Sensors Unlimited Inc. (SUI), a Raytheon Company, continues to expand its sensor portfolio through the development of time-of-flight (TOF) capable technologies. The utility of SWIR for active TOF solutions is of particular interest due to its inherent eye safety characteristic. SUI is developing TOF technologies both at the detector and readout integrated circuit (ROIC) layers of the focal plane array (FPA). In this work, SUI will offer updates to the internal development efforts comprising both areas as it pertains to the time-of-flight technologies.

In this work, SUI presents an update on PIN Photodiode Array (PDA) developments and the advancements in Avalanche Photodetectors (APD) Array development. SUI continue to push the PIN based SWIR photodetector performance by reducing the dark current, increasing the quantum efficiency in broad spectral wavelength range from 400nm to 1700nm and extending the wavelength to 2.6μm. We will also present APD technology advancements specifically related to low temperature performance from room temperature to 260K and Geiger Mode operation. In addition, we will discuss the requirements of Readout Integrated Circuits (ROIC) for APD based sensor development for synchronous and asynchronous pulse detection and active and passive quenching mechanisms. We will also discuss 2-D and 3-D TCAD simulation results at low temperature and compare them with measured performance results. Finally, recent results related to the advanced development of Geiger Mode Avalanche Photodetectors (GMAPD) and the results using passive and active quenching circuits are presented.

Over the last decade a growing demand for imaging solutions in the short wave infra-red (SWIR) regime has stimulated technological investments aimed for cost and size reduction. This resulted in the development of smaller pitch, lower power focal-plane arrays (FPAs), enabling the production of a very compact and low-cost electrooptical systems for the SWIR band. SCD has been on the forefront of this technological wave developing the SWIFT family of 10 μm pitch InGaAs SWIR digital infrared detectors.

Currently the SWIFT family consists of two products. The SWIFT 640 is a compact VGA version of the Cardinal1280 FPA embedded in a compact ceramic package. The module consists of dedicated proximity electronics boards providing power and timing to the readout circuit (ROIC) and enables communication and video to the system. It presents low noise imaging with very low dark current and excellent imaging under low light level conditions. In this work, we will elaborate on the electro-optical performance, low SWaP design considerations and the environmental endurance of this module.

The second product – SWIFT 640 EI – combines daylight and low light level imaging with event-based imaging and multi spot laser tracking. Recently we described the architecture, key features, and preliminary characterization results. In this article, we will present detailed results for the ALPD detection sensitivity and false alarm rate (FAR) as a function of laser pulse intensity and background flux. We will also present our capability to track and decode simultaneously several laser spots.

In recent years, an interest in the detection of the Short Wave Infra-Red (SWIR) band has grown. In these wavelengths, we benefit both from the properties of the visible and thermal infrared, offering new information and a different contrast to the image. In the defense field, this band offers the possibility of passive and active imaging, as well as the detection of laser or thermal radiation from bodies above ambient temperature. The state-of-the-art III-V detectors in the SWIR are InGaAs photodiodes on InP substrate that are limited by a 1.7 μm cut-off wavelength. Super-lattice (SL) based detectors, that have been increasingly studied in recent years, make it possible to reach new cut-off wavelengths. Starting from the InGaAs on InP detector technology that has been mastered for more than ten years by THALES, the III-V Lab we propose to extend the detection range beyond 1.7 μm by introducing a SL in the active region of an InGaAs photodiode. We will present the results obtained up to 2.5 μm, as well as the solutions implemented to limit the carrier localization in the super-lattice and the associated QE degradation.

ASELSAN has made significant progress on developing its short-wave infrared (SWIR) technology, with a focus on improving dark current, quantum efficiency, and operability. In recent work, shunt current and generation-recombination current have been identified as the predominant dark current mechanisms. Shunt current can be suppressed by reducing the dangling bond count which requires optimizing the focal plane array passivation, and generation-recombination current can be reduced by improving the device design. Extensive work on process optimization employing various passivation schemes combined with theoretical layer design has lowered the SWIR focal plane array pixel dark current values down to < 1 nA/cm². Furthermore, achieving low dark current without sacrificing high quantum efficiency (exceeding 80%), by building on the previous process and post-process work, has enhanced the sensor’s ability to capture faint signals. 640x512 format and 15 μm pitch SWIR focal plane arrays coupled with ASEL64015CG read-out circuits have consistently reached > 99.9% operability. After maturing the development work, ASELSAN launches its SWIR detector, LEOP-640/15-SW, pioneering the company’s photodetector production. In this paper, the results of the theoretical and experimental R and D work on LEOP photodetector development and production at ASELSAN are presented.

The value proposition for Short-Wave Infrared (SWIR) includes capabilities beyond standard passive, low-noise imaging. Sensors Unlimited Inc. (SUI), a Raytheon Technologies Company, has expanded its multi-mode tracking (MMT) portfolio with the development of two new solutions, each of which offers laser range finding (LRF) capability. The SWIR Pocket Scope-MMT (SPS-MMT) sets the gold standard for asynchronous laser pulse detection (ALPD) and low-noise passive imaging, internally dubbed MMT, in a SWIR hand-held solution. SUI’s expanded portfolio now includes a variant of that product with an embedded LRF so that the warfighter can simultaneously, image, track and decode any laser designators, and determine the distance to any targets in the same scene of interest. Additionally, SUI has developed an HD version of that capability set. Performance results of each solution will be described herein.

As customer demand for infrared laser sensors increases, so too does the need for low cost, readily manufacturable SWIR imaging systems capable of asynchronous laser pulse detection (ALPD). Sensors Unlimited, Inc., an RTX company, presents recent advancements in its SWIR APLD products tailored toward high volume production and broad deployment. Detectors based on SUI’s multi-mode tracking (MMT) readout integrated circuit (ROIC) have been adapted for uncooled operation over a wide temperature range, enabling the elimination of costly thermoelectric cooling. A chip-on-board device configuration has also been implemented, obviating the need for a windowed package. Automation of fabrication processes further reduces unit cost and provides improved device uniformity. Results of SUI’s latest system performance assessments are also discussed.

Leonardo UK high performance short waveband infrared Avalanche Photo Diode (APD) array technology is being developed for high-speed 2D linear mode photon counting, active imaging and other low flux or pulse receiver applications. APD arrays have been re-engineered for high speed and sensitivity, and fabricated in HgCdTe (MCT) using Metal Organic Vapour Phase Epitaxy (MOVPE) grown on low cost gallium arsenide (GaAs) substrates. MOVPE enables precise band gap engineering of the MCT heterostructure to implement designs that can suppress dark current, and achieve high APD gain and wide spectral responsivity at the required operating temperature. Such array structures incorporate a proprietary back plane to help reduce sensitivity of the array to de-bias or time constant effects that can otherwise reduce sensitivity, dynamic photo response, or introduce cross talk effects across the array. This paper reports technical progress and preliminary results. Array characteristics have been determined. Measuring attenuated laser pulses, a high-speed 2D array has been evaluated using a 500 ns gate. The sensor’s pixel output values settle to discrete bands pulse to pulse. A histogram of the values over the range 0 – 10 photons shows a characteristic Poissonian form indicating high-speed linear mode photon counting sensitivity. Future developments are identified.

