first version of this technology was based on n/p diodes operating at 110K maximum temperature. Switching to p/n using extrinsic doping allows today an important gain in dark current, enabling operating temperature up to 130K or even higher. This paper will describe our latest results in the design and fabrication of such HOT small pitch arrays, starting with test chip arrays, followed by the full the characterization of 1280×1024 7.5μm pitch arrays. First order figure of merit (dark current, QE…) are of course considered, but second order figure of merit will also be discussed such as noise tails.

Leonardo DRS (DRS) has developed High Operating Temperature (HOT) HgCdTe detector material, small-pitch focal plane arrays and ultra-compact Dewar/cooler assemblies. These breakthrough technologies are integrated into a high-definition version of our micro camera core. This report provides an update on the performance, reliability and maturity of the HexaBlu 1280 × 960, 6 μm pitch midwave camera core. The HexaBlu weighs <0.65 lbs., displaces <80 cm³, and achieves a Noise Equivalent Temperature Difference (NETD) of 27 mK at f/2.62 with full well at a 335 K scene. This sensitivity is complemented by a Modulation Transfer Function (MTF) within 2% of theoretical for DRS’s detector architecture. Together, low NETD and high MTF enable sharp longrange imagery. The Camera Core dissipates 4.5 W and achieves cooldown in ~2.5 minutes at 25°C, while providing onboard non-uniformity correction and bad pixel replacement. DRS predicts a mean time between failure of 23,900 hours in an environment cycling between 15°C and 64°C. In ongoing accelerated life testing, the cooler has averaged over 27,000 failure free hours in a 72 hour thermal cycle, and the Dewar has averaged 100,000 failure free hours at ≥70°C ambient. Now in limited rate production, the HexaBlu® leverages 95% design commonality with the Dewar/cooler assembly in fielded weapon sights.

Having established production capacity for high resolution, small pixel Mid Wave Infra-Red (MWIR) devices down to 8μm; this paper discusses the latest developments at Leonardo UK with 12μm MWIR-LWIR Dual Waveband Infra-Red (DWIR) high-performance infrared detectors, grown by Metal Organic Vapour Phase Epitaxy (MOVPE) on GaAs substrates. As with the 30μm, 24μm and 20μm mesa pixels that Leonardo UK pioneered during the early 2000’s, the 12μm devices use a “back-to-back” diode arrangement, whereby the waveband is selected by changing the bias polarity across the diode stack; thus ensuring spatial coherence between the two wavebands. The increased thickness of DWIR MCT compared to single-band material makes manufacturing the mesa structure, in order to control inter-pixel crosstalk increasingly challenging with smaller pixel pitches. Previous publications by Leonardo UK presented results of 12μm DWIR technology on a 24μm Readout Integrated Circuit (ROIC), allowing only 25% of the pixels to be assessed; in this paper, we discuss results of this material on a 12μm ROIC, enabling assessment of 100% of the pixels. Low defects together with near Background Limited Infra-red Photodetector (BLIP) performance demonstrates significant progress towards the manufacture of higher resolution, lower cost DWIR devices by Leonardo UK.

As the largest defense company in Turkey, ASELSAN A.S. pioneers the development of high performance electro-optical systems. Starting from 2014, significant progress has been made for the mid-wave infrared (MWIR) HgCdTe detector technology including development of Cadmium Zinc Telluride (CZT) substrate, Mercury Cadmium Telluride (MCT) growth and focal plane array (FPA) fabrication as well as Readout Integrated Circuit (ROIC) design. In this paper, recent process optimization studies on MWIR MCT detector technology are presented. p-on-n MWIR MCT layers with Cadmium (Cd) composition of ~0.3 are used for the FPA fabrication. 640x512/15 µm FPAs, which demonstrate the state-of-the-art performances, have been fabricated. Typically, over 99.0% operability and less than 25 mK Noise Equivalent Temperature Difference (NETD) values are attained with a cut-off wavelength of 5 µm at 77K. Among these remarkable results, major improvements have been recorded in pixel uniformity, reliability and reproducibility by revisiting process steps. As a result, process yield has been considerably increased.

The HOT of SW, MW, LWIR and VLWIR photodetectors and imagers are highly desirable for different applications such as earth science and astronomy, remote sensing, optical communication, and thermal and medical imaging. The Sb based Materials and gap -engineered Type-II superlattices (T2SLs) has drawn a lot of attention since it was introduced in 1970 by Leo Esaki et al, , for infrared detection as a system of multi‐interacting quantum wells. T2SL material system has experienced incredible improvements in design, gap and atomic engineering, high quality materials , device structure designs and device fabrication process, which elevated the performances of T2SL‐based photodetectors to a comparable or superior level to the state‐of‐the‐ art material systems for infrared detection such as Mercury Cadmium Telluride (MCT). As a pioneer in the field, center for quantum devices (CQD) has been involved in growth, design, characterization, and introduction of Sb based Bulk and T2SL material system for infrared photodetection and imaging from deep UV to THZ . This talk will present the power of Sb based materials innovation for breaking spectral and performance barriers for HOT photodetectors and Imagers from deep UV to THZ. at CQD/NU.

