This PDF file contains the front matter associated with SPIE Proceedings Volume 11129 including the Title Page, Copyright information, Table of Contents, Introduction, and Conference Committee listing.

The valley-dependent skew scattering of conduction electrons by impurities in two-dimensional α-T₃ materials is studied. The interplay of Lorentz and Berry forces, which act on mobile electrons in position and momentum spaces respectively, is quantified. Interactions of electrons with ionized impurities at two valleys are observed in different scattering directions. Both the zeroand first-order Boltzmann moment equations are used for calculating scattering-angle distributions of resulting skew currents, which are significantly enhanced by introducing microscopic inverse energy- and momentum-relaxation times to two moment equations.

Low dark current and/or high operating temperature are the main motivations behind the nBn detector structures where removing the valence band discontinuity is usually an important design challenge. With the utilization of the bias polarity, these structures can also be easily designed as dual-band detectors and in this study, a dual-band (MWIR / LWIR) HgCdTe nBn detector configuration has been numerically examined. Valence band barrier suppression has been obtained with the delta-doped and compositional graded layers similar to the recent single band studies.

Polycrystalline thin films of (Sb_0.42Bi_0.58)₂Se₃ are prepared by co-evaporation in a two-step process. First, the semiconducting layer is grown at 240°C. Subsequently the films are annealed in-situ at various temperatures. The incorporation of Bi into the orthorhombic Sb₂Se₃ system reduces the bandgap and thus widens the range for infrared detection. It is found that thin film layers can be prepared single phase, while a decomposition is observed for temperatures exceeding 440°C, where the rhombohedral structure of Bi₂Se₃ forms in addition. Photoluminescence measurements show an increased optoelectronic quality of the films with increasing annealing temperature. However, the luminescence signal reduces when the films decompose into the orthorhombic and the rhombohedral phases.

The 6.1 Å family of Sb-based III-V materials and heterostructures is a promising candidate for infrared (IR) detector applications. For the realization of low-cost, large-format IR photodetector arrays these materials must be grown on larger diameter substrates. For this purpose, GaAs substrates, with appropriate metamorphic buffer structures, have shown to be a promising alternative. Moreover, other platforms, such as Ge-on-Si (Ge/Si) and Ge-on-insulator-on-Si (GeOI/Si) virtual substrates, enable direct integration of the III-V devices with Si microelectronics read-out and processing architectures. In this paper, we investigate the structural and optoelectronic quality of mid-wavelength infrared InAsSb nBn photodetectors with a room temperature 50% cut-off wavelength of 4.5 μm grown on multiple substrates, including GaSb, GaAs, and Ge/Si. Material quality was examined using non-contact, non-destructive electron channeling contrast imaging (ECCI) in a scanning electron microscope for high-accuracy threading dislocation density (TDD) measurement and time-resolved microwave reflectance (TMR) spectroscopy for minority carrier lifetime (τ_mc) measurement. The combination of these two techniques enables a direct correlation between TDD and τ_mc. Our preliminary data indicate that higher TDD results in a reduced lifetime, similar to observations in III-V materials and HgCdTe IR materials. Here we present our analysis of equivalent nBn structures grown on GaSb, GaAs, and Ge/Si. The results of τ_mc indicate that the sample on GaSb and GaAs have the longest and the shortest lifetime, respectively, for temperatures above 70 K. Combining lifetime characterization with the TDD analysis from ECCI enables the assessment of metamorphic detectors on alternate substrates as a platform for large-format focal plane arrays.

A high-performance graphene-based HgCdTe detector technology is being developed for sensing over the mid-wave infrared (MWIR) band for NASA Earth Science, defense, and commercial applications. This technology involves the integration of graphene into HgCdTe photodetectors that combines the best of both materials and allows for higher MWIR (2-5 μm) detection performance compared to photodetectors using only HgCdTe material. The interfacial barrier between the HgCdTe-based absorber and the graphene layer reduces recombination of photogenerated carriers in the detector. The graphene layer also acts as high mobility channel that whisks away carriers before they recombine, further enhancing the detector performance. Likewise, HgCdTe has shown promise for the development of MWIR detectors with improvements in carrier mobility and lifetime. The room temperature operational capability of HgCdTe-based detectors and arrays can help minimize size, weight, power and cost for MWIR sensing applications such as remote sensing and earth observation, e.g., in smaller satellite platforms. The objective of this work is to demonstrate graphene-based HgCdTe room temperature MWIR detectors and arrays through modeling, material development, and device optimization. The primary driver for this technology development is the enablement of a scalable, low cost, low power, and small footprint infrared technology component that offers high performance, while opening doors for new earth observation measurement capabilities.