A number of studies suggest that the Short Wave InfraRed (SWIR) band (0.9-1.7μm), offers a significant advantage over the visible for long-range daytime scenarios. This advantage of SWIR is due in particular to its excellent optical penetration in the presence of aerosols thanks to reduced light-scattering effects, allowing good scene contrast to be maintained over very long distances. This study reports the results of a field evaluation campaign, involving Lynred’s SNAKE TECLESS (TL) sensor (640x512@15μm, InGaAs) along size narrow field optics. This year-long campaign features a variety of atmospheric conditions, weathers and aerosol types. Those targets are at distances ranging between 10km and 84km. Finally, we compare the image obtained with SWIR sensors having a pixel pitch of 15μm and 10μm, with the same objective lenses, in order to conclude on the interest of reducing the pixel pitch for a gain in range.

SWIR imagers are seeing wide use in commercial and defense applications. The conventional choice for the detector is InGaAs lattice-matched to InP. Recently, colloidal quantum dots using PbS have shown promise as a SWIR responsive material. CQDs have the promise or reducing SWIR sensors cost substantially, but the performance difference requires more characterization. We demonstrate both InGaAs and CQDs in focal plane arrays using the same ROIC, the AE1702, which is a 640x512 format ROIC with a 5 μm pixel pitch. We, show spectra, PTC measurements, and imaging. In addition, we show measurements using 1900 nm CQDs-based FPAs.

Colloidal Quantum Dots (CQD) made of inorganic heavy atoms with low frequency vibrations should facilitate long lived excited electronic states. This should allow CQDs to unlock the previously theorized great potential of quantum dot for infrared technologies. Using different starting semiconductor material, CQDs with interband or intraband transitions have been shown to cover the full infrared spectrum. Single element detectors have been realized from the near-IR to the LWIR. There is also a growing number of demonstrations of focal plane arrays with such materials, in the SWIR with PbS, and MWIR with HgTe. LED demonstrations cover the near-IR and are recently extending into the MWIR. This talk will describe the progress to date of CQD optoelectronic devices in the MWIR, as well the main target and challenges.

Using colloidal quantum dot (CQD) technology, SWIR Vision Systems has developed a 6MP SWIR and e-SWIR FPA. The uncooled 3072-by-2048-pixel sensor uses a 7µm pitch to balance sensor size, signal-to-noise, and on-chip capabilities. The 6MP sensors also leverage an improved fabrication process, resulting in a 2-3X increase in QE over the existing CQD product line. The uncooled 6MP focal planes will be integrated into two distinct camera formats: fixed platform and DSLR. Both types accommodate C and M42 lens mounts, feature 100Hz speeds with 12-bit resolution, and will be offered in standard SWIR and extended SWIR ranges (400-1700 nm and 350-2100 nm, respectively). The fixed platform format features a reduced footprint, CoaXPress or 10GigE interfaces, and GenICam compliance. The DSLR format is a battery-powered DSLR-style camera that includes a touchscreen, image and video capture, and onboard storage. For outdoor use, this camera will be IP65 rated and ruggedized.

Image sensors made using colloidal quantum dots (CQDs) as the optical absorber material are breaking through as a viable competing technology within the SWIR and MWIR imaging domains. The CQD-based absorber material stack is processed directly onto the surface of the CMOS wafer providing advantages in scalability, cost and flexibility regarding pixel size and dimensions. The absorption spectrum can be tailored by choice of quantum dot size and material system for the same underlying read-out integrated circuit (ROIC). Here, we introduce the Emberion image sensor platform and report our recent results on image sensor development using Lead Sulfide (PbS) CQDs processed onto our custom-designed ROIC. The optoelectronic characteristics of the CQD photosensitive stack are analyzed and the optimal interface to the ROIC is discussed. We also address challenges related to manufacturability such as the planarity requirements of the ROIC surface to facilitate wet-processing via spin-cast CQD thin-film layers. We demonstrate wavelength response from 400 nm out to beyond 2000 nm with noise equivalent irradiance (NEI) below 1e-3 W/m2 over the entire spectral range. Selected illustrative application demonstrations are showcased including detection of water content at SWIR wavelengths, high-speed imaging of a moving target at 400 fps and camouflage detection.

AIM as one of the global leaders in higher operating temperatures (HOT) mercury cadmium telluride (MCT)-based infrared detectors presents its status on small pixel pitch short wavelength infrared (SWIR), mid wavelength infrared (MWIR), long wavelength infrared (LWIR) and very long wavelength infrared (VLWIR) focal plane detector arrays (FPA) and gives a glimpse of the near future in the field. As of now, pixel operabilities exceeding 99.7% and excellent radiometric performance are attained in the measurement under typical operating conditions and at increased detector operating temperatures of 235K in the SWIR, 170K in the MWIR, 110K in the LWIR, and 70K in the VLWIR. Pixel pitches range between 7.5μm and 15μm. Thus, infrared applications with reduced size, weight, power dissipation and cost can be served. We outline the essential technological contributions of material science and device processing making this evolutionary step possible.

In this contribution, we will present a finite element method modelling study for the optimization of QE in LWIR InAs/GaSb type-II superlattice detectors via the employment of metastructures. Experiments to realize these devices will also be presented. In our approach, the average integrated QE for a structure with an absorber thickness of 2.1 µm is theoretically improved from 35% to 73%, corresponding to an improvement of 108%. For a detector with a thin absorber layer of 0.9 µm, the average integrated QE is improved from 21% to 59%, corresponding to an increasement of 180%.

N-type Ga-free InAs / InAs1-xSbx T2SL strain-balanced on GaSb is conventionally considered as an anisotropic quantum structure with heavy holes highly confined in InAsSb and electrons distributed throughout the structure. It is then somewhat puzzling that Ga-free T2SL detectors have demonstrated optical responses together with modulation transfer function (MTF) at Nyquist frequency quite satisfactorily. To explain these non-intuitive trends, cross-sectional transmission electron microscopy (TEM) investigations have been carried out, highlighting antimony (Sb) segregation across InAs/InAsSb interfaces. As a result, these must be considered as graded rather than sharp, disrupting consequently, the schematic representation of abrupt quantum potentials. In this communication, the experimental Sb profiles coming from TEM images are used to reach a better understanding of important figures of merit such as absorption, MTF and QE.

LYNRED is a leading global provider of high-quality II-VI, III-V and bolometers infrared detectors for the aerospace, defence and commercial markets. Our vision is to preserve and protect, and provide the right technology to customers’ needs. To consolidate our position among infrared detector manufacturer leaders and to enable us to respond to growing market demand for next-generation infrared technologies, a new state of the art industrial facility is breaking ground. This new industrial site named Campus will double the current cleanroom footprint and increase production capacity with optimal cleanliness classification for new high-performance products.

Among these next generations technologies, Campus will serve the ongoing developments of sub-10μm pitch cooled infrared detectors, MCT HOT technology, for extended MW band and III-V HOT MW blue band technology.

We will discuss in this paper the true figures of merit that have to be addressed during technology development and optimization to meet field mission requirements. We will then review latest results on II-VI and III-V HOT IDDCA (Integrated Detector Dewar Cryocooler Assembly) with 7.5μm pitch SXGA format focal plane array in terms of low frequency noise defects, stability and reproducibility of residual fixed pattern noise (RFPN) and Modulation Transfer Function (MTF) optimizations while maintaining high quantum efficiency to keep highest possible range.

