A survey comparing mesa delineated and planar P+/n HgCdTe infrared technologies is presented. Trades and technology limitations are explored.

Author will discuss "The Convergence Laboratory Program at Virginia Commonwealth University"

Remote sensing and characterization of high temperature targets on the Earth’s surface is required for many cross-disciplinary science investigations and applications including fire and volcano impacts on ecology, the carbon cycle, and atmospheric composition. For decades this research has been hindered by insufficient spatial resolution and/or detector saturation of satellite sensors operating at short and mid-infrared wavelengths (1-5 μm) where the spectral radiance from high temperature (>800 K) surfaces is most significant. To address this critical need, the Jet Propulsion Laboratory is developing a compact modular high dynamic range (HDR) multispectral imager concept, with the flexibility to operate in the short, mid- or long-wavelength infrared spectral bands. The goal of this project is to demonstrate this novel technology through the maturation of a mid-wavelength infrared (MWIR) imager, the Compact Fire Infrared Radiance Spectral Tracker (c-FIRST), which leverages digital focal plane array (DFPA) developed under the Advanced Component Technology (ACT) Program of the NASA Earth Science Technology Office. The DFPA is comprised of a state-of-the-art high operating temperature barrier infrared detector (HOT-BIRD) and a digital readout integrated circuit (D-ROIC), which features an in-pixel digital counter to prevent current saturation, and thereby provides very high dynamic range (>100 dB). The DFPA will thus enable unsaturated, high-resolution imaging and quantitative retrievals of targets with a large variation in temperatures, ranging from 300 K (background) to >1600 K (hot flaming fires). With the resolution to resolve 50 m-scale thermal features on the Earth’s surface from a nominal orbital altitude of 400 km, the full temperature and area distribution of fires and active volcanic eruptions and the cool background are captured in a single observation, increasing science content per returned byte. The use of a non-saturating detector is novel, overcomes previous problems where high radiance values saturate detectors (which diminishes the science content and usefulness of the data), and demonstrates a breakthrough capability in remote sensing – one with broad applicability in both terrestrial and planetary settings. By incorporating this technology, c-FIRST is suitable for quantifying emissions from fires and volcanic eruptions of different temperatures and intensities, which is critical for establishing their impact on ecosystems, carbon fluxes, and air-quality at local scales and climate at global scales. In this presentation we will discuss the properties of the c-FIRST focal plane array. The research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration. © 2023. All rights reserved.

For appropriate reconnaissance in military and security applications, comprehensive imaging is the basic prerequisite. On the one hand, this requires the use of a wide range of wavelength bands. On the other hand, a higher detector resolution results in a gain of information that can be provided to the user. On the way to highly integrated sensor technology, the use of compact and powerful optics is necessary. This presentation gives an overview of existing Hensoldt Optronics technology and gives an outlook on innovative approaches to modern imaging.

Infrared thermography has gained significant acceptance in agriculture practices for different applications ranging from crop yield estimation, fruit maturity evaluation, plants disease detection, nursery monitoring, bruise detection, irrigation scheduling, etc. The present study proposes using thermal imaging route for developing an efficient irrigation scheduling system for the horticulture plants. The conventional method of using the soil moisture sensors have many limitations, namely it indicates the water content of the soil but doesn’t indicate the actual water needs of the plant. Moreover, correct positioning of the contact sensors on the agriculture filed is also challenging task. Our proposed method aims at establishing a quantitative relationship between the thermal signature and the water stress developed in horticulture plants, through infrared thermography monitoring. The temperature measured is standardized by subtracting the ambient air temperature from mean canopy temperature. The change in the thermal signature of the leaves is a good indicator of the water needs of the plant. This observation helps us in developing a smart irrigation system.