In recent years GaSb-based infrared (IR) photodetector technology has continued to mature, moving from research and development to production-scale manufacturing for a variety of applications. In parallel, maturation of molecular beam epitaxial (MBE) growth of MWIR and LWIR photodetectors has allowed for the ramp to production volumes. Recent developments at IQE have shown that our epitaxial process is not only transferrable to production-scale reactors at the same manufacturing site, but to reactors across IQE production sites. Following the demand for larger focal plane arrays (FPAs), IQE has demonstrated high quality epitaxy grown on GaSb substrates measuring 76.2 mm to 150 mm (3” to 6”) diameter without sacrificing cross-wafer uniformity. IQE’s ability to ramp this process to a production-scale MBE, allowing for 9100 mm wafers per run, has resulted in increased throughput, volume, and yield. The surface morphology of these materials will be measured by Surfscan, AFM, and Nomarski optical microscope; the crystalline properties evaluated via HRXRD; and, using large-area mesa diodes, device performance (dark current, QE, and cutoff wavelength) will be analyzed. Using the same material and device characterization techniques, we will assess the wafer-to-wafer cross-platen uniformity, imperative for high-yield production. Through material and device characterization of each production run, IQE is able to implement statistical process control techniques to improve consistency, yield, and throughput. This will demonstrate the production readiness of IQE’s IR epitaxy.

L3Harris continues to develop, improve and transition HOT MWIR Type II Superlattice (T2SL) technology that was initially developed through the tri-service Vital Infrared Sensor Technology Acceleration (VISTA) program. The T2SL material system provides the opportunity to generate tunable band gaps for creating lattice-matched heterojunction devices and are integral to suppressing sources of dark currents. The unique design of these heterojunction devices to reduce dark current mechanisms enables MWIR FPAs to operate at higher temperatures with increased system level reliability. The evolution of T2SL MWIR detectors at L3Harris in Mason, Ohio has resulted multiple breakthroughs for both technology and manufacturability.

Attollo Engineering specializes in developing small pixel pitch infrared imaging sensors. Small pixel pitch sensors offer opportunities for imaging system SWaP reduction that open up a variety of SWaP-constrained applications that were not previously feasible. The size and weight of the optics also decrease because of the small pixel, enabling further SWaP savings. Attollo Engineering has developed high-definition high-operating-temperature SWIR and MWIR sensors with pixel pitches as small as 5 µm using III-V compound semiconductor detector materials. Additionally, we have developed a compact camera core with an integrated cooler and full featured camera electronics for these imagers.

Effects of gamma and proton irradiation, and of forward bias minority carrier injection, on minority carrier diffusion and photoresponse were investigated for long-wave (LW) and mid-wave (MW) infrared detectors with engineered majoritycarrier barriers. The LWIR detector was a type-II GaSb/InAs strained-layer superlattice pBiBn structure. The MWIR detector was a InAsSb/AlAsSb nBp structure without superlattices. Room temperature gamma irradiations degraded the minority carrier diffusion length of the LWIR structure, and minority carrier injections caused dramatic improvements, though there was little effect from either treatment on photoresponse. For the MWIR detector, effects of room temperature gamma irradiation and injection on minority carrier diffusion and photoresponse were negligible. Subsequently, both types of detectors were subjected to gamma irradiation at 77 K. In-situ photoresponse was unchanged for the LWIR detectors, while that for the MWIR ones decreased 19% after cumulative dose of ~500 krad(Si). Minority carrier injection had no effect on photoresponse for either. The LWIR detector was then subjected to 4 Mrad(Si) of 30 MeV proton irradiation at 77 K, and showed a 35% decrease in photoresponse, but again no effect from forward bias injection. These results suggest that photoresponse of the LWIR detectors is not limited by minority carrier diffusion.

In modern infrared systems, barrier infrared detectors (BIRDs) have been widely used because a barrier is effective in reducing dark current by Shockley-Reed-Hall (SRH) process. Many researches have been studied on design of the barrier that prevents majority carrier flow and permits minority carrier flow. In this paper, we have studied on type-II superlattice (T2SL) nBn detectors having an unipolar barrier, where design and epi. growth are relatively simple for MWIR high operating temperature (HOT) and cooled LWIR detectors. InAs/InAsSb nBn for MWIR detection and InAs/GaSb nBn for LWIR detection were designed and fabricated. The fabricated MWIR and LWIR devices showed a dark current density of ≤ 2×10^-6 A/cm² at 150 K and ≤ 5×10^-6 A/cm² at 80 K, respectively. Also, 15 μm VGA MWIR and LWIR FPAs showed excellent performance with an average noise equivalent temperature difference (NETD) of ≤ 20 mK and operability of 99.5 % at 150 K and 80 K, respectively. MWIR HOT detector exhibited measured NETD similar to theoretical NETD considering dark current. And 10 μm SXGA HOT MWIR detector for high resolution imaging showed perfornance with an average NETD of ≤ 25 mK and operability of ≥99.5 % up to 130 K.