The Short and Mid Wave InfraRed (S-MWIR) rugged active detection system has been designed to be operated in the worst conditions with very low Size Weight and Power (SWaP) factor. The detection system is based on a single uncooled detector device implementing a Lead Sulphide (PbS) (SWIR) and Lead Selenide (PbSe) (MWIR) plate cells on the same package and an emitter based on a combination of standard silicon materials with Nano Amorphous Carbon (NAC) membrane. The data acquisition and processing have been configured to handle very low signal values and important noise in the ambient. The detection system is based on a Lock-In Amplification tuned on 10Hz frequency to reduce the noise effect. The low operation frequency reduces the requirements on IR source and sampling electronics. The IR detectors and source has been instrumented with thermistors and the responsivity of the system has been characterized for non-thermal controlled operation. The characterized responsivity and the instantaneous temperature shall be considered on the data retrieval. The detection system has been qualified for very tough environment as very low temperature (-135°C) and relatively high temperatures (70°C) for a year continuous operation, high vacuum (10^-6 mbar), high mechanical vibration and shock and high radiation levels. The S-MWIR detection system has been implemented on the Dust Sensor for the ExoMars’20 mission for operation from 10°C to -90°C with two detector systems forward and backward for calculation the in-situ dust concentration on Mars surface.

In oil and gas fields, gas leakage is one of the major concerns, as it causes serious economical, safety, and health consequences. This requires a frequent and periodic inspections of all equipment which either store or transport gases, such as gas pipelines and gas storage tanks. In this paper, a real-time leak detection and localization system which can operate fully autonomously either in a drone or a mobile robot is suggested. The apparatus has the advantage of remotely detecting leaks even in case of humid weather, situation for which most recent leak detection systems such as Long wave Infrared (LWIR) and Medium wave IR (MWIR) fail. The system consists of a Short wave IR (SWIR) camera to remotely detect the existing of leaks even in case of humid weather or during the rain. In addition, the system is not sensitive to thermal radiations which is the case of LWIR and MIIR radiations. A CCD camera, together with a set of sensors that include an Inertial Measurement Unit (IMU) and global positioning system (GPS) are used to accurately determine the location of the leak using image correlation and triangulation techniques. A series of extensive experimental tests demonstrate the capability of the system to detect different types of gas leaks for different scenarios. This leads to state that the suggested system can be a tangible alternative for next generation leak detection systems.

Long-wavelength infrared (LWIR) focal plane arrays (FPAs) needed for Earth Science imaging, spectral imaging, and sounding applications have always been among the most challenging in infrared photodetector technology due to the rigorous material growth, device design and fabrication demands. Future small satellite missions will present even more challenges for LWIR FPAs, as operating temperature must be increased so that cooler (and radiator) volume, mass, and power can be reduced. To address this critical need, we are working on following three technologies. 1) Type-II superlattice (T2SL) barrier infrared detector (BIRD), which combines the high operability, spatial uniformity, temporal stability, scalability, producibility, and affordability advantages of the quantum well infrared photodetector (QWIP) FPA with the better quantum efficiency and dark current characteristics. A mid-wavelength infrared (MWIR) T2SL BIRD FPA is a key demonstration technology in the (6U) CubeSat Infrared Atmospheric Sounder (CIRAS) funded under the ESTO InVEST Program. A LWIR T2SL BIRD FPA is also being developed under the ESTO SLI-T Program for future thermal infrared (TIR) land imaging needs. 2) The resonator pixel technology, which uses nanophotonics light trapping techniques to achieve strong absorption in a small detector absorber volume, thereby enabling enhanced QE and/or reduced dark current. 3) High dynamic range 3D Readout IC (3DROIC), which integrates a digital reset counter with a conventional analog ROIC to provide a much higher effective well capacity than previously achievable. The resulting longer integration times are especially beneficial for high flux/dark current LWIR applications as they can improve signal-to-noise ratio and/or increase the operating temperature. By combining the aforementioned technologies, this project seeks to demonstrate a cost-effective, high-performance LWIR FPA technology with significantly higher operating temperature and sensitivity than previously attainable, and with the flexibility to meet a variety of Earth Science TIR measurement needs, particularly the special requirements of small satellite missions.

