Methane is a greenhouse gas that has a global warming potential (GWP) of 25 relative to carbon dioxide (CO2). In 2021 an estimated 36 billion-tons of CO2 and 640 million-tons (16 billion-tons GWP equivalent) of methane were emitted. Emission consists of anthropogenic and naturally occurring sources with natural emissions accounting for 35-50% of total emissions. Natural emission caused by decaying organic matter in wetlands and melting tundra, increase as global temperatures rise, thus creating a positive feedback loop increasing their significance and exacerbating global warming. Effective mapping of natural emissions requires high field-of-view (FOV) global satellite coverage. Detection of small weak sources and mapping of larger plume nonuniformity requires a small ground-sample-distance (GSD). Methane has several fine spectral features in the SWIR allowing for effective detection and quantification. Methane concentrations can be retrieved by finding the atmosphere that provides the smoothest retrieved ground reflectance, thus fully removing the absorption features of the gas. The retrieval technique uses the uniform background assumption, which assumes that scattered radiance from pixels adjacent to the pixel of interest (POI) share the same material. While scattering is diminished in the short-wave-infrared (SWIR), methane retrieval accuracy will still be affected when there is significant background and POI contrast and the distance of adjacent scattered radiance entering the POI far exceeds the pixel GSD. In this paper we study the effects of the scattered adjacent radiance on retrieval, based on GSD, background and POI reflectance contrast, and the amount of scattering with varying aerosol loading.

Thermal conductance is a controlling parameter for heat transfer in microbolometer based infrared imaging systems. The thermal conductance can be measured by monitoring the microbolometer temperature change induced by a known electrical power excitation due to constant voltage or current Joule heating at thermal equilibrium. The temperature change is calculated from the corresponding resistance change by using the conduction mechanism for the microbolometer thermosensitive material. For amorphous semiconductor materials, such as VOx and amorphous silicon, electrical conduction is by Variable Range Hopping (VRH), specifically, Efros-Shklovskii VRH for VOx, and Mott VRH for amorphous silicon. Calculation results are compared to published thermal conductance measurements based on linear approximations of the electrical conductivity temperature dependence.

We report on the effects of thermal annealing on the structural and electrical properties of Vanadium Oxide (V O_X) thin films. The annealing temperature and duration as well as the annealing environment were varied to study the effect of such variations on the V O_X film resistivity, temperature coefficient of resistance (TCR), and electrical low frequency noise (1/f). The experiments were performed with the device under different experimental conditions that include vacuum, oxygen and an inert gas (argon) environment. The device performance was studied for three annealing different temperatures: 100°C, 200°C and 250°C, with annealing times varying from 15 min to 30 min. The results show a consistent increase in resistance, with larger changes following higher temperature anneals. The influence on TCR and noise was more significant for devices annealed at 200°C or above in vacuum or in argon. X-ray diffraction studies (XRD) show that high annealing temperatures mark the onset of micro-crystallinity, with various stable and metastable phases appearing in the amorphous V O_X film matrix.

Future planetary missions call for thermal detectors with high sensitivity over a wide range of temperature or wavelength. Conventional approaches based upon photon detectors are limited to a narrow and material-selective range of wavelength, and they often require cryogenic cooling for measurements of far-infrared (FIR) radiation or very low-temperature objects, which result in a significant increase in the system’s size, weight, and power (SWaP). While thermal detectors based upon thermopiles are uncooled and sensitive to a wide range of wavelengths including FIR radiation, their sensitivity, limited by the material’s thermoelectric response and heat losses, is an order of magnitude lower than photon detectors. To address the sensitivity requirements for future planetary science missions that target very cold objects such as ice giant planets, icy regoliths, planetary satellites, and primitive bodies, we introduce a high-sensitive broadband thermopile concept using holey silicon – a thin membrane of silicon with a microfabricated arrangement of pores that can be optimized to minimize heat losses and enable breakthrough thermoelectric performance. In this paper, we present our analytical model for the holey silicon-based thermopile, its performance expectations, and its performance comparisons with the state-of-the-art thermopile technology. More specifically, we investigate the roles of thermal conductance in holey silicon-based thermopile performance, analyze the impact of thermal conduction and thermal radiation at different temperature limits, and discuss the expected significance of this prospective technology on future planetary missions.

A collimated globar source with a broadband output useful to a wavelength as long as 9 micrometers is shown and some characteristics of it are listed and illustrated. An infrared transmitting polymer Fresnel lens is used to focus this source to a small spot. A significant advantage of our polymer material’s virtually identical refractive index across both the visible and infrared regimes for our polymer material is confirmed by observing the stability of back focal length across different wavebands.