Leonardo DRS is a leader in small pixel uncooled FPA technology with the development of 10μm pixel 640×512 and 10μm pixel 1280×1024 FPA formats. Leonardo DRS offers the Tenum®640 and Tenum®1280 uncooled commercial camera cores based on these FPA formats. The Tenum®640 operates in 60Hz and 9Hz framerate modes with f/1 equivalent NETD sensitivity of <60mK and nominal power dissipation of 1.2W. The Tenum®1280 operates in 30Hz and 9Hz framerate modes with f/1 equivalent NETD sensitivity of <60mK and nominal power dissipation of 2.3W. The Tenum®640 uses a wafer-level vacuum packaged 10µm 640×512 FPA. In this paper, the Leonardo DRS Tenum®640 and Tenum®1280 camera cores will be discussed along with relevant 10µm FPA technology and advances in wafer-level vacuum packaging. In addition, a summary of Leonardo DRS 10µm and 17µm FPA formats in production will be presented. Finally, a broadband IR version of the Tamarisk®640 will be discussed.

Microbolometer detector development and production processes have been studied intensely at ASELSAN for the last several years. Researches have been conducted so as to develop uncooled Focal Plane Arrays (FPAs) with high resolution and smaller pixel pitch. Test results show that SAFIR640 detectors have high performance level and low time constant which make them ideal for military and civilian applications. SAFIR640 microfabrication has been performed on 8’’ CMOS ROIC wafers which are also designed by ASELSAN. A double layer 17 μm pitch microbolometer structure is designed with an active material layer of VOx. 640×480 format SAFIR640 detectors with high TCR and low noise level are successfully fabricated and integrated into a TEC-less system. The produced detectors have low NETD (<30 mK) and low time constant values (<12 ms) values according to the test results. In this paper, electro-optical characterizations and the performance measurements of the SAFIR640 detectors have been presented.

Historically LYNRED (created from the merger of SOFRADIR and ULIS in 2019) has used amorphous silicon materials (“a-Si”) as thermistor materials for its uncooled microbolometer products. If a-Si materials present several advantages that made the success of LYNRED’s products (easy to use and integrate in thermal camera), their intrinsic bolometric performances (i.e. TCR and 1/f noise) are still lower than the commonly used oxides thermistors[1] (i.e. VOx[2] and TiOx[3]). In order to stay in a leading position regarding sensor performances without any trade-off, LYNRED, with the support of its historical R&D partner the CEA-LETI, developed new materials. This strategy has led to new cutting edge products. At the end of 2020 a new 17 µm pixel pitch product (Pico640s[4]), with one of the highest sensor performance reported on the market (typical thermal sensitivity of 25 mK (f/1, 300K, 30Hz)), has been introduced in our product portfolio. We also launched our state of the art 12 µm product range with performances equivalent to our current 17µm product range. More generally, these developments open up new opportunities toward smaller pixel pitch. The symposium presentation and the associated article will present how we have increased the "Signal to Noise Ratio" (SNR) of our products while keeping all the elements which have been our hallmark. Special attention will be paid to NETD, stability of product characteristics during operation and manufacturing excellence. All these features were obtained only by hardware (at the pixel level) improvements without the need to use sophisticated algorithms or specific ROIC functions, in the spirit of LYNRED’s FPA products.

Infrared arrays found their way into widespread applications in various industries. Unlike other array technologies, thermopile arrays allow to build true shutterless radiometric IR cameras. Thermopile arrays with pixel numbers from 8x8, 16x16, 32x32 up to 80x64 were introduced to mass production. In this paper, Heimann Sensor introduces first thermopile arrays with 45 and 60 µm pixel sizes allowing to extend the application range into thermal imaging and surveillance. All necessary signal conditioning and readout electronics including SPI interface are monolithically integrated on the sensor chip. All thermopile arrays and array modules are equipped with an infrared optical lens ranging from 9-12 deg FOV for far distances up to 120x90 deg FOV for ultra-wide field of view; e.g. for screening of hot spots and fire risk. The new higher resolution arrays with 45 or 60 µm pixel size open the door to array formats up to 160x120 pixel in the same TO-8 housing.

The high level of expertise accumulated by Teledyne in designing ROIC for different spectral imaging sensors (from X-rays to far–infrared) enables the company to develop high performance thermal imaging sensors optimized for Size, Weight, Power and Cost (SWaP-C). The specific ROIC design discussed avoids almost any trade-off between scene dynamic range and NETD which is the main issue encountered by all other FPA suppliers. In this paper, we will show how to achieve a NETD of 50mK with a dynamic range higher than 1000°C without any FPA adjustment settings. Key characteristics of the sensitive material are described to highlight the capabilities of this technology for system operation: mainly the ease of operation due to fully digital ROIC and specific design will be demonstrated. Finally, we will see how all the previously mentioned key parameters are paving the way to affordable, powerful thermal imaging modules and cameras.

The scalability of Fraunhofer IMS’s nanotube microbolometer technology for uncooled thermal imaging is demonstrated. Thermal insulation of the microbolometers is realized by means of vertically oriented nanotubes arranged underneath the sensor membrane. Thus, thermal insulation is decoupled from the latter, allowing for a variable scaling of the microbolometer, independently of its thermal insulation. Key parameters as electro-optical responsivity, noise, NETD and thermal time constant are presented for pixel pitches varying between 17 μm, 12 μm, 8.5 μm and 6 μm with the latter value being close to the fundamental optical limit in the LWIR, but full electro-optical functionality being maintained.