In this paper, the first extended SWIR (eSWIR, 1-2.5 μm) focal plane array (FPA) results, based on IRnova’s 2.5 μm cutoff T2SL design are presented. High sensitivity is demonstrated with a signal to noise ratio (SNR) of 215 @ 50% well fill and a dynamic range of 1750 for a full well size of 118 ke- of the CTIA ROIC. Good uniformity across the detectors is evidenced by narrow SNR histograms, uniform response maps and low signal non-uniformity (~1 %). This work is part of the development route towards large footprint (2048 × 512 pixels, 15 μm pitch) HD space prototype eSWIR FPAs, currently performed within the EU-project STEP (Silicon and T2SL EuroPean collaboration for a non-dependent supply chain for large eSWIR FPAs). In addition, a first preview of the HD FPA performance enabled by IRnova’s midwave infrared (MWIR) T2SL small pitch technology is presented, showing an NETD of 32 mK at 120 K with F/3, 60 Hz and 10 ms integration time.

It is well known that avalanche photodiode can enhance the signal to noise ratio of a detection system, when the excess avalanche noise is low. The excess noise factor, F which characterizes the excess noise of an APD can be calculated using the established noise theory from R. McIntyre. When the ratio of hole to electron ionization coefficients, k = 0, F ~2 is achieved at high gain. This means the avalanche gain, M, can be increased without the penalty of increased excess noise factor. In this work, we will present the progress in APDs incorporating InAs and AlGaAsSb as the avalanche regions. Both show k ~0 and therefore F~2. The former can be used for low photon detection at wavelengths beyond InGaAs, while the latter can be combined with InGaAs to provide low noise APD for wavelengths up to 1700 nm. Our work demonstrated that low photons of < 100 photon within a 50 microsecond pulse can be detected using InAs APDs. We also achieved single photon detection at 1550 nm using AlGaAsSb APD.

HgCdTe (MCT) and Type-II Superlattices (T2LS) are the two most promising material systems for high performance, high operating temperature (HOT) infrared imaging applications. This paper discusses the latest developments at Leonardo UK in each material system and provides a performance comparison for HOT MWIR applications. The MCT arrays (640x512/16 μm) were grown on GaAs substrates by Metal Organic Vapor Phase Epitaxy (MOVPE). MOVPE enables precise band engineering of the MCT heterostructure to suppress dark currents while maintaining collection efficiency at high operating temperatures. This approach yields high operability (>99.99%), highly sensitive arrays with an average noise equivalent temperature difference (NETD) of 15 mK at 140 K with F/4 optics. An average high frequency residual spatial noise (HF RSN) of 14.7 mK has been achieved with only 0.1% of pixels showing a gain instability greater than 1.1%. HOT T2SL arrays (640x512/20 μm) on GaSb and GaAs substrates have also been developed in collaboration with Lancaster University. The nBn device architecture was used to suppress Shockley-Read and surface dark currents. The T2SLs on GaSb and GaAs achieved NETDs of 27.4 mK and 28.7 mK respectively when operated at 140 K with F/2 optics. The HF RSN for the T2SL on GaSb was 26.6 mK with only 0.4 % of pixels showing a gain instability greater than 1.1% and an operability of 97.73%. We conclude that both MCT and T2SL arrays demonstrate a clear advancement in HOT MWIR capability at Leonardo UK.

Infrared sensors are an essential technology in the rapid detection and identification of potential threats. Continuous improvements in performance and yield as well as reductions in cost, size, weight, and power consumption are necessary to keep pace with new and emerging threats that are increasing in number and have greater range, speed, and maneuverability. Yield and performance limiting challenges of cooled infrared detector materials and infrared focal plane array processing will be discussed. Paths to addressing some of these challenges including surface passivation, defect identification and analysis, and pixel definition will be presented.

In mid-wavelength infrared detectors built with the InAs/InAsSb superlattice, a study of the absorption behavior near the cutoff wavelength was conducted. Two results are, first, an accurate method for determining the bandgap energy from the spectral response of a fabricated device, and second, an analysis of the Urbach tail of the absorption showing that its characteristic energy is consistent with the dominant phonon of InAs. Additionally, a temperature-dependent measurement of the transport of photo-generated holes in nBn devices can be used to identify the effects of localization due to layer nonuniformities, and to measure the energy step at hole-blocking features.

A variety of mid-, long - and very long– wavelength infrared (MWIR, LWIR and VLWIR) detectors and focal plane arrays utilizing InAs/InAsSb superlattices have been demonstrated in the last decade. At the same time, the transport properties of minority carriers in these structures became an area of active investigation after initial observations of hole localization at low temperatures attributed to the nonuniformity of superlattice layers thickness. In this work we studied the dependence of minority carrier (hole) transport, absorption coefficient and quantum efficiency (QE) of a 5.6 µm cut-off wavelength and of 8.9 µm cut-off wavelength LWIR InAs/InAsSb detectors on temperatures and applied bias. Next, we found the minority carrier (hole) diffusion length and mobility from the measured QE, absorption coefficient and minority carrier lifetime. These results are critical for understanding of the mechanisms of the hole transport in these photodetectors and will help improve device performance.

For over three decades HRL has been known for industry-leading IR detector research and development, and has strived to be agile and adaptable to provide custom solutions for specific mission needs. Over this time HRL has invested heavily in capital equipment and fundamental technology development. This talk will focus on describing our recent research efforts aiming for an overall system/sub-system C-SWaP reduction: curved sensors and small-pitch PFAs for compact optics, wafer scale fabrication for lower sensor cost, small-pitch and high operating temperature sensors for lesser cooler requirements.

The performance of Type II Strained Layer Superlattices (SLSs), incorporating III-V semiconductor materials, in infrared (IR) detectors and focal plane arrays (FPAs) is limited by the presence of surface leakage current. This phenomenon occurs in vertical mesa devices due to surface Fermi-level ‘pin’-ing of the p-type region in detectors built using a pn diode architecture. This is currently mitigated using a unipolar barrier architecture using n-type layers (nBn). Surface passivation of the p-type region in a pn diode via the p-type doping of mesa sidewalls with zinc as the dopant may invert the surface ‘pin’-ing, which may result in reduced leakage current. To properly identify whether this is possible, it must first be proven that the zinc compounds in question can indeed convert n-type SLS to p-type. The simplest way to confirm this is to create simplified homojunction planar diodes using thermal diffusion of zinc into n-type SLS. Thus, this study focused on a new fabrication process for simplified homojunction planar diodes. These planar devices were created using various techniques of zinc deposition and thermal diffusion to create p-type regions within n-type Type II SLS material. Electrical measurements of said devices have been compared to control devices, which consists of an electron blocking barrier to mitigate the surface leakage current. The preliminary results show promising dark current characteristics for several batches of pn diodes. This includes a rectification of 6 orders of magnitude for mid-wave infrared (MWIR) diodes and at least 2 orders of magnitude for long-wave infrared (LWIR) diodes. A detailed analysis of dark current characteristics, along with the spectral response of test devices, will be presented.

ASELSAN has been developing new generation high operating temperature (HOT) infrared detectors to reduce the power consumption of T2SL detectors. In this paper, recent results for HOT T2SL detectors for mid-wavelength infrared (MWIR) technology at ASELSAN are presented. Performance is shown for 640x512 format 15 µm pitch IDDCA with average noise equivalent temperature (NETD) and pixel operability values of <25 mK (F/4) and >99.5% at 110 K, respectively. These NETD and operability values remain unaffected by temperature between 77 K and 110 K.