In this work, we design and produce 1280x1024 format InGaAs based planar type detectors with 15μm pixel pitch. We have obtained diffusion current limited low dark current (~10fA) and high responsivity (1.08A/W at 1.55μm) values at room temperature conditions. Moreover, dark current modeling is performed using diffusion, generation and recombination (GR) and trap assisted tunneling (TAT) current mechanisms. Ideality factor is extracted from forward bias characteristics. Excellent match between modeling and experimental data is reached. Also, temperature dependency of dark current is studied in 10°C – 60°C ranges. The area and perimeter related dark current components are differentiated using test detectors with changing diameters that are placed next to the detector array structure. Experimental data shows good agreement with theoretical expectations.

At present, InGaAs and HgCdTe are still the primary choices of materials for 1-3μm short wavelength infrared (SWIR) photodetectors (photodiodes). Besides lattice matched 1.7μm cutoff standard InGaAs photodetectors, demands for extended wavelength (EW) InGaAs photodetectors (1.9-2.6μm cutoff) continue to grow in a broad range of markets such as Internet-of-Things (IoT), gas sensing, food processing, etc. This paper reviews recent progress in EW InGaAs photodetectors at Teledyne Judson Technologies (TJT). For 1.7μm cutoff at room temperature, InGaAs detectors generally have higher performance (lower dark current and higher shunt resistance) than the conventional SWIR HgCdTe detectors as characterized by the famous Rule-07 formula. In contrast, up to just recent years, EW InGaAs detectors generally had performance below the corresponding SWIR HgCdTe per Rule-07 for the same cutoff wavelength and operating temperature. The performance gap between the two materials became larger as the cutoff wavelength increases. This performance difference is primarily due to the lattice mismatch or strain induced defects in EW InGaAs materials. However, the recent progress in both EW InGaAs material growth and detector fabrication has resulted in dramatic improvement of EW InGaAs detector performance. The performance gap between the two materials is becoming much smaller or negligible at some wavelengths, while at other wavelengths, EW InGaAs even exceeds SWIR HgCdTe per Rule-07. In this paper, we will present recent detector performance data taken from EW InGaAs, as well as SWIR HgCdTe photodetectors, manufactured at TJT through state-of-the-art technologies. These discrete frontside illuminated detectors have sizes ranging from <0.25mm up to 5mm dia. and operate at temperatures from thermoelectric cooled (TEC, -20°C to -85°C) to above room temperature. An in-depth analysis of dark current density at reverse biases, as well as shunt resistance-area product at zero bias (R0A), over a broad temperature range, is performed. The data is compared with Rule-07 over the wavelength and temperature ranges of interest. Other detector performance parameters, such as spectral responsivity (quantum efficiency) and capacitance, are also compared between the two materials.

The shorter wavelengths of the ultraviolet (UV) band enable detectors to operate with increased spatial resolution, variable pixel sizes, and large format arrays, benefitting a variety of NASA, defense, and commercial applications. Al_xGa_1-xN semiconductor alloys, which have attracted much interest for detection in the UV spectral region, have been shown to enable high optical gains, high sensitivities with the potential for single photon detection, and low dark current performance in ultraviolet avalanche photodiodes (UV-APDs). We are developing GaN/AlGaN UV-APDs with large pixel sizes that demonstrate consistent and uniform device performance and operation. These UV-APDs are fabricated through high quality metal organic chemical vapor deposition (MOCVD) growth on lattice-matched, low dislocation density GaN substrates with optimized material growth and doping parameters. The use of these low defect density substrates is a critical element to realizing highly sensitive UV-APDs and arrays with suppressed dark current under high electric fields. Optical gains greater than 5×10⁶ with enhanced quantum efficiencies over the 350-400 nm spectral range have been demonstrated, enabled by a strong avalanche multiplication process. Furthermore, we are developing 6×6 arrays of devices to test high gain UV-APD array performance at ~355 nm. These variable-area GaN/AlGaN UV-APD detectors and arrays enable advanced sensing performance over UV bands of interest with high resolution detection for NASA Earth Science applications.