We evaluated the possibility of performing temperature measurements using an uncooled infrared focal plane array (IRFPA), consisting of an 8032 array of p-n junction diodes fabricated on a silicon-on-insulator (SOI) substrate (MIR8032B1). We previously reported the sensor design and data collection method for the MIR8032B1 at SPIE in 2021. In this presentation, we describe an aberration correction method and a comparison of different lenses with a high modulation transfer function. We verified the accuracy of the measurements using a shutterless method based on the thermal characteristics of the SOI diodes. Based on the results obtained in the present study, we discuss the applicability of such IRFPAs for temperature measurements.

In this study, room-temperature long-wavelength infrared (LWIR) graphene photodetectors using pyroelectric photosensitizers are demonstrated. The devices comprise graphene-based field-effect transistors with lithium niobate as a pyroelectric photosensitizer. To enhance the photodetector performance, we studied the influence of photosensitizer thickness and ferroelectric polarization direction on the pyroelectric photogating effect. Modulation of the gate current indicates that the IR photoresponse is considerably amplified by thick photosensitizers in which dielectric polarization occurs in the direction perpendicular to the graphene channel. The results will contribute to the development of high-performance graphene LWIR image sensors.

We theoretically propose van der Waals (vdW) heterostructure-based wavelength selective infrared (IR) photodetectors using plasmonic metasurfaces (PMs), consisting of top micropatches, graphene on a hexagonal boron nitride (hBN) vdW heterostructure layer, and a bottom reflector. The hBN ensures the vdW heterostructures maintain high carrier mobility in the graphene. The wavelength selective detection of the graphene can be controlled mainly by the micropatch size over a wide range from the middle- to long-wavelength IR regions. The wavelength can also be electrically tuned by the chemical potential of the graphene. These results will contribute to developing high-performance wavelength tunable graphene/hBN-based IR photodetectors.

This presentation will describe the development of of the first MEMS microbolometer at the Australian Defence Science and Technology Organisation

As the value of assets in space increases, the need for protection from internal system faults and fires becomes necessary. The rapid nature of commercial space advancement contrasts the approach NASA utilized, and there is a paramount need for a Federal Aviation Administration (FAA) approved commercial off the shelf (COTS) solution to fire detection in space. Our objective is to develop a low size weight and power (SWaP) solution for an early fire detection system implemented as an industry standard. This work highlights the electrical systems which drive LED-based absorption spectroscopy earlyfire detection sensor which targets CO and CO2. The unit’s core logic is executed using a PIC24HJ series microcontroller with custom libraries that interface with several devices through analog, I2C, and SPI communication protocols. The prototype unit is slated for an upcoming sub-orbital flight test which will record and log measurements data onto a microSD card for subsequent post-flight analysis.

As the expansion of maneuvers, assets, and access into space increases, the risk of fire aboard a spacecraft or other vessel becomes an unavoidable concern. There is an inability of existing technology to detect fire and concerns with the limited types of combustible materials which can be sensed rapidly. To better position the growth of this economic sector, there is a need to ensure rapidly implementable and standardized components which can address this common need across flight and mission platforms. This work is about developing the optical system for an LED-based absorption spectroscopy, an early-fire detection sensor that identifies CO and CO₂. The proposed design consists of restricted LED emitters with corresponding spectral bandpass filters along each beam path for CO₂ and CO, respectively.

Detection, identification, and quantification of exhaust gas emissions is critical to ensure compliance with regulatory guidelines and mitigate damage to the environment. Passive thermal infrared hyperspectral imaging is among the technical solutions that can remotely detect, identify, and quantify multiple gases simultaneously. Telops has recently developed a suite of gas quantification tools designed for use on the Hyper-Cam series of hyperspectral imaging systems. In order to demonstrate the feasibility of quantitative gas measurements in real-world environments, Telops participated in a maritime measurement campaign in 2021. The Telops Hyper-Cam-LW was used to quantitatively measure the SO2 emissions from the main exhaust of a cargo ship transiting the Saint Lawrence Seaway. This work will introduce the fundamental principles underlying gas quantitation using thermal infrared hyperspectral imaging as well as report quantitative gas imaging results generated from the 2021 measurement campaign.

We present an approach to automatic visible light/infrared (VL/IR) image registration that leverages multiple visible light apertures for fast computation on resource-constrained systems. VL/IR registration is computationally challenging due to the different modalities of image generation. Although feature-based algorithms for direct registration exist, these methods proved too complex to reliably perform registration on low-cost, embedded processors in real time. We instead employed a second VL camera to dynamically estimate 2D translations aligning the brightest (warmest) objects in the IR video stream with their counterparts in the first VL video stream. Regions of interest are first selected based on the brightest areas in the IR image, as our application is primarily concerned with detecting objects warmer than background. The same broad region - e.g. the lower-left quadrant of the frame - is then selected in the VL1 and VL2 images. The translation that best registers the first VL ROI to the second is estimated through template matching. Because all apertures in our camera system are fixed and coplanar relative to one another, the translation that best aligns the IR ROI to the VL1 ROI can be estimated from the translation from the VL2 ROI to the VL1 ROI. This approach provides dynamic registration of 1080P video at upwards of 10Hz on an ODROID-XU4 single-board computer, while also allowing the processor time to render the IR-augmented video stream at 20Hz. Imagery collected using Deep Analytics’ IR Boom Camera will be presented to demonstrate the approach.