Graphene-based infrared photodetectors are promising devices that exploit the unique optoelectronic properties of graphene, including its broadband light absorption characteristics, rapid response, and high chemical stability. However, graphene exhibits a low absorbance (2.3%), which limits its photoresponsivity. This paper introduces sensitivity-enhanced InAs/GaInSb type-II superlattice (T2SL) infrared photodetectors fabricated using a graphene diode structure. The devices consist of graphene diodes and InAs/GaInSb SLs grown via chemical vapor deposition. The T2SL structure is employed for both photocarrier supply source and carrier density modulation of the graphene diodes to improve the sensitivity of the devices. The dark current in the graphene diode device is reduced to less than 1%, which is lower than that in the GFET device, and the responsivity of the devices is significantly enhanced using the photogating effect. These highly sensitive and low-dark-current devices are expected to promote the development of high-performance graphene-based image sensors.

Currently, one of the Defense Advanced Research Projects Agency (DARPA) Microsystems Technology Office (MTO)’s largest initiatives is the Electronics Resurgence Initiative (ERI 2.0), the drive to advance 3-Dimensional Heterogeneous Integration (3DHI). Infrared focal plane arrays were the original 3DHI device, but lessons can be learned from this new initiative. The talk will center on advancement in new materials, advancements in manufacturing capability and leveraging advanced compute technologies. The talk will include ongoing efforts in infrared and thoughts for the future.

For several years, LETI and Lynred (within DEFIR common laboratory) has been working on a new version of its P/N structure. This new generation (NG) process flow is a complete overhaul of the MCT P/N fabrication, focusing on lowering process induced defects in the narrow gap absorbing material. It is therefore specifically designed to optimise second order figures of merit such as stability, BSFR, RTS pixels. Until now, this technology has been intensively focused on MWIR band for high operating operation [ ][ ][ ], with 7.5µm pixel pitches, for tactical applications. This work results in very interesting performance FPA demonstrations for the next generation of MCT MWr detectors at 130K and even at 150K. We now investigate the possibility to adapt this NG flow to longer wavelength such as LW (9.3µm@80K). First arrays exhibit almost no distribution tails, and measured dark currents remain very low down to very low temperatures (below 100e/s at 40K). This paper also intend to discuss the potentiality of this NG structure for the VLWIR (15µm@65K) band intended to address future space applications for earth observations.

For several years, CEA-LETI has worked on the development of IR MCT detectors for low flux applications in scientific imaging. MCT has remarkable material properties that allow for highly performing detection, with high QEs and minimal dark currents. Currently, both Teledyne US and LETI-Lynred in France achieve dark currents in the range of a fraction of e/s/pixel for NIR imaging, utilizing the p-on-n extrinsic diode structure, for astronomy applications. As part of the NEOCAM project, Teledyne has demonstrated the ability to extend the cut-off wavelength to significantly longer wavelengths (10.3μm and recently 13μm) while keeping the dark current in the e/s range. Furthermore, LETI is presently enhancing its p-on-n technology to satisfy the demanding specifications of low-flux applications. Achieving very low dark current leakage and large diode polarisation plateaus is required to achieve SFD input stage ROIC operation and to reach such low dark current values. This entails the mitigation of tunnelling currents that appear in low-gap materials. In this report, we present the production of a 15μm pitch TV-size prototype array that operates in the LW range (8μm @ 35K). Dark current values as low as 0.5 e/s/pixel have been measured below 40K, and will be discussed.

In this study, we fabricated bolometer-type uncooled infrared focal plane allays (IRFPAs) of 640 × 480 pixels with high-purity semi-conducting single-walled carbon nanotubes (SWCNTs) as detection materials for the first time. The thermal isolation structure of the IRFPAs for high responsivity was realized by creating a cavity between the contact electrode and the infrared detection part and by connecting them with beam wiring. The infrared detection part was formed in the order of SiN_x film, semiconducting SWCNT network film, SiO₂ film, and SiN_x film from the bottom. Especially the SWCNT network film was only formed by a printing process except for the fabrication process in micro electro mechanical systems (MEMS). Here, our semi-conducting SWCNTs, which is a dispersion containing a nonionic surfactant, formed a high-density film with locally-oriented structure by the coating process. The responsivity and thermal time constant of typical element in long-wave IR region showed over 10⁵ (V/W) @0.2 V and 5 ms, respectively. Assuming the thermal conductance and infrared absorption rate, temperature coefficient of resistance (TCR) was estimated as above -5%/K. The TCR value was similar with that of semi-conducting SWCNT network film prepared on Si substrate and about three times larger than that of conventional vanadium oxide film. Therefore, we found that semi-conducting SWCNTs become a promising bolometer material that can achieve high sensitivity.

Road fatalities that represent 1.3 million death each year is the 8th cause of decease in the world, 54% of them are Vulnerable Road Users. In the United States or Europe, 75% of fatalities happen in poor visibility conditions.

Active safety is a promising way to reduce road fatalities with features like Automatic Emergency Braking (AEB). Currently, it relies mainly on RGB camera and radar that suffer from limitations in challenging situations that represents the majority of accident situations. These challenging situations include nighttime, headlamp or sun glare, rain and fog. NHTSA latest rulemaking proposition requires AEB systems that work during day and nighttime conditions for pedestrian and car detection. Thermal imaging is a complementary technology to visible cameras and radars to extend AEB use cases to these challenging situations.

After defining the requested Recognition range for pedestrians related to NHTSA rulemaking proposition requirements, the paper will explore thermal imaging capabilities for pedestrian detection in daytime and nighttime conditions compared to a commercial vehicule visible system. Impact of pixel pitch on pedestrian Recognition range performance is presented. Finally, a $100 thermal camera configuration that covers the NHTSA rulemaking proposition requirements is described.

As uncooled microbolometer market grows, there is a need for cost-reduced detectors with the right performance level for the considered market. CMOS devices as transistors or diodes are therefore promising alternatives to standard thermistor materials of microbolometers. In this context CEA LETI developed a 12μm pitch proof of concept of a FDSOI transistor-based microbolometer suspended pixel. The suspended pixel is realized with a 3D integration technological process. This proof of concept aims to validate the technological process by demonstrating pixel capacity to be sensitive to the infrared ux. This work reports details on technological process, electro-optical measurements and discussion on achievable performances.

Small Pixel High Definition (SPHD) IR Cameras continue to improve in performance, resolution, and yield. SPHD product adoption is helping drive important performance goals such as sensitivity, resolution and other features. We report on continued developments of high-resolution small pitch infrared camera system technology developed at Cyan Systems. We highlight demonstrated imaging capability from two recent, large format, infrared focal plane array architectures. Specifically, we present results from our full-high-definition (FHD) 5-micron pixel CS-3 camera now capable of broadband (~0.7 – 5.0 micron) wavelength sensitivity. We show more results from our newest digital readout integrated circuit (DROIC) small pixel mid-wave infrared camera with ultra-high-definition (3840 x 2160) format, and Cyans CS-3 full-high-definition (1920 x 1080) Broadband IR camera.

In modern, wide distribution, defense and commercial applications, such as hand-held cameras and small payload systems, a High Definition (HD) Mid-wave Infrared (MWIR) detector is desired. This is to provide both a wide Field of View (FOV) and / or an extended range of Detection, Recognition and Identification (DRI). At the same time, many of these applications also require a solution that is of low Size Weight and Power (SWaP) and with a high degree of reliability.

