Infrared Sensors, Devices, and Applications XIV

This study describes 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.

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. 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. 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. 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 glass-forming 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.

We demonstrate a multi-band infrared photodetector with 9 channels in the 1.6-2.4 μm range by integrating a Fabry-Perot based multi-bandpass filter onto an extended-InGaAs infrared photodetector. This multi-bandpass filter features an array structure with 3x3 (9 bands) different cavity thicknesses. The thickness variation is achieved through a single photolithography process, followed by a photoresist reflow process and etching. After forming the 9-band filter on the extended-InGaAs epitaxial wafer, a photodiode(PD) process was employed to fabricate a 3x3 array PD on a single chip. The fabricated PD exhibited a 9-band spectrum in the 1.6-2.4 μm range, with a full width at half maximum (FWHM) ranging from 40-70 nm for each band.

Two-dimensional modeling of AlInAsSb mid-wave infrared waveguide avalanche photodiodes is presented in this work. The waveguide coupling is investigated based on the beam propagation method. The APD photon-response and impact ionization are further simulated based on a drift-diffusion theory. The frequency response and bandwidth are also evaluated. Modeling results of I-V curves, multiplication gain, breakdown voltage, excess noise factor, -3dB bandwidth and gain-bandwidth product are presented with some comparable to the experimental report from other researchers. Design optimization is also explored together with results discussion.

Impact of ex-situ RTA treatment on the optical, structural and crystallographic properties of type-II InAs/GaAs(Sb) S-K QDs heterostructures with 22% of Sb-composition is investigated extensively in the current work. The 20 K PL peak reveal a strong correlation with the annealing temperature and a strong blueshift (131 nm) for 850 oC RTA sample with narrow linewidth. XRD confirms the slight reduction in hydrostatic strain with the increasing RTA temperature due to the decrease in In content inside InAs QD, whereas, AFM of uncapped QDs reveals the formation of highly uniform and dense single layer QDs. Thus, all the optical and structural properties of RTA treated InAs/GaAs(Sb) QDs suggest that such heterostructures can be a potential candidate for improving the solar cell performance in future.

The human respiration rate (RR) is a vital physiological parameter, used to determine human health. However, it is clinically the most undocumented sign, owing to the shortcomings of existing contact RR monitoring techniques. Hence, there is a growing demand for a non-contact, and reliable alternative to monitor human health. The present work implements passive IRT, to monitor the human RR in a contactless and non-invasive manner. The previous studies have exclusively focused on the manual determination of the breaths per minute (BPM), in the thermal BS. In the present work, a novel "Breathing Signal Characterization Algorithm" (BSCA) is developed to determine the BPM and identify every breath in the thermal BS as regular, prolonged, or rapid, using machine learning (ML). To the best of our knowledge, this is the first work that reports the use of ML to determine the BPM and characterize the breaths in the thermal BS.

Infrared (IR)-to-visible up-conversion device allows a low cost, pixel-free IR imaging over the conventional expensive compound semiconductor-based IR image sensors. However, the external quantum efficiency (EQE) has been low due to the integration of an IR photodetector and a light-emitting diode (LED). Here, by inducing a strong micro-cavity effect, we demonstrate a highly efficient top-emitting IR-to-visible up-conversion device where PbS quantum dots IR-absorbing layer is integrated with a phosphorescent organic LED. By optimizing the optical cavity length between ITO/thin Ag/ITO anode and semi-transparent Mg:Ag top cathode, our up-conversion device yields 7.6 % of photon-to-photon conversion efficiency from the top-emission. The high efficiency could be achieved under a low IR transmission through the semi-reflective anode, resulting in an internal quantum efficiency over 63 %. Finally, pixel-free IR imaging is demonstrated using the up-conversion device, boosting the effect of micro-cavity on the brightness and the contrast of an IR image.