A theoretical analysis and implementation of a high sensitivity infrared thermometry system for a precise real-time temperature control in domestic induction cooktops is presented. The temperature in the cookware constitutes the control variable of the closed-loop power control system implemented in a commercial induction cooktop. The system includes an InGaAs PIN photodiode and a differential preamplifier which detects the infrared radiation (IR) emitted from the bottom of the cookware and the glass-ceramic top. The analysis includes an algorithm to discount the contribution of the glassceramic material from the total signal. In an infrared thermography application where an IR sensor is used, measuring the object’s surface emissivity is crucial because it significantly impacts the temperature measurement result. For a precise temperature control with a maximum temperature error of 5°C in all range of cooking temperatures (60°C to 250°C) a cookware emissivity measurement system is included. The accuracy and the validity of our model have been tested and confirmed with measurements performed with the proposed system. The experimental arrangement built to test the proposed system has validated the usefulness of the IR thermometry system applied to the cookware within the range of cooking temperatures from 60°C to 250°C, making it suitable for this application. It has been proved that the IR sensor and the associated electronic works properly in a high-temperature environment such as a real induction heating cooktop.

A diamond-like carbon thin film was deposited on the outer face of the germanium (Ge) window to protect the infrared lenses from a harsh environment in automotive application. Infrared transmittance and residual stress of a tetrahedral amorphous carbon (ta-C) thin film by a filtered cathodic vacuum arc (FCVA) source were investigated to increase the lifetime of a Ge window. They were found to have a trade-off relation about the change of the substrate pulse voltage. By introducing methane gas in FCVA deposition process, a hydrogenated ta-C (ta-C:H) thin film of which both IR transmittance and residual stress was improved could be obtained. A Ge window coated with ta-C:H thin film with 1.43 μm thickness showed anti-reflective effect in long-wave infrared. The hardness of ta-C:H thin film on Ge window was higher than 30 GPa. Adhesion, severe abrasion, temperature, humidity and salt solubility tests were carried out in accordance with MIL-C-48497A.

Infrared (IR) technology plays a critical role in various military and civilian applications including target acquisition, surveillance, night vision, and target tracking. IR sensors and systems operating from the short-wave infrared (SWIR) to long-wave infrared (LWIR) spectra are being developed for defense and commercial system applications. Performance of these IR systems is substantially limited by signal loss due to reflection off the IR substrates and optical components. Optical coatings with high antireflection (AR) characteristics can overcome this limitation and thus enhance the performance of IR systems. We are developing and advancing high-performance antireflection (AR) coatings for a wide range of spectral bands on various substrates for a variety of defense and commercial applications. The AR coatings enhance the transmission of light through optical components and devices by significantly minimizing reflection losses, providing substantial improvements over conventional thin-film AR coating technologies. The optical properties of ARcoated optical components and sensor substrates have been measured and fine-tuned to achieve high levels of performance. In this paper, we review our latest work on robust nanostructure-based AR coatings, including recent efforts in the development of the nanostructured AR coatings on silicon and CdZnTe substrates as well as on ZnSe lenses.

Astronomical instrumentation is traditionally costly, large, and alignment-sensitive owing to the use of bulk optics. The use of integrated photonic devices in astronomical instrumentation can mitigate such drawbacks in certain applications where high light throughput and spectral bandwidth are less crucial. In this work, we present an ultra-compact carbon dioxide detection scheme using a single silicon waveguide ring resonator. The comb-like absorption line spectrum of CO2 around 1580 nm wavelength can closely match the comb spectrum of an appropriately designed ring resonator. By actively correlating such a ring spectrum with the CO2 absorption lines, a specific detection signal can be generated. We design the free spectral range of a ring resonator to match the absorption line spacing of carbon dioxide lines in the range from 1575 to 1585 nm. Using thermo-optic modulation, the ring resonator drop or through port transmission spectrum can be shifted back and forth across the incoming CO2 light spectrum, resulting in a modulated signal with an amplitude proportional to the CO2 absorption line strength. Furthermore, high frequency modulation and lock-in detection can result in a significant improvement in the signal to noise ratio. We demonstrate that such a device can provide real-time carbon dioxide detection for applications in ground- and satellite-based astronomy, as well as remote atmospheric sensing, in a compact package. In future work, such a sensor can be adapted to a range of gases and used to determine radial velocities and compositional maps of astronomical objects.