The advantage of shortwave infrared (SWIR) imaging for reconnaissance tasks and the detection of camouflaged objects are known and demonstrated. The realization with an integrated visual and shortwave camera and discrimination with a four-filter shortwave colorimetry of camouflage objects was shown. Multispectral images are captured using four appropriate bandpass filters in a filter wheel and contrast was optimized by a tunable generic bandpass filter based on principal component analysis (PCA). Based on this experience, it is demonstrated that SWIR multispectral imaging can provide longer observation ranges compared to color imaging although the pixels of color cameras are significantly smaller, resulting in higher spatial resolution.

Airborne meteorological instruments are key to climate science, of which understanding cloud formation is an important component. Cloud formation involves the entrainment of air with dissimilar convective, thermal, and humidity properties. Improved understanding of these meteorological parameters can improve forecasting. The National Oceanic and Atmospheric Administration (NOAA) currently relies on outboard sensors with 25 Hz sampling, giving 10 m spatial resolution during nominal fixed wing aircraft flights. Higher-resolution humidity and temperature data are needed. We describe a novel laser absorption-based instrument that can make high sensitivity airborne measurements with 25 cm spatial resolution. The use of mid-infrared (MIR) quantum cascade lasers (QCLs) enables high sensitivity humidity measurements based on strong fundamental vibrations of water vapor. Sampling at 1 MHz (averaged data output exceeding 1 kHz) enables the high spatial resolution from a jet platform that accesses near the ground to 45,000 ft. This technology could be extended using complementary lasers to identify any Chemical, Biological, Radiological, and Nuclear (CBRN) threats, or hazardous material incidents, based on their MIR absorption features. Additional applications could also include highly accurate information for combating wildfires and high-speed identification of anomalous gas-phase species in semiconductor processing.

Thermoelectrically coupled nanoantennas (TECNAs) are fast thermal sensors for the mid- to far-IR regime. TECNAs resonantly absorb EM radiation using a nanoantenna and nanothermocouple, and can be made directionally sensitive using a reflecting cavity. We present TECNAs located above a cavity etched into a substrate to determine angle of incidence of laser beams. The position of the antennas relative to the cavity center provides beam steering capability. We show in simulations that radiation and receiving characteristics of TECNAs are strongly dependent on position above the cavity. Positioning multiple antennas above a cavity provides angle-of-incidence resolution capability in the thermal infrared.

Since the rise of deep learning (DL), methods are being proposed daily for all kinds of applications such as systems that include radar, infrared (IR), and electro-optical (EO) imagery. The most common DL application uses the convolutional neural network (CNN) for visual (VIS) imagery as data sets are available for training. This paper highlights recent advances of DL for Infrared (IR) applications by conducting a literature review for IR only and IR plus another modality (e.g., Visual+IR). For IR DL developments, the paper examines that of (1) applications (medical, non-destructive evaluation, target recognition), (2) sensing (space, air, ground), and (3) multi-modal (transfer learning, image enhancement, band selection); while determining aspects for improving the IR sensor design.

Recent advances and ubiquity of Unmanned Aerial System (UAS) capabilities have expedited the need for counter UAS capabilities. While visible imaging and acoustic sensors have been widely used to detect/track UAS signatures, several challenges remain: (1) images that are acquired using EO sensors that are sensitive to visible light (0.4-0.7μm) contain a significant amount of clutter leading to false detections and have limited feasibility under low variable lighting condition (e.g., nighttime), (2) visible imagery is more susceptible to nonlinear, time varying atmospheric distortions, and (3) the discriminative power spectrum of UAS acoustic signatures are sensitive to amplifier gains, microphone array directional response characteristics, and obfuscation by non-white acoustic clutter/noise. Instead, we consider using thermal infrared—specifically longwave infrared (7-14μm)— cameras to detect UAS platforms. Additionally, we consider detecting UAS platforms using a UAS-based counter surveillance platform equipped with the thermal infrared imaging payload, opposed to conventional ground-based counter UAS imaging systems. Here, challenges arise from limited discriminative details and quality in thermal imagery (compared with visible imagery) due variations in sensors, standoff distance, and motion. Therefore, we present a new dataset containing both thermal and visible imagery designed to evaluate UAS detection performance using existing object detectors, such as YOLOv5,1 RetinaNet,2, 3 and SSD.4 More importantly, we present a novel deep domain adaptive framework to optimize the object detectors for more discriminative detection performance and to enhance both daytime and nighttime operations. Lastly, we provide extensive analysis that compares our framework to state-of-the-art domain adaptation methods using our dataset.