In the proposed work, we focused on creating a tunable coupler in the selected range using additional materials controlled by an electric field, we focus on the influence of only the change of power in a coupled arm. The tunable coupler's construction consists of simultaneously making two tapered optical fibres and placing them in a liquid crystal cell with LC 6CHBT.Our work shows the first experimental study on constructing the presented coupler for selected wavelengths using multimode optical fibers and liquid crystal 6CHBT. The LC cell with tapers was steering with a voltage from 0-200V. Additionally, the electric field was modulated with a frequency of 1-5Hz to observe the possibility of fast tuning of the division ratio in a new coupler. The first results show that it is possible to create a new tunable coupler by setting the appropriate technological parameters.

Leonardo DRS has a consistent track record of extending the boundaries of electro-optical infrared imaging, both enabling advanced capabilities and making them accessible through scalable production techniques. From a retrospective of innovations, this talk will extend to active development and discuss the outlook for future advancement at Leonardo DRS.

Space-qualified midwave infrared (MWIR) camera systems have been high in cost and proprietary to large aerospace companies. To achieve high frame rates, the power consumption is also high. The smaller pixels used in larger arrays have low charge handling capacity that results in poor signal to noise performance. This is a significant obstacle for many small satellite missions. This paper presents a novel, low SWAP-C, commercially available high-end MWIR camera technology that is fully space-qualified for LEO missions. The design uses high-end commercial infrared detectors and coolers combined with custom circuitry for smart power management of cryo-coolers and latch-up protection of the detectors.

New nano- or micro-patterned metal nonlinear metasurfaces, robust against temperature and more sustainable than current IR materials, could respond across the LWIR-to-SWIR spectrum (no band gap) for long-distance data/power transfer, thermal management, sensing, navigation, and detection. In this presentation, we discuss our recent discovery of longitudinal and transverse optical rectification (OR) in an asymmetric plasmonic grating that is inherently linear. A periodic Au stripe array breaks inversion symmetry perpendicular to the stripes, so that direct (zero frequency) electronic, rectified current, due to selective excitation of only one SPP mode, flows with incident photons polarized perpendicular to the stripes. We also measured the influence of the photon helicity on the OR current, from coupling of the spin of propagating surface plasmon-polaritons (SPPs) to their linear momentum and to the angular momentum of incident photons. It is interesting that bosonic SPPs generate this electrical current. Simple ‘photon drag’ and other models of electronic current do not completely explain the experiment. We discuss scientific advances to better understand these phenomena.

We describe the performance of long-wavelength MCT operating at 4.2K as a fast photoconductive detector for far-infrared nanospectroscopy. The technique employs scattering from the tip of an atomic force microscope (AFM) engaged with a sample surface while in "tapping mode" at a frequency f, with the scattered infrared sensed at a higher harmonic, e.g. 2f, 3f or even 4f to improve spatial discrimination. With typical tapping frequencies >100 kHz, the infrared detector requires a bandwidth of 1 MHz or higher, for which thermal-type IR detectors are not sufficiently fast. MCT detectors are usually limited to wavelengths shorter than 25µm when operating at T=77K, but this can be overcome by cooling to 4.2K, in which case the detection threshold wavelength extends to beyond 50 microns. An additional benefit is an overall 5X improvement in S/N. *This work supported by the U.S. Department of Energy under contract DE-SC0012704 at NSLS-II and BNL. See ACS Photonics, 10, 4329-4339 (2023), (https://doi.org/10.1021/acsphotonics.3c01148)

Methane is a greenhouse gas that has a global warming potential (GWP) of 25 relative to carbon dioxide. 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. 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 of heat transfer in microbolometer based infrared imaging systems. The thermal conductance G can be measured by monitoring the microbolometer temperature change (T-T0) induced by a known power excitation P, from a source such as an (electrical) pulse, or due to constant voltage or current Joule heating at thermal equilibrium, with P = G(T-T0). 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 details and results will be presented and compared to published thermal conductance measurements based on linear approximations of the electrical conductivity temperature dependence.