Typically, the requirements for a large, cooled HD array conflict with those for low-SWaP and high reliability. To overcome this challenge, SCD developed a new state-of-the-art detector that is based on the Sparrow-HD Focal Plane Array (FPA). The Sparrow-HD MWIR FPA has a 5μm pixel and 1280x1024 format. The FPA includes an advanced Readout Integrated Circuit (ROIC) that has several operation modes, such as standard video output at low power consumption, high frame rate output (detection mode), multiple types of binning modes, a high sensitivity mode and more. All operation modes can be controlled via communication from the host system. The Sparrow HD ROIC is bonded to a High Operating Temperature (HOT) XBn-InAsSb IR-sensing material that operates at 150K. This material is sensitive to the 'blue' part of the MWIR spectrum where the atmosphere is most transparent and represents a mature SCD technology. The ability to operate at 150K greatly supports both the low SWaP requirement and the requirement for extended cooler reliability.

One of the development challenges of a 5um pitch FPA is the ability to maintain high electrooptical performance for such a small pixel. It is shown in this article that the Sparrow-HD FPA maintains a level of electro-optical performance that is similar to SCD's 10μm pitch Sparrow 640×512 FPA, including high quantum efficiency, low dark current, low cross talk, high array uniformity, and high operability.

At the detector module level, the small size and low power FPA enables the use of a highly reliable compact dual-piston split-linear cryogenic cooler, and low-power proximity electronics. Hence, the Sparrow HD module is one of the lowest SWaP sensors available in the industry today. The key characteristics and performance of this new module are detailed herein including its compatibility with a large variety of IR applications.

Overall, the Sparrow-HD module brings HD resolution to all compact tactical systems that previously were limited to VGA solutions in terms of detector SWaP, Cost and Performance.

In 2022, Leonardo UK presented the first results from Condor HD, a 12μm MWIR-LWIR Dual Waveband Infra-Red (DWIR) high-performance infrared detector, grown by Metal Organic Vapour Phase Epitaxy (MOVPE) on GaAs substrates. By using a “back-to-back” diode structure, these pixels are spatially coherent, and changing the bias polarity across the stacked diodes provides sensitivity in the desired waveband (in this configuration MWIR or LWIR).

This paper discusses further characterisation and development of the CMT structure, demonstrating improvement to spectral bandwidth, QE and MW defects. Leonardo UK have also performed further dark current measurements and spectral crosstalk measurements on these new wafer designs.

Direct MTF characterisation (in both the MWIR and LWIR bands) has enabled confirmation that optical crosstalk between neighbouring pixels in-band is equivalent to that seen on single band MWIR and LWIR devices - results of which are reported herein. Retaining the DWB mesa structure also seen on the 24μm Condor II Detector has been key to this.

Lynred is leading the development of infrared detectors for high performances applications. Two trends are identified in the infrared range, the increase of the operating temperature and the pixel pitch reduction. For 15 years, the III-V technologies present an increasing interest to address both challenges. At LYNRED, these technologies allow to address Short Wave InfraRed (SWIR) and Mid-Wave InfraRed (MWIR) for ground applications. Many challenges have to be addressed for the future focal plane arrays (FPAs). Electrical and optical crosstalks as well as image quality and stability, are one of the prime concern for detectors with pixel pitch down to 7.5μm. In order to reach an industrial production level of infrared FPAs, technological developments are required at each steps: the epitaxy, the detector array process, flip chip and back end processing. Another key element is the Read Out Integrated Circuit (ROIC) designed in-house to fulfil our customer needs.

We review the latest developments at LYNRED on III-V technologies, in terms of operability, residual fixed pattern noise (RFPN) and Modulation Transfer Function (MTF) optimizations.

Thanks to their high technology readiness level, quantum well infrared photodetectors (QWIP) provide an efficient and swift solution for meeting the increased demand for advanced LWIR imaging systems. IRnova’s present portfolio includes QWIP detectors for LWIR dual-colour, gas detection, and polarimetric imaging on 30 and 15 μm pitch, while the development of large-format HD arrays on 10 μm pitch is ongoing.

In this work, the latest advancements for LWIR QWIP detectors (peak absorption at 8.5 μm) are presented: firstly, focusing on the progress on HD-format detectors on 10 μm pitch and secondly, presenting the enhanced polarization contrast in IRnova’s VGA-format polarimetric detector Fenrir (640×512 on 15 μm pitch). In the new Fenrir, the polarization contrast has increased from ~25% to ~40%, resulting in improved tracing of the polarimetric signatures as visualized by field tests. Furthermore, by employing array-wide pixel-level spectroscopy, excellent spatial uniformity across detector arrays has been confirmed.

This conference presentation was prepared for SPIE Defense + Commercial Sensing, 2024.

CI has developed a modular optical system, which provides the sensor stimulus to obtain the required quantitative spectral response of single detectors, detector array engines and camera systems with small to large aperture optics. The system includes interchangeable sources, Circular Variable Filter scanning monochromator (CVF) and collimating and focusing optics to project monochromatic radiation (in focused or collimated configuration, according to need) towards the sensor. When spatial patterns are also used on the focal plane, the Unit Under Test (UUT) is fully characterized in both spectral and spatial domains. The systems’ description and some examples of detector and camera measurements have been published in SPIE Vol. 12737, 127370O-1, 2023, but here we add a measurement of MTF versus spatial frequency at different wavelengths of a commercial infrared camera in the range of 3 to 5 microns.

The polarimetric thermal imaging framework offers comprehensive capabilities that can significantly enhance operations within the Defense and Security sectors. The combination of polarimetry and thermal imaging brings several advantages that can dramatically impact various aspects of the security and defense sectors. Polarimetry provides a new set of capabilities due to the nature of the data received from the sensors, coupled with the ability to process such received data. We all know the thermal world when temperature and emissivity are processed to a temperature map and converted to a thermal image. This, though, has its limitations in many applications when the underlined reliance on temperature is challenged when the addressed object is represented in a small number of pixels and or its background is “noisy” or represents a cluttery scene. The polarimetric thermal imaging framework offers comprehensive capabilities that can significantly enhance operations within the Defense and Security sectors. The combination of polarimetry and thermal imaging brings several advantages that can dramatically impact various aspects of the security and defense sectors.

Computer vision systems, such as object detection, traditionally rely on supervised learning and predetermined categories, an approach facing limitations when applied to infrared images due to dataset constraints. Emerging contrastive vision-language models, like (Contrastive Language-Image Pre-Training) CLIP, offer a transformative approach through their pre-training on extensive image-text pairs, providing diverse visual representations integrated with language semantics.

Our work proposes a novel zero-shot object detection approach for infrared images by extending the benefits of CLIP into this domain. We have developed a two-stage detection system using CLIP for detecting humans in infrared images. The first stage involves region proposal by a (You Only Look Once) YOLO object detector, followed by CLIP in the second stage. When compared with a YOLO model fine-tuned using infrared images, our proposed system demonstrates comparable performance, illustrating its efficacy as a zero-shot object detection approach. This method opens up new avenues for infrared image processing leveraging the capabilities of foundation models.

The rapid advances in deep learning AI techniques for digital vision-based perception and gains in computational imaging for image quality have converged with innovations in mobile processors and device support to bring very large computing power to the edge. This convergence is creating opportunities for electro-optical systems to become intelligent at the edge and to eliminate issues with latency, compression artifacts, datalink bandwidth, thermal management, and system complexity. We describe the state of the art in embedded processors and the integration of Teledyne FLIR’s Prism^TM thermal and multispectral image signal processing and object detector and tracking libraries into today’s most widely deployed embedded platforms.