Pixel pitch size reduction was not the focus in early infrared (IR) detector development for a long time with pixel pitch remained at 24 μm or above. Pitch size reduction today is the key enabler for cost-efficient manufacturing of large format arrays and allows compact IR-systems with high spatial resolution. When mastered the smaller pixel pitch geometries will provide consistent range performance in a smaller package, minimized aliasing and false alarm rates, ability to use faster F/# optics and shorter focal length for long range identification and optimized size, weight and power (SWaP) characteristics. Advanced integration technologies (including three-dimensional integration) are necessary to realize small pitch arrays. EPIR, Inc. has developed thermomechanical stress aware approach for advanced integration of IR focal plane arrays (IRFPAs) – MoDiBI. As intended, MoDiBI allows for favorably addressing the reliability concerns associated with the conventional integration approaches. The current work focuses on extending MoDiBI to small pixel pitch, large format IRFPA integration. Strategies for optimizing the thermal stress induced in the hybridized assembly during thermal cycling, thereby helping in reducing the fatal failures experienced by IRFPAs will be discussed. Applicability of MoDiBI to 1280×720, 8µm pitch IRFPAs will be presented.

Several MWIR nBn HgCdTe devices grown on silicon were studied. While several parameters are varied in the study, the devices can most usefully be put into 2 groups: those with a type 3 HgTe/CdTe superlattice barrier and those simply with a wider bandgap alloy barrier. Other groups have shown the potential advantage of a super-lattice barrier. Many devices were grown and fabricated, and were run through several optical and electrical tests to evaluate their properties. Utilizing the finite volume method based semiconductor device modeling software Devsim, these devices were simulated to extract further material parameters.

A compact long-wavelength infrared (LWIR) borescope imaging sensor is developed for non-contact 2D surface temperature measurements in combustor engines. LWIR detection minimizes optical interferences from hot combustion gases and soot. The borescope probe is shielded by the custom-build compact water-cooled probe housing, which can sustain flame temperature up to 2400 K at a pressure of 50 bar. The design, construction, and characterization of the sensor are discussed in detail. The developed LWIR sensor has promising applications in surface temperature measurements of engine components. This study may aid propulsion system engineers and researchers in designing thermal management systems and optimizing operation.

Case studies are presented for sensitivity analysis of absorption spectra, which are for IR absorbing dyes relative to inverse analysis of measured spectra. Inverse analysis of reflectance is based on diffuse-reflectance theory, scattering theory, and effective medium models of mixtures and deposit-on-substrate structure. Absorption spectra obtained by inverse spectral analysis provide information for estimating dielectric response functions. Sufficient sensitivity of absorption spectra relative to inverse spectral analysis implies that estimated dielectric response functions can be used for the construction of approximate effective medium models capable of estimating reflectance from dye formulations on substrates, e.g., fabrics, supporting the modeling and prediction of dielectric responses. Prototype systems considered for case-study analysis are NIR-SWIR absorbing dyes on substrates.

Copper-indium-selenide (CISe) was directly grown on n-type silicon epilayer for the photodetector application. By employing low bandgap p-CISe as the photo-absorption layer, the cut-off wavelength of the photodetector can be extended to 1309 nm, that is far longer than the cut-off wavelength (1100 nm) of Si-based photodetectors. Even though the 1550-nm-based light detection and ranging (LiDAR) system is popular for its eye-safe properties compared to the conventional 908-nm-based LiDAR system, it experiences performance degradation under heavy rain and fog. The photodetectors responsive to 1300-nm-light are interesting because 1300-nm-based LiDAR system is less vulnerable to water absorption than 1550-nm-based system and is safer to human eye than 908-nm-based system. Furthermore, p-CISe/Si heterostructure enables the monolithic integration of near-infrared photodetector with Si-based readout circuit.

As the need for infrared phosphors increases in the field of medical diagnosis, food analysis, biological imaging and machine vision, various infrared materials are being researched. Here, we reported CaAl12O19:Cr3+, Cr4+(CAO) phosphor that successfully synthesized by solid-state synthesis method. Among the five Al sites of CAO phosphor, two activators (Cr3+ and Cr4+) are doped into two different Al sites (Al4 (octahedral), Al3 (tetrahedral)). Excited by 414 nm or 577 nm, the CAO phosphor emits a two sharp spectrum (689, 1389 nm) and two broadband spectrum (700 to 1000, 1400 to 1800 nm). Each spectrum peaks were classified into an activator and its energy level transfer according to the Tanabe Sugano diagram. Through this, the luminescence mechanism of CAO was accurately analyzed and the energy level of Cr4+ hidden by Cr3+ luminescence was also confirmed.