The integration of autonomous drones with light-weight, low-cost hyperspectral sensors and real-time machine learning capabilities heralds a new era in remote sensing technology. This combination of technologies captures light within the visible to Shortwave Infrared spectrum and uses advanced Artificial Intelligence to perform real-time, in-situ object classification at the edge. The use of autonomous flight enhances both the performance of the sensor and the ability of the operators to respond to dynamic conditions and information requirements. The system’s data services will enable new approaches to solving spectral un-mixing, high-precision object detection and condition-class assessments for enhanced situational awareness and target detection. The sensor’s performance and price point will drive new opportunities that expand the use of hyperspectral imaging for environmental monitoring, disaster response, precision agriculture, and infrastructure monitoring. Our paper will discuss the sensor’s novel design that make it suitable for small unmanned aerial vehicles, the real-time data analytics service, and the drone integration for autonomous flight.

We report on the effects of thermal annealing on the structural and electrical properties of Vanadium Oxide (VOx) thin films. The annealing temperature and duration as well as the annealing environment were varied to study their influence on resistivity, temperature coefficient of resistivity (TCR), and noise. The experiments were performed with the device under vacuum and in an inert gas (argon) ambient, at temperatures ranging from 100o C to 250 o C and 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 o C or above in vacuum or in argon. X-ray diffraction studies (XRD) show that high annealing temperatures mark the onset of micro-crystallinity.

Polycrystalline lead selenide thin film has now emerged as a promising choice for low-cost and uncooled MWIR detectors and arrays operating at room temperature within the 3~5 µm wavelength range. LCDG (Laser Components Detector Groups) has successfully fabricated a new version of PbSe thin films using the chemical bath deposition (CBD) method on quartz substrates, enabling the development of infrared detectors and arrays with robust and high production yield. To achieve efficient activation of the PbSe thin film, LCDG investigates PbSe material from chemical reaction of the bath deposition to final packaging to meet various customer specifications and establishes PbSe detectors based on nano- and micro-particles embedded PbSe thin film, resulting in exceptional MWIR photoconductive response at room temperature. The characterization of PbSe thin film reveals the presence of various nanostructures, such as nano- and micro-particles as well as Pb-oxide phases and Pb-iodine phase carrier transporting channels. This paper reports the MWIR performance of the uncooled LCDG’s PbSe detector, focusing on responsivity, EQE, 1/f noise and FTIR spectral response (77K-340K), and D*.

High-sensitivity broadband thermal detection is crucial for various applications, ranging from temperature sensing for humans, including crowd surveillance, temperature screening, pedestrian detection, occupancy detection, and human motion monitoring, to measurements of cold objects such as icy regolith on the Moon or primitive bodies in space. While thermal detectors based on thermopiles have unique advantages over photon detectors for measuring cold objects, the performance of conventional thermopiles is often limited by the material’s thermoelectric response and heat losses. Here, we introduce a novel thermopile detector architecture based on holey silicon. Holey silicon is a thin membrane of doped 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 holey silicon-based thermopile detector concept, performance expectations based on the analytical model, and performance comparisons with state-of-the-art thermopile technology.

The emissivity, reflection, or transmittance of media in the infrared can be measured using a filter spectrometer, which typically consists of an incandescent light source, filters, and one or more detectors. In the case of a focal-plane array of detectors, this configuration can be a multispectral or hyperspectral camera. We demonstrate that the spectral resolution of this simple system can be significantly improved when the temperature of the incandescent source is varied and tracked, i.e. via “Planck enhancement”.

This talk shows the recent development of linear and Geiger-mode pseudo-planar Ge-on-Si avalanche photodiodes (APDs) in the short-wave infrared region. We demonstrate a 26 µm-diameter Ge-on-Si Geiger-mode APD with an extremely low noise-equivalent-power of 7.7 × 10−17 WHz−½ and a jitter value of 134 ± 10 ps at 1310 nm wavelength and at 100 K operating temperature. We demonstrate that a linear array of Ge-on-Si linear mode APDs comprising of 12 pixels shows high responsivity, highly uniform avalanche breakdown voltage and avalanche gain at 1550 nm wavelength and at room temperature.