We have successfully tested 5 to 8 GHz bandwidth, uncooled, Extended InGaAs 2.2 μm wavelength, linear optical receivers, coupled with single mode fibers for 30 MeV Protons, Gamma rays, 1 GeV/n Iron ions, and 1 GeV/n Helium ions. These devices find multiple applications in outer-space for coherent rapid Doppler shift LIDAR, long wavelength gravitational wave sensing, as well as inter-planetary and Earth-to-Moon coherent communication links. Nine devices comprising of Extended InGaAs 2.2 μm PIN photodiode (PD) and GaAs transimpedance amplifiers (TIA), coupled with single mode fibers, were tested with 30 MeV protons, three each with fluence levels of 4.9 × 10¹⁰ cm^-2 , 9.8 × 10¹⁰ cm^-2, and 1.6 × 10¹¹ cm^-2 . Three more devices were tested using 1.4 ♦ 10⁸ Helium ions/cm² at 1 GeV/n over a six minute exposure for a dose of 20 rad (water). Three additional devices were exposed to 1 GeV/n Fe fluence of 2.8 × 10⁵ ions/cm² for half a minute delivering a dose of 6 rad (water). Another three Extended InGaAs PD and GaAs TIA fibered devices were tested using Cesium-137 gamma rays of 662 keV for 15 krad (water). Pre- and post-radiation results were measured for (1) dark current vs. voltage for the InGaAs photodiodes, (2) responsivity (quantum efficiency) for the photodiodes, (3) optical return loss for the photodiodes, (4) TIA drive current, (5) bandwidth of the PIN + TIA, (6) conversion gain of the PIN-TIA, and (7) Bit Error Ratio (BER) of the PIN-TIA for 10.709 Gbps NRZ-ASK signal. All devices were found to be fully functional at normal operating conditions and at room temperature. All these efforts will advance the Technology Readiness Level (TRL) of these devices by year 2020.

A multimode interference (MMI) sensor was designed and experimentally demonstrated for simultaneous measurement of curvature and temperature. A typical fiber structure of single-mode fiber – multimode fiber – single-mode fiber (SMS), mounted in a long and thin carbon steel sheet, and then coated with polydimethylsiloxane (PDMS) was manufactured and tested in curvature and temperature. Bending laboratory results showed that the proffered sensor has a curvature sensitivity of -0.9835 dB/m^-1 over a range from 0 m^-1 to 1.3652 m^-1 , measurements were taken by keeping a constant temperature of 30°C. The laboratory temperature response was -119 pm/°C at a temperature range from 30°C to 60°C, showing an improvement in temperature response, temperature measurements were taken by keeping a constant bending of 0 m^-1 . The results show that PDMS coatings are a good way to improve multimode interferometer sensitivity during temperature measurement while keeping a good curvature measuring response, moreover the device shows a linear response within the curvature and temperature ranges. Another advantage of the PDMS coating is that it makes the sensor insensitive to refractive index changes, it gives the sensor robustness and protection against dust.

The heightened demand for non-mechanical approaches to beam redirection and steering has led to several electro-optical approaches. One with great potential integrates liquid crystal (LC) as a cladding layer to a planar waveguide for continuous two dimensional steering. The birefringence of LC is leveraged to tune the waveguide effective leading to refractive steering, while efficient coupling with a freespace beam is accomplished with a “tapered gap” prism coupler. The out-coupled beam can be steered by refraction in a continuous manner to follow a path or address random points with sub millisecond response times. This device architecture presents a challenge for modeling and simulation with a large parameter space. Experimental successes have motivated a custom MATLAB model that couples LC and waveguide physics. The model simulates the distortion of the nematic LC and uses the graded index profile at the cell boundary to solve the waveguide equation as a function of applied voltage. Raytracing methods are used to track the refraction of an input beam through regions of tunable waveguide index and predict the angular field of regard (FOR). Numerical simulations of the coupling region predict the coupling efficiency given the conditions of the input beam including arbitrary bandwidth. Comparison of coupling conditions and FOR measurements with empirical