The ability to accurately ascertain an observer’s position directly from imaged scenery is an important technological capacity, especially given the susceptibility of global positioning system (GPS) signals to interference. Horizon matching has been demonstrated as a method of geolocation in regions with sufficiently rich topography, such as in mountainous terrain. In this method, digital elevation data is processed to yield simulated imagery of horizon features, and this is then matched to real scenery images to back-calculate the imager position. The effectiveness of this method depends on several attributes of the imaging system, including its resolution, range performance, contrast-to-noise ratio, and others. As such, cameras operating in different spectral bands – visible, near-infrared, mid-wave infrared, and longwave infrared – offer distinct advantages and drawbacks for this task.

Here, we demonstrate geopositioning via horizon matching with a vehicle-integrated, gimbal mounted multi-band imaging platform that facilitates this functionality with visible, NIR, SWIR, MWIR and LWIR imagers. Using FOV-matched cameras, performance of the method was evaluated for single images and for panoramic imagery. We present a statistical method of evaluating this and similar approaches by executing Monte Carlo simulations. We then exploit this approach to find multiple solutions and down select these based on an error/fit metric. By exploiting the fit metric, we demonstrate accuracies for each band of 100m or better, which compares well with comparable geolocation approaches. We compare performance of the different bands and generally assert that the accuracy of each band depends on how well the fit metric and position error correlate for that band.

Bulk grown wafers had been used for fabricating photoconductive (PC) HgCdTe detectors for several decades until recent years. As bulk wafers are getting gradually depleted over years, epitaxial grown HgCdTe wafers are becoming the only choices available. This paper reports the very long wavelength Infrared (VLWIR) PC HgCdTe detector development (cutoff wavelength ~ 17μm at LN2) at Teledyne, leveraging the state-of-the-art molecular beam epitaxy (MBE) material technology on CdZnTe substrates. These MBE wafers provide much larger wafer sizes, better uniformity, and in general better detector performance than conventional bulk wafers. Detailed detector performance comparison was performed between MBE and bulk wafers on detectivity (D*), responsivity, spectral response, etc. for 1mm and 0.25mm discrete detectors. The VLWIR MBE PC HgCdTe detectors are now in volume production at Teledyne.

InAs is a very attractive material for high performance transistors, optical applications, and chemical sensing. However, it has been very challenging to achieve high stability surface passivation layer over InAs due to the very high leaky InAs and passivation interface. Various passivation method attempts in the past were not successful at TJT as they all caused significant degradation of InAs detector performance. As a result, no surface passivation has been used for TJT standard InAs photodetectors until now.

In this paper, we report for the first time a successful development of a new surface passivation process that is suitable for TJT InAs mesa photodetectors. This passivation did not cause InAs detector performance degradation and showed good stability and process compatibility with the detector assembly/packaging processes. Etching methods have been evaluated and applied to form InAs MESA photodiodes. Afterwards, multiple paths for surface treatment and passivation, including wet treatment, Polymer Encapsulation, Atomic Layer Deposition and Thermal Evaporation, have been compared and applied to the as developed photodiodes. Extensive characterization on InAs MESA and passivation quality were then performed. Key control factors, including surface treatment, MESA height, junction depth, etc., have been studied and optimized through design of experiment (DOE). Optical and electrical characterizations of detector performance have been performed and analyzed, including dark current, capacitance, shunt resistance, spectral responsivity and QE, and spatial uniformity over various temperatures. By optimization of passivation process, the significantly improved device performance stability has been achieved and presented in this paper. In addition, the new surface passivation layer also serves as an anti-reflection coating (ARC) that enhances the InAs detector spectral response and QE when optimized to the wavelength of interest.

There has been a tremendous amount of research on two dimensional materials (2DMs) in recent years, suggesting their unique properties for optoelectronic devices. While a good momentum on implementing 2DMs for photodetection for visible and infrared (IR) photon detection exists, progress on demonstration of imaging systems based on these material have been slow. Most of reported studies have been based on single-pixel devices, which is unable to compete with the quantity and quality of information provided by massively parallelized mega-pixel imagers based on complementary metal-oxide semiconductor (CMOS) readout electronics. In this paper, we explore opportunities for achieving reliable and high-resolution FPA cameras using 2DMs. We will cover most relevant new materials in the field and cover photodetection methods. Our goal is to address the opportunities and challenges of using 2DMs for future imaging systems and their integration with CMOS electronics in a condensed form.

A 65nm node RF and Analog CMOS process is described with advanced features for use in next generation ROICs. This process is in a unique position to enable both digital pixel ROICs and conventional ROIC architectures. The production process exists in a high-volume commercial fabrication facility and is being offered to aerospace and defense customers. Features to enable large array formats, such as stitching, up to nine layers of metal, low voltage operation are included, as well as multiple analog FETs, in particular low leakage, spanning low voltage up to 5V. Several analog features such resistors and MIM capacitors, and reconfigurable elements such as memory, e-fuse, will also be described. The platform process and device features, and special PDK features such as cryogenic models, will be related to select circuit block functions and requirements for large format applications such as cooled and uncooled ROICs.

Indium gallium arsenide and colloidal quantum dot SWIR sensors can produce stronger contrast imagery than their visible counterparts due to the reduced scattering in the SWIR band. A 640 x 512 format, 10 μm pixel pitch low-noise highsensitivity DROIC, with a capacitive transimpedance amplifier pixel front end, for SWIR imaging is presented. This DROIC has variable gain pixels with well capacities of approximately 22 ke- in high gain, 160 ke- in mid gain and 1.1 Me- in low gain. The readout boasts a low read noise of only 15 e- rms at room temperature in high gain with correlated double sampling. This DROIC can run at 700 fps full frame and 8.9 kfps for 32 x 32 window.

In conventional IRST systems, hot targets are periodically searched in a wide field of view cold background and any threats identified are then tracked using very narrow field of view windows. This sequential and discontinuous search-now track-later, track-now search-later operation is effective only for relatively fixed background scenes with very few threats. In the proposed ROIC pixel array for advanced IRST, individual pixels communicate potential threats locally in a swarm intelligent manner to accomplish simultaneous and continuous search and track globally across the entire field of view. This search-now track-now operation of the swarm intelligent ROIC pixel array for advanced IRST is demonstrated using simulations and processed imagery.

The paper presents two approaches to reduce vibrations in miniature integral Stirling cryocoolers. Approaches were applied to cryocoolers developed and produced by LE-TEHNIKA. First, research done on a linear cryocooler is presented where vibrations were reduced with a passive damper, comprising of a vibrating mass and a spring. Importance of damper eigenfrequency and mass with regard to damper efficiency is discussed. Next, research done on a rotary cryocooler is presented where vibrations were reduced by using two balancing masses on a shaft. Vibrations were measured at different speeds. Measurements are presented as absolute values and in spectral domain, in both cases clear improvements can be seen.

The paper presents two approaches to address the possibility of cooling IR detectors with JT coolers which work at temperatures higher than 100K. Considering how to achieve required temperature, the first part of research focuses on finding the proper working gas (or mixture) with liquefaction point in the required temperature range. Results of findings will be presented with focus on gas flow and regulating gas tuning to achieve short cool down times and proper temperature stability. Part of the focus will be on cool down time comparison of such systems toward a classical JT using argon or air in DDA with similar thermal mass. Benefits and drawbacks observed when using such approach will be compared.