Due to the heightened awareness on global warming and ever rising energy costs, there is a need to extend solar reflective technologies beyond roofs and pavements to other surfaces such as exterior walls. The initial focus of this study is to understand and quantify the heat reflective performance of conventional exterior architectural coatings and optimizing such formulations for solar reflectance, without the use of specialty heat reflective materials. The optimized formulations are then used to quantify the enhancement of solar reflectance when formulated with commercial materials such as hollow-spherical inorganic and organic particulate fillers that are designed for this this purpose. In addition to solar reflectance, other key properties of the coatings, both at wet state and as dry films, are monitored. This will enable formulators to select solar reflective materials that will allow retention of important coating properties while providing the benefit of solar reflectance.

The established technological standards, architectures, and material choices in the realm of advanced infrared (IR) imaging has enabled the design of high-resolution and high-range IR focal plane arrays (IRFPAs) while minimizing the cost, size, weight, and power consumption of the device. HgCdTe (MCT) has also emerged as the standard choice for the IRFPA device's detector layer as semiconductor material due to its high performance-to-cost, ability to operate optimally at extreme temperatures, and access to new application domains like two-color, active, and passive shortwave infrared (SWIR) imaging. Recent work has focused on a thermomechanical-stress-aware approach for advanced integration of IRFPAs leading to the design of Modified Direct Bond Interconnect (MoDiBI) integration technology which offers the possibility to venture toward design and fabrication of small pixel pitch, large format IRFPAs with longer term operational reliability. In the thermomechanical stress aware approach, finite element modeling is used to predict the effects of cyclic thermal load on the device's components. The device's geometry and materials are optimized based on the prediction.

Hitherto, however, such thermomechanical-stress-aware design has been focused on the detector-readout assemblies. The effect of the IRFPA packaging on the overall IRFPA performance under thermal load remains underexplored. Typically, the packaging involves a Balanced Composite Structure (BCS) sandwiched between the detector chip and the base plate for improving the thermomechanical reliability. In this work, we discuss the impact material choices in BCS has on the induced thermal stresses in critical components of the detector-readout assembly. We show that for an existing intricate and non-linear interplay between the detector chip, Si ROIC, and the BCS components, it may be beneficial to tune the thickness of the Si ROIC and to consider multi-parameter geometry and material optimization for designing IRFPA and packaging assemblies with optimal thermal performance. Further, we also suggest the novel material properties within the BCS stack that yield optimal thermomechanical response in the detector chip for chosen device configurations.

Integrated longwave infrared (LWIR) photonics hold promise for enhancing on-chip molecular sensing due to the strong light-matter interaction in the LWIR spectrum, which is orders of magnitude more intense than in the near-infrared. However, conventional photonic materials suffer from high optical losses in this range. Specifically, silicon and III-V materials exhibit absorption losses due to multiphonon processes, which limit their applicability for LWIR systems. To address this issue, our work introduces a hybrid germanium-on-zinc selenide (GOZ) platform. This platform leverages the lower multiphonon absorption onset frequencies of germanium and the suitable cladding properties of zinc selenide to reduce optical losses. By employing a direct wafer bonding technique, our study achieves a waveguide system that is transparent from 2 μm to 14 μm, with measured optical losses as low as 1 cm−1 at 7.8 μm, indicating a significant improvement over traditional materials. Our findings demonstrate that the GOZ platform effectively reduces the intrinsic optical losses typical of epitaxiallygrown materials in LWIR devices, thereby paving the way for advancements in quantum and nonlinear photonic applications.

In the quest to secure the authenticity and ownership of advanced integrated circuit (IC) packages, a novel approach has been introduced in this paper that capitalizes on the inherent physical discrepancies within these components. This method, distinct from traditional strategies like physical unclonable functions (PUFs) and cryptographic techniques, harnesses the unique defect patterns naturally occurring during the manufacturing process. By employing thermo-reflectance imaging (TRI), a non-destructive evaluation technique, in this proposed method we inspect, characterize and localize defects within IC package structures such as Through-silicon Vias (TSV) and micro-bumps. TRI’s ability to detect minute temperature variations caused by defects enables the creation of a detailed map that outlines the specific locations and types of manufacturing irregularities. This novel technique leverages the uniqueness of each IC’s defect pattern to generate an inherent identifier or ’fault-mark.’ These identifiers are derived from the specific arrangement and combination of defects, making them virtually impossible to replicate or forge due to the randomness and complexity of the manufacturing process variations. The creation of these fault-marks offers a robust and tamper-resistant means of authentication, providing a reliable method for establishing proof of ownership for advanced IC packages. The implementation of this approach not only can enhance supply chain security but also acts as a deterrent against the counterfeiting of IC packages. By verifying the authenticity of ICs against a reference database of fingerprints captured during the post-silicon validation stage, stakeholders can ensure the integrity of their components. This method’s potential of using inherent fingerprinting for reliable authentication and traceability of advanced IC packages is also been discussed, thereby offering a promising solution to the challenges of counterfeiting and unauthorized reproduction in the electronics industry.