The current de-facto Automotive Driver Assist System (ADAS) sensor suite typically comprises mutually dependent visible-light cameras and radar, but when one of these sensors becomes ineffective, so too does the entire sensor suite. This scenario happens often especially when it comes to pedestrians, cyclists, and animals at night or in inclement weather. We will discuss a novel modality known as monocular 3D Thermal Ranging™ that dramatically improves pedestrian safety to reduce accidents and save lives. The solution is based on custom HD thermal imaging and innovative AI based computer vision algorithms. Operating in the thermal spectrum these algorithms exploit angular, temporal and intensity data to produce ultra-dense point clouds (up to 150x that of LIDAR) along with highly refined classification for object detection and identification. We will discuss how to derive ultra-high-density range maps from a monocular thermal camera running a purpose-built AI CNN and bespoke embedded optics. The resulting new sensor modality provides all the benefits of a thermal camera, including all weather and day/night operation and instant detection of animals and vehicles, while simultaneously delivering a geospatially registered 3D range map of such density that perception stacks may enjoy unprecedented awareness. This new sensor maybe an ideal complement to the ADAS & AV sensor suite where thermal perception is sorely needed and the redundancy of real time imaging and ranging channels will be most welcome to improve the utility, comfort, and safety of autonomous and semi-autonomous vehicles.

Infrared thermography is a non-invasive technique that records temperature patterns of the body which can be used as an adjunct method for the detection of diverse medical pathologies. One limitation of medical thermology is incomplete coherence to a standardized interpretation procedure which can lead to disparity of results given by different interpreters. Artificial Intelligence and deep learning models have been used for pattern recognition and classification of objects and have been adopted elsewhere as an adjunct methodology in medical imaging diagnosis. To perform deep learning algorithms a large database of infrared thermographic images must be put together. These images likely will come from different clinics, use different imaging systems, and they are saved in different proprietary formats depending on the imager used. To circumvent these difficulties a standard format for saving medical thermology studies must be implemented. In this talk the efforts of the American Academy of Thermology (AAT) are presented to standardize a Digital Imaging and Communication in Medicine (DICOM) file format for medical thermology. Also, efforts to implement a Picture Archiving and Communication System (PACS) Software to handle large number of images for thermography big data applications will be presented. Artificial Intelligence applications towards adjunct detection of breast pathologies using infrared thermography will be discussed.

As it becoming more and more reliable and mature, the technology of face recognition has been widely applied to nowadays life. However, conventionally, face recognition uses the visible light as the imaging spectrum and is thus limited under lighting conditions (such as nighttime) and bad atmospheric conditions (such as rain, fog). Infrared face imaging provides an alternative solution to above problem. Nonetheless, infrared (IR) facial images are usually in low quality due to limitation of current imaging devices as well as atmospheric noises and disturbance. This situation restrains the face recognition system from performing well. Therefore, enhancing of low-quality IR facial images is crucial to a practical IR face recognition system. We in this research work propose to address the problem of IR facial image enhancement by a succession of IR facial denoising and IR facial deblurring. The former is realized via a deep neural network of denoising while the latter is achieved by a blind deconvolution algorithm. The denoising DNN is trained on the Waterloo Exploration database and tested on our multispectral face dataset. The metrics of PSNR and running time are used to compare between different denoising methods including both traditional ones and deep learning-based ones. The metric of Tenegrad is used to evaluate the deblurring method involved. Overall, image quality is improved significantly, which in turn proves our proposed framework of successive IR face enhancement to be beneficial.

Deep Learning algorithms have been widely used for different surveillance tasks in recent years, including people monitoring and counting, abnormal behavior identification, and video segmentation. In most situations, it is assumed that the input images are of high visual quality to provide good performance. When the input data is degraded by variables such as high noise or poor lighting conditions accuracy may degrade. We address the illumination issue in this paper by adapting a face recognition algorithm to near-infrared and thermal images. In this study, we propose a fine-tuning approach to allow deep CNN models to be applied to infrared face recognition (NIR and thermal spectrum). The obtained results with the proposed architecture and infrared images show promising results in deep face recognition with a VAR of 96.68% for the NIR dataset and a VAR of 94.57% for the thermal dataset.

High resolution, wide field-of-view, infrared (IR) imagers find use in defense and civilian applications. The most demanding of them desire uniform sensitivity across an image’s field of view, while maintaining a small and light-weight optical design. These attributes can be achieved by curving of the focal plane array to reduce the need for field curvature correction. Using experimental and numerical methods, we investigated the spherical curving of hybridized arrays to demonstrate mechanical feasibility and opto-electronic performance. Each hybridized array comprised a 4k x 4k, 10 μm pixel pitch, midwave IR (MWIR) detector hybridized to a 67 mm diagonal fanout chip. We curve an array to 139.2 mm radius of curvature, resulting in a pixel area coverage of 0.086 sr. Measurements across the curved array revealed minimal variation in bandgap (<0.1 μm) and no appreciable difference in dark current.