The second approach to be presented is the use of unique Actively Controlled JT cooler (ACC) which is capable to work at different IR detector cryostating temperatures above 100K. In addition, challenges which are associated with such approach are presented. Le-tehnika has quite some experience using the ACC at 100K level while levels above 100K still bring significant research challenges regarding the temperature stability on the detector. The paper will describe how we approached these challenges, and cooling results achieved at different temperature levels will be presented. Finally, achieved technology level will be evaluated and some possible improvements will be proposed.

Rotary Stirling cooler reliability was considered as a limitation compared to linear Stirling coolers. Nevertheless, cooler reliability is a major performance requested by customers, especially for 24/7 applications, which are a growing market. Indeed, most of the time, coolers are one of the components dimensioning the lifetime of the system. This is due to the fact that the cooler remains a mechanical system with moving parts.

On the other hand, rotary Stirling coolers are a very good solution to reduce SWaP (Size, Weight and Power) at system level as they are more compact and efficient. Thus, several improvements have been made on rotary coolers in order to fill-in the reliability gap between linear and rotary coolers. Reliability improvement is an important part of Thales rotary coolers’ roadmap in order to propose on the market coolers able to answer to SWaP and reliable applications. For instance, Thales claims that the RM2 reliability is higher than 50,000h for a typical mission profile.

Increasing the cooler reliability becomes a challenge when the times come to validate evolutions. Indeed, lifetime tests are necessary before releasing an evolution but it is necessary to wait the end of the tests. For instance, with a reliability higher than 25,000h, several years are needed before the results. This is an important aspect that can explain the difficulty to increase the reliability.

The paper will focus on the latest works made at Thales on rotary coolers in the frame of that target. Works on Thales coolers will be used as an example. Firstly, we will illustrate the latest reliability improvements made on this cooler. In a second part, we will describe how to accelerate lifetime tests. Finally, the lifetime tests results will be presented.

In an initial work in 2018 we presented the conceptual idea to use a so called shock-pulse detection sensors board for detecting in advance upcoming damage inside the mechanics of widespread used rotary Stirling coolers in infrared detectors with the intention to implement a preventive maintenance scenario, based on significantly better End Of Lifetime (EOL) prediction as compared to pure MTTF statistics based on lifetime analysis.

In the meantime, we developed an own Integrated Sensors Board (ISB) in combination with commercially available ultrasound (>20kHz) sensitive MEMS sensors, supposed to be used in deployed cooled IR imager platforms, especially used for 24/7 continuous surveillance applications. We report on the specific electronic signal and data processing design and layout of our sensors board solution, where an effective data reduction and further analysis is applied down to calculation of relevant lifetime and state of wear figures for the definition of an effective lifetime model of the cooler mechanics, especially the bearings used on the coolers compressor.

As part of RICOR’s goals to add the ability of failure prediction to its coolers, for improving customer’s Life Cycle Cost (LCC) , tests were performed with the ISB. First test results based on accelerated endurance lifetime tests performed at RICOR test facility on rotary Stirling coolers are reported and show a clear and robust indication of relevant state of wear figures, that can be used as end lifetime parameters, enabling effective alert to perform preventive maintenance.

We clearly differentiate the herein reported methodology from frequently reported attempts based on vibrational analysis in the acoustic regime, where a strong dependence on the structural built-in conditions and the surrounding mechanics can make the clear indication of increasing wear induced damage inside the cooler mechanics, especially the bearings, almost impossible.

Cryocoolers are needed in modern high-performance infrared cameras to establish and maintain the cryogenic temperature of infrared focal plane arrays. Attollo has a number of cryocooler development efforts ranging from low SWaP linear microcoolers for HOT MWIR sensors to high lift, high reliability coolers for 80K operation. In the case of cryocoolers designed for HOT MWIR applications, Attollo is also developing low-cost designs to address the attritable platform market. Attollo will present an overview of these design programs and data on the performance of initial units.

Increasing interest in flying infrared sensor payloads on small satellites is driving the need for small scale, low input power (say, < 40W) cryocooler systems. Numerous tactical Stirling cryocooler models are available in this power range from a number of established manufacturers. In addition, Lockheed Martin has developed a miniature pulse tube cryocooler well-suited to meet the aggressive performance and packaging requirements for a small satellite infrared payload. Up until now, the space industry has lacked suitably matched small, radiation tolerant cryocooler control electronics to drive such cryocoolers. West Coast Solutions, in collaboration with Creare, has recently completed the design, build, test, and environmental qualification of a new product dubbed the Compact Cryocooler Control Electronics (C3E), which has been architected from the bottom up with a focus of minimizing packaging volume. The result is a new generation of small satellite cryocooler electronics weighing less than 400 grams. In addition to the environmental qualification testing, integrated thermal vacuum testing was performed with the C3E and the Micro1-2 Lockheed Martin Microcryocooler. A design overview of C3E, performance and qualification testing of the C3E, and the results from the integrated C3E - Microcryocooler test are presented.

The vibration resulting from an imbalanced motion of piston and displacer assemblies within Stirling linear cryocoolers poses significant challenges in the context of long-range, high-resolution, and low Size, Weight, and Power (SWaP) handheld and gyro-stabilized infrared imagers.

Addressing this challenge, CryoTech has introduced an innovative and cost-effective micro-miniature split Stirling cryocooler featuring a single-piston compressor and a pneumatic expander, the vibration export of which has been effectively reduced at the source by substantially decreasing the weight of the moving assemblies. For vibration-sensitive applications, the authors provide an optional Tuned Dynamic Counterbalancer featuring a linear failure-free magnetic spring. This patent-pending solution enables not only a failure-free operation of a substantially lighter device but also leads to a substantial reduction in the damping ratio, thereby additionally enhancing the vibration attenuation ratio at the driving frequency.

The authors provide a comprehensive overview of the outcomes derived from a thorough feasibility study, encompassing both theoretical analysis and full-scale experimentation.

In a companion paper in this session, the performance characteristics and Flight Qualification environmental test result for the Compact Cryocooler Control Electronics (C3E) are described. This paper describes a variant of the C3E, one optimized for slightly higher power applications and/or applications requiring additional mission assurance features. While applicable to essentially any Stirling or pulse tube cryocooler in the 50W and lower power class, this version of the C3E is being developed for and in collaboration with Northrop Grumman to provide flight electronics for the MicroCooler Pulse Tube Cryocooler (MicroCooler). This version has therefore been dubbed the “C3E-PT.” The C3E-PT extends on the success of the C3E by increasing the power handling capability to above 50 WAC for bus voltages as low as 22 VDC to take better advantage of the available cooling power from the MicroCooler. In addition, features have been added to protect the cryocooler in the event of a C3E-PT or bus transient, say due to a single event upset (SEU). New capabilities include provision for a knock sensor and clock synchronization between multiple C3E-PTs. Details of these new features and progress in the development effort are discussed.

Thales Cryogenics presents a new product in its portfolio which leverages the reliability of the pulse-tube cooler, which has shown to be better than 99% reliability after 10 years of operation. This new product development was aimed specifically at IDDCA applications. Design choices and test results will be presented.