Missile Defense Agency (MDA) seeks to advance the state-of-the-art in missile seeker gimbals. Improved performance during high-g is important for the new generation of hypersonic missiles. Recent emphasis has been toward reduced size, weight and power (SWAP) systems that may be mass produced and cost effective. Ross-Hime Designs, Inc. (RHD) Minneapolis, Minnesota has met these requirements by a new patent pending, dexterous and compact gimbal architecture and rigorously adhering to a Commercial Off The Shelf (COTS) design philosophy. The gimbal is designed to accommodate electrical and cryogenic elements, assuming gimbal sensor element operation between 68-120 K. Detailed gimbal test results conclude this paper.

This report continues presentation of case studies for inverse spectral analysis and parametric modeling of diffuse reflectance spectra for NIR-SWIR absorbing dyes. These case studies demonstrate the concept of applying inverse spectral analysis to diffuse reflectance, for estimation of absorbance functions, and parametric modeling for simulation of diffuse reflectance. Sufficient sensitivity of absorption spectra relative to inverse spectral analysis establishes that estimated absorbance functions can be used for parametric modeling of reflectance from dye formulations on substrates, e.g., fabrics.

We are in the midst of the second quantum revolution. Research institutes and companies worldwide are working toward harnessing the power of quantum physics for technological applications. Gapless surface states on topological insulators are protected from elastic scattering on nonmagnetic impurities, which makes them promising candidates for low-power electronic applications. Conventional III–V infrared (IR) materials have the flexibility to engineer topologically protected surface states that can be resistant to ambient environments. In particular, largely hybridized band structures provide thermodynamically stable edge currents at the higher operating temperatures, which are important for IR sensing applications. Hence, we focused on optimizing two critical components for establishing ambient topological insulator; one for enlarging the hybridization gap, Δ, and the other for reducing bulk conduction in InAsSb/InGaSb structures. We performed a modelling study, and achieved an approximately 79 meV from InAs/InGaSb superlattices (SLs) lattice matched to AlSb, which is one of the largest reported value by far. Based on this modeling study, we selected a baseline SL design of InAsSb/GaSb on GaSb with Δ of ~62 meV to address key material issues such as finite bulk carrier conduction in undoped region of SLs. Systematic growth/processing optimization was performed in order to reduce the bulk charge carriers. The origin of constrained carrier dynamics in largely hybridized SL system and their effects on the designed topological structure were discussed.

Infrared optics technology has continued to advance in both military and civilian applications. In parallel, infrared transmitting lenses have been developed to improve the performance of infrared cameras. However, commercial Chalcogenide glass includes As or Sb which are not unsuitable for smart devices. To address this issue, novel Ge-Ga-Se ternary compositions were developed and evaluated for the lens applications. XRD was used to determine the glassforming ability. glass transition temperature was measured to determine the thermal properties. Some mechanical properties such as Knoop hardness and its coefficient of thermal expansion were performed to determine the durability of the glass. The average transmittance in the range of 8~12μm shown 60.819% and the refractive index @8, 10, 12μm were 2.51425, 2.50706 and 2.49798, respectively. The dispersion of current system shows 92.63, which is good enough to design LWIR lens.

In the current work, impact of ex-situ rapid thermal annealing (RTA) on the optical, structural and crystallographic properties of type-II InAs/GaAs(Sb) QDs heterostructures are investigated in detail. The Stranski–Krastanov (SK) QD heterostructure is grown by using solid-source molecular-beam-epitaxy (MBE) technique with 22% of Sb composition in GaAs(Sb) capping layer. The As-grown (ASG) samples are treated with RTA at temperatures of 750 _°C, 800 _°C, and 850 °C for 30 s under Ar ambient. Temperature dependent and power dependent photoluminescence (TD-PL and PD-PL) measurements are performed to investigate the impact of the emission properties of type-II heterostructures and such annealing induced changes in QD morphology, optical properties and carrier dynamics are remarkably observed due to alloy intermixing in the QD and capping interface region. The 20 K PL peak reveal a strong correlation with the annealing temperature and a strong blueshift (131 nm). The narrow linewidth from 89 nm (ASG) to 32 nm (850 _°C) is found due to an increase in the uniformity of QDs and energy states and their evolution with the RTP temperatures are analysed in detail by using deconvoluted PL peaks. Out-of-plane XRD confirms the slight reduction in hydrostatic strain with the increasing RTA temperature due to the decrease in In-content inside InAs QD. Atomic force microscopy (AFM) of uncapped QDs (surface QDs) reveals the formation of highly uniform and dense single QDs family with increasing the annealing temperature to 850 °C, which shows the good agreement with the low temperature PL result. The impact of postgrowth RTP on the InAs/GaAs(Sb) QDs heterostructures on semi-insulating epi-ready GaAs substrates has been studied extensively, and analysis of the optical properties, morphological evolution, and crystallographic change of the QDs as a function of annealing temperature show good agreement, which gives an insight for development of futuristics solar cells devices.