Quantum well infrared photodetector (QWIP) technology is an established solution for tactical imaging in the longwave infrared (LWIR), thanks to its unmatched image uniformity, stability and pixel operability (typically >99.9 %). In this paper, we demonstrate that these qualities also make it a versatile platform for other advanced detection applications in this spectral range. First, the development of dual-band (10 and 10.8 µm) QWIP IDDCA as part of the technology demonstrator LisR [1] onboard the International Space Station (ISS) is followed up. Second, enhancement of the object detection in the field studies using polarimetric QWIP imager is presented. Finally, the manufacturability of QWIP focal plane arrays (FPAs) is illustrated by showing the performance statistics from the production of the large-area (16×12 mm² ) and the small-pitch (15 μm) FPAs and uniformity of their characteristics over 4” detector wafers.

Cyan Systems has developed and made multiple improvements on our small pixel camera performance including low noise and compact size, weight, and power. The associated camera components demonstrate key resolution and enabling capabilities. Performance data from compact our new small pixel broadband full high-definition (1920x1080) camera technology is presented. We also report on recent results from our new digital readout integrated circuit (DROIC) small pixel mid-wave infrared camera with an ultra high-defintion (3840x2160) format.

A 10μm pixel pitch 1280×1024 Readout Integrated Circuit (ROIC) for MWIR applications is designed and fabricated using 0.18 μm CMOS process. It operates in snapshot mode supporting both Integrate-Then-Read (ITR) and IntegratedWhile-Read (IWR) configurations. The ROIC pixel has direct injection (DI) input stage and provides 2-bit programmable pixel gain. It has a minimum charge capacity of 0.7 Mé and a maximum full-well-capacity (FWC) of more than 6.3 Mé in ITR mode. 4, 8 and 16 analog video output modes are also supported with a maximum frame rate of 120 fps at 16-output mode. All digital timing and analog biasing are programmable through a serial interface. Integration time is programmable with 0.1 μs resolution by internal timing circuitry. It supports binning, windowing and antiblooming functions. The ROIC operates with 3.3 V and 1.8 V supplies and dissipates less than 175 mW in 4-output mode of operation at 30 fps. An Analog-Front-End (AFE) card is designed to operate the ROIC and convert analog video outputs into 14-bit digital value. Digitized video data is further processed by 1-point and 2-point Non-Uniformity Correction (NUC), histogram equalization and bad pixel replacement algorithms. The ROIC has been tested with a prototype FPA at 77K. Measurement results of ASEL128010 indicate that it is functional at all operating modes including windowing and binning. The input referred noise level of the ROIC is 877 é at 6.3 Mé FWC.

In-situ surface treatment of vicinal Ge substrates provide a modified surface kinetic regime in which PbSe thin films form highly ordered 3D nanoparticles that coalesce to form bulk monocrystalline PbSe films. Doping of PbSe films forms a strong p-n heterojunction with the p-Ge substrates, resulting in a natural dual-band photovoltaic detector structure with low measured reverse bias current density. In-situ RHEED measurements show the growth evolution of PbSe films under varying conditions, with the ability to form high quality bulk monocrystalline PbSe films >1µm directly on mismatched Ge(100) & (111) substrates. While PbSe and Ge showcase a large lattice mismatch (8.2%) and thermal expansion coefficient mismatch (328%), the resulting structure is a crack-free monocrystalline PbSe film with low x-ray diffraction (XRD) full-width half maximum (FWHM) and strong Photoluminescence (PL) spectra.

Intra-frame high dynamic range (HDR) infrared imaging is accomplished in a 1280 x 720 format, 8 um pixel pitch digital readout integrated circuit (DROIC) by spatially combining neighboring pixels with different integration times to obtain HDR pixels. Intra-frame HDR imaging achieves the same level of dynamic range improvement as traditional inter-frame HDR imaging without compromising temporal resolution. Proximal interpolation to retain the spatial resolution of the HDR infrared frame, tone mapping to effectively display HDR infrared content on limited dynamic range displays, and pseudo-coloring to better visualize HDR infrared imagery are discussed.

Ensuring the operating temperature regime of optoelectronic (EO) components, such as detectors and emitters, is paramount for the accurate performance of any instrument comprised of, or relies on, those devices. The semiconductors’ band gaps enable the photoelectric conversion to dilate as a function of temperature, on the order of magnitude variation per 10°C near 300K. Semiconductor infrared (IR) detectors benefit from compact cooling with thermoelectric coolers (TECs), which rely on the Peltier Effect and an input current direction to force heat flow to/from the device to which they are attached. When coupled with a closed-loop control system, this bi-directional capability can enable temperature stability on the order of 0.01°C of the regulated device. Heat sinks and thermally conductive adhesives are required to facilitate the TEC to source and sink heat with the environment. In aerospace applications, it is necessary to design a compact cooling fin architecture that maximizes heat transfer capabilities within a given envelope of system size, weight, and power (SWaP) limitations. These design envelopes persist where an operating environment requires atypical radiation and convection heat transfer consideration. This paper compares two different wire mesh models and assesses their ability to assist in a TEC’s ability to cool an IR detector. Commercial finite element software, Siemens NX, and Simcenter Thermal are used to explore how two different meshes perform in steady-state operating conditions comparing reduced convection coefficients attributable to microgravity and radiative heat dissipation.