Due to its relatively short history, high operating temperature (HOT) cooled IDDCA’s MTTF value testing results are difficult to obtain and hard to predict or estimate. However, many cryocooler manufacturers in the market already have and can provide cyrocooler’s MTTF testing data at 77K or 80K operating temperatures. We conducted tests of IDDCA at various high operating temperature settings and measured coolers running speeds. We then applied calculation methods to calculate and predict its MTTF based on 77K test results and measured cooler rotational speeds at different operating temperatures and cooler settings. We conduct integration of cryocoolers with detectors and dewars and have found such predictions can be used as good reference for cooler MTTF predictions at a particular high operating temperature.

Since more than 15 years, AIM is developing and fabricating dual opposed piston linear coolers with moving magnet motors. Key advantage of such coolers are high MTTF and thus low total cost of ownership, low exported vibration and modular and geometrical flexibility.
SX035 compressor and 6mm standard coldfinger are in serial production for several production programs.
AIM will report on recent product improvements with regard to harsh environments (high ambient temperatures, random vibrations and constant accelerations) and performance enhancements. These changes include compressor, regenerator and cooler drive electronics.

Although black phosphorous (BP) is a promising two-dimensional material for next-generation infrared (IR) photodetectors, enhancing its quantum efficiency remains challenging. Herein, we proposed a hybrid BP–plasmonic nanograting with high aspect ratios for use in advanced functional IR photodetectors. Plasmonic nanogratings with high aspect ratios exhibit wide-angle near-unity absorption in the IR-wavelength region; this absorption is based on the grating depth. By forming BP on top of the plasmonic nanogratings and modifying the edge structure of BP, we achieved a hybrid structure that exhibits strong absorption. The results demonstrate the viability of BP-based high-performance IR photodetectors.

In our recent investigation, we discovered Si-metal Schottky junction being able to detect mid-infrared spectrum under certain conditions. This work investigates the influence of the hot-carrier diffusion distance on such photodetectors to enhance responsivity in the mid-infrared (MIR) range. Due to the rapid decay characteristics, hot carriers disappear very fast. Thus we control the diffusion distance of hot carriers by varying the thickness of the metal thin film. A proper thickness of the metal boosts the responsivity for nearly 30-fold enhancement. Additionally, a mathematical model is employed to validate experimental results of hot carrier diffusing toward and leaping over the barrier. Furthermore, this research implements back-side illumination, bringing the excited carriers closer to the metal/semiconductor interface. The shortened diffusion distance of hot carriers leads to an increased responsivity in the photodetector within the MIR range. Consequently, it enables the detection of infrared (IR) signals with wavelengths of up to 4.26μm.

Lenses for use in the infrared (IR) wavelength region are key elements of IR image sensors, and determine the cost and performance of such sensors. As an alternative to a conventional lens, we designed and fabricated a silicon-based metalens in order to realize a compact, high-performance IR focal plane array (IRFPA) system. The metalens was developed using an automatic inverse design technique based on a rigorous coupled wavelength analysis. It consisted of a periodic array of pillars fabricated by deep reactive-ion etching of a silicon wafer. This metalens was designed for the 80×60 IRFPA used in the Mitsubishi Electric Corporation MIR8060B1, which comprises an array of pn-junction diodes formed on a silicon-on-insulator layer. It is expected that this metalens-based IR sensor will expand the range of applications of such sensors.

We fabricated extended SWIR photodetectors with cutoff wavelength of 2.3 μm by using lattice-matched InGaAs/GaAsSb type-II quantum wells as an absorption layer. The 100-pair InGaAs/GaAsSb quantum wells and InGaAs as a cap layer were grown on an n-type InP substrate by molecular-beam epitaxy. The p-n junction was formed by selective zinc diffusion using rapid thermal annealing. For dark current reduction, photodetector with a barrier layer between the absorbing layer and the cap layer was also fabricated. In each device, in addition to absorption in the InGaAs cap layer, absorption which is possibly originating from the quantum well layer was observed in a wavelength range from 1.6 μm to 2.3 μm. By comparing dark current of each device, dark current reduction by the barrier layer was also confirmed.

Graphene/semiconductor heterojunction photodiodes that use photogating are expected to perform better than conventional infrared (IR) photodetectors. However, interface instability limits has prevented the realization of the theoretically predicted performance and high reliability for these devices. This study focuses on optimizing the material and thickness of an interfacial layer in a graphene/InSb heterojunction to achieve a high-performance mid-IR photodetector. The results indicate that HfO2 is a more suitable material than Al2O3 for the interfacial layer, and 1-2 nm is the thickness that best promotes effective photocurrent transport. This interfacial layer can facilitate the fabrication of superior IR image sensors based on graphene/InSb heterojunctions.

Previous research in infrared sensing mainly focused on narrow bandgap semiconductor materials, tunable bandgap two-dimensional (2D) materials. However, it is challenging to integrate them with silicon electronics due to lattice mismatch with silicon. To address this challenge, this work proposes a concept of infrared detection different from that of narrow bandgap semiconductors and 2D materials. In this study, thin metal/semiconductor Schottky devices were fabricated to realize mid-infrared light detection by collecting thermal signals generated by hot carriers with energy lower than the Schottky barrier. Experimental results demonstrate successful detection of mid-infrared light signals at wavelengths of 3.22 μm, 4.28 μm, and 4.83 μm, surpassing the cutoff wavelength corresponding to Schottky barrier. Such Schottky devices exhibit a maximum responsivity of 0.680 mA/W, which confirms their efficiency and application potential in application of mid-infrared optical detection.

T2SL (Type II Super Lattice) has become one of the most important material for infrared detector. It has now widely used for HOT MWIR detector and large format LWIR detector. The HOT detector is especially important for satellite application because HOT detector occupies small volume and requires small power. In this work, the radiation test results of MWIR T2SL nbn detector will be presented. The developed hybrid chip has the format of 2048 x 2048 pixels with 10 μm pitch. It was fabricated with Ga-free InAs/InAsSb absorber layer and GaAsSb barrier layer. The quantum efficiency of the developed hybrid chip is larger than 50% and the dark current is below 2 x 10^-8 A/cm². To be used in the space environment condition, the TID (Total Ionizing Dose) effects and DD (Displace Damage) effects were tested and test results are presented.

The incorporation of graphene, known for its outstanding electrical, mechanical, and thermal characteristics, with infrared (IR) technology, has emerged as a promising research domain with potential applications spanning environmental monitoring, healthcare diagnostics, and security enhancements. Through a bibliometric analysis of a vast array of recent publications, this study examines the growth, trends, and pivotal contributors in the field of graphene-IR research. Our findings demonstrate a significant increase in research activities, highlighting the field's growing importance in the development of sensors, modulators, and detectors leveraging graphene. This research is identified as inherently interdisciplinary, merging insights from materials science, photonics, and nanotechnology. A notable transition is observed from theoretical research towards practical applications, with an emphasis on the healthcare and defense industries, reflecting a broader interest in graphene-IR devices' performance enhancement. The analysis also points to an expanding research landscape that includes the exploration of other two-dimensional materials and the innovation of new device structures. This paper not only outlines the current advancements and challenges in graphene-IR technology but also anticipates its capability to drive forward IR applications through enhanced device performance and innovative approaches. Offering a comprehensive review of the trajectory and potential within this field, the analysis provides valuable insights for researchers navigating the complexities of materials science combined with IR technology, indicating a vibrant growth trajectory and promising future for groundbreaking developments.