Two infrared sources are shown and some characteristics of each are listed and illustrated. One is a very low power CO2 laser, tunable over a small range, and the other is a collimated globar source with a broadband output useful to a wavelength as long as 9 micrometers. An infrared transmitting polymer Fresnel lens is used to focus each source to a small spot.

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.

Ferroelectric hafnium zirconium oxide (HZO) has potential as a building block material for future infrared detectors. This study focuses on developing the design space of ultrathin 10 nm titanium nitride (TiN) / 10 nm HZO / 10 nm TiN pyroelectric detectors and bolometers. We demonstrate proof-of-concept pyroelectric detectors with an operating range starting at 1.6 kHz and surpassing 10 kHz, and a responsivity of up to 1.9×10-2 nA/µW. Furthermore, we explore the possibility of integrating a pyroelectric detector element with a molybdenum disulfide (MoS2) transistor as a floating-gate field effect transistor (FG-FET) to enable DC to sub – 1 ms bandwidth devices with large temperature coefficient of resistance (TCR) useful for sensitive, lower power operation. At subthreshold, a fabricated device had a TCR between -0.065 K-1 and -0.051 K-1 on the forward gate voltage sweep and between -0.03 K-1 and -0.04 K-1 on the reverse voltage sweep.

A two-color p-i-n detector with a wide continuous spectral response from 400 nm to 2600 nm wavelength is discussed in this paper. The sandwich detector can be operated under reverse bias with linear response behavior. We shall present characteristics of a sandwich detector capable of sensing UV to SWIR wavelengths with a coincident field of view. These detectors demonstrate linear behavior along with the wide optical dynamic range required for their successful application in spectrophotometers, flame monitors and non-contact radiation thermometers.

The untested application domains and operating conditions of the HgCdTe based IRFPAs has emphasized the need to address the effect of cyclic thermal load and the ensuing reliability concerns of conventional IRFPA architectures and integration approaches. This work highlights the importance of thermomechanical-stress-aware device optimization factoring in the interfaces, contacts and materials present in the entire device assembly, including the packaging.

Our work introduces a germanium-on-zinc selenide (GOZ) platform to address the need for low-loss materials in longwave infrared (LWIR) integrated photonics. The LWIR range is critical for sensing applications due to distinctive molecular absorptions. Our approach utilizes bonding of germanium thin films to zinc selenide substrates, facilitating transparency from 2 μm to 14 μm and achieving optical losses of 1 cm−1 at 7.8 μm. This platform provides an alternative to traditional epitaxially-grown materials, potentially broadening the scope of applications in quantum and nonlinear photonics.

Modern deep learning methodologies have shown a clear potential for automatically detecting weapons in CCTV images. The most advanced methodologies not only consider the appearance of the weapon but also analyze the individual's body pose, crucial in scenarios with poor lighting and distant cameras. This study explores the use of a portable thermal camera, potentially carried by police officers, coupled with artificial vision to detect concealed weapons. The thermal signal attenuation caused by the weapon can be automatically detected, as demonstrated through extensive experiments. The research introduces a novel dataset labeled for this purpose, contributing to the research community. The practical use of the system as a body-worn camera is evaluated.

Metamaterial perfect absorbers (MPAs) are subwavelength structures offering powerful light/matter interaction characteristics: high spectral resolution, tunable absorption, polarization insensitivity, and angle independence. Numerical and analytical simulations show over 98% absorption in the mid-infrared (MID-IR) with a narrow FWHM of 4%. This technology could pave the way for cost-effective and compact hyperspectral MID-IR filters, making the "spectral fingerprint region" more accessible for atmospheric sensing.

Infrared photodetection at ambient temperature is a challenge that classical photodetectors have not been able to fulfill yet. New materials, like the 2D materials family, and plasmonic nanostructures, are currently explored to address this challenge. We will show how the combination of carefully design coupled Fabry-Perot nanoresonnators and graphene can be used has an ambient infrared photodetector.

This work proposes a novel method to enhance the security of advanced integrated circuit (IC) packages supply chain by exploiting their inherent physical discrepancies to create unique identifiers. Unlike traditional approaches such as physical unclonable functions (PUFs) or cryptographic techniques, this strategy uses Thermo-reflectance imaging (TRI) to detect unique defect patterns within the ICs, such as through-silicon vias and micro-bumps. These defects serve as an inherent identifier or 'fault-mark,' providing a tamper-resistant means of authentication and proof of ownership. The technique's non-replicability ensures supply chain security and integrity by allowing for the verification of IC authenticity against a reference database.

Optical sensors for water quality monitoring are discussed in this paper where new optical tools for real-time water quality diagnostics without the use of traditional sampling and laboratory physico-chemical analysis are presented. In particular, the optical decision-making system is being developed as an operational tool for the in-situ assessment of water quality in natural water reservoirs. Several versions of this system are analyzed using multi-channel spectrophotometers and spectroellipsometers. The spectral images taken by these devices are the basis for diagnosing water quality using new algorithms for recognizing these spectral images. More precisely, algorithms are being developed to identify optical spectral images of water objects. In particular, this paper provides introductory remarks in the subject of the optical tools for water quality monitoring and then presents details on the spectrophotometry and spectroellipsometry methods, the optical sensors for water quality monitoring.

Wound Healing by Laser Therapy - • Background: In 1967 a few years after the first working laser was invented, Endre Mester in Semmelweis University Budapest, Hungary wanted to find out if laser might cause cancer. He took some mice, shaved the hair off their backs, divided them into two groups and gave a laser treatment with a low powered ruby laser to one group. They did not get cancer and to his surprise the hair on the treated group grew back more quickly than the untreated group. That was how "laser biostimulation" effects were discovered. (Effect of laser on hair Growth of mice (in Hungarian). Mester, E. Szende, B. and Tota, J.G. (1967). Kiserl Orvostud 19. 628-631). • Purpose of the work: The effects of pulsed monochromatic light, with fixed pulsations and wavelengths, on the healing of pressure ulcers were evaluated in this prospective, randomized, controlled study. • Method: A placebo-controlled, double-blind study using low energy photon therapy (LLLT) was performed in ten patients with bedsore on the back. Treatment was given three times a week for 10 weeks, using monochromatic (red) optical sources; diode 660nm (GaAl-660). The patients who were randomized to plac

Electroluminescence in mid-IR of hBN-encapsulated graphene under large bias was recently put into evidence through spectroscopy and noise thermometry. We demonstrate in this presentation that hyperbolic phonon polariton electroluminescence is responsible for efficient out-of-plane energy transfer through hBN. We then show that this energy transfer can be engineered using hBN with various turbidity, exhibiting for the first time that far-field energy transfer in turbid media remains valid in the case of energy transfer by confined hyperbolic rays.

When an intense laser interacts with a gas of atoms, high-order harmonics are generated. In the time domain, this radiation forms a train of extremely short light pulses, of the order of 100 attoseconds. Attosecond pulses allow the study of the dynamics of electrons in atoms and molecules, using pump-probe techniques. This presentation will highlight some of the key steps of the field of attosecond science.

With 140+ petabytes of historical data holdings, 3.8 million square kilometers of daily multi-spectral collection, integration of Synthetic Aperture Radar and newly launching assets every quarter, the opportunities to develop insight from sense making technologies at Maxar are ever growing. During this discussion, we will cover the challenges of collecting, organizing, and exploiting multi source electro-optical remote sensing systems at scale using modern machine learning architectures and techniques to derive actionable insights.