Herein, we developed a high-performance graphene/InSb heterojunction mid-infrared (IR) photogated diode for IR image sensors. We achieved low noise owing to a significant reduction in the dark current and high responsivity, which is attributed to the graphene/InSb heterojunction diode structure and the photogating effect. The detection performance of the proposed device is better than that of conventional graphene-based IR sensors in the mid-infrared region of 3–5 μm. These results indicate that the combination of a simple graphene/InSb heterojunction and the photogating effect can produce IR image sensors with better detection performance than existing IR sensors.

Quantum efficiency (QE) is a important parameter of infrared detector. InAs/GaSb T2SL LWIR detector has a low QE due to a small absorption coefficient compared to MCT detector. The QE can be generally increased by thickening the absorber layer but a thick absorber layer increases dark current. In this work, the QE of the InAs/GaSb T2SL LWIR photodetector was improved by Fabry-Perot resonance phenomenon. Resonance cavity is formed between front side metal and backside semiconductor-air interface mirror. At a specific wavelength, the QE is periodically increased by the resonance cavity. To broaden the resonant wavelength band, a grid pattern was formed on the backside of the detector. Consequently, the average QE of T2SL LWIR detector was improved up to ~33 % in the entire 7-9 m wavelength.

We report the investigations of Ge-Si-Sn-O alloys for using them as the sensing layer of microbolometers. The investigated properties include atomic composition, resistivity, temperature coefficient of resistance (TCR), activation energy, transmittance, absorptance and reflectance, optical bandgap and thermal conductivity. We have prepared thin films of GeSi-Sn-O alloys using a combination of direct current (DC) and radio frequency (RF) magnetron sputtering. We bonded pieces of Si substrate on a Ge target by silver paste to obtain a compound Si-Ge target. Si-Ge and Sn were sputtered simultaneously in a Kurt J. Leskar Pro Line PVD-75 sputtering system in Ar+O₂ environment to prepare Ge-Si-Sn-O films. The sputtering power and process gases’ concentrations were varied to obtain appropriate film compositions. Samples were fabricated in a single batch for different tests so that uniform composition and film properties were ensured throughout the samples being analyzed. A room temperature TCR of -3.66%/K and resistivity of 1.885×10⁵ Ω-cm was obtained from the thin film with an atomic composition of Ge₃₉Si₀₅Sn₁₄O₃₆. We also obtained the thermal conductivity of 0.403 Wm^-1 K^-1 for 1339 nm-thick Ge₃₉Si₀₅Sn₁₄O₃₆ film. During our investigation, we found that as the Sn concentration in Ge-Si-Sn-O increased, the absorption also increased. This increased absorption led to decrease the optical bandgap of Ge-Si-Sn-O. Higher Sn concentrations in Ge-Si-Sn-O tend to decrease the resistivity as well TCR. Higher O₂ concentration in Ge-Si-Sn-O, increased the optical bandgap, resistivity and TCR. We also obtained the thermal conductivity of 0.403 Wm^-1 K^-1 for 1339 nm-thick Ge₃₉Si₀₅Sn₁₄O₃₆ film at 300K.

We demonstrate the use of an active hyperspectral sensor for detection and recognition of persons in snowy foliage. The sensor employs a tunable broadband supercontinuum light source for remote spectrum measurement. An algorithm based on support vector machines is used in real-time to classify the object, from which the supercontinuum laser pulse scattered. We present results for person detection during simulated illegal border cross activities in snowy terrain.

Hydrogen-bonding plays an important role in interactions of molecular structures, and is associated with distinct features in vibrational spectra of molecular systems. Interpretation of these features is essential for monitoring and control of structural changes and kinetic processes in large ensembles of molecular structures. Computational experiments based on molecular dynamics provide interpretation of vibrational-spectrum features. This report extends previously reported simulations concerning nerve-agent-sorbent binding for examination of spectral features correlated with annealing

Graphene, an atomically thin carbon sheet with a two-dimensional hexagonal lattice structure, has attracted attention because of its unique electronic and optical properties. Graphene has two promising optical applications: graphene photodetectors that can operate at various wavelengths, and resistive graphene sheets whose optical constants can be configured via an applied voltage. In particular, graphene is a candidate for plasmonic metamaterial absorbers and emitters because of its electrical tunability. We previously demonstrated the concept of multilayer graphene-based metasurfaces. In the present study, we developed a more accurate theoretical calculation model for graphene, and theoretically investigated graphene nanoribbon metasurface absorbers (GNRMAs) for single- or multi-band infrared detection. The GNRMAs consist of a top periodic graphene nanoribbon layer formed on a dielectric layer, which contains another periodic graphene nanoribbon layer and is formed on a back-reflector. High wavelength-selective absorption can be achieved because of the surface plasmon resonance (SPR) of the graphene nanoribbons and Fabry– Pérot resonance of the dielectric layer. The wavelength of graphene SPR is determined mainly by the width of the graphene nanoribbon. The absorption wavelength can be electrically tuned via the chemical potential of graphene, which can be controlled by the voltage applied to the graphene nanoribbons. The gap between the graphene nanoribbon layers determines whether the absorption is single-band or multi-band. This electrical tunability can be enhanced by independently controlling the voltage applied to each graphene nanoribbon layer. These results will contribute to the development of electrically tunable graphene-based multispectral infrared detectors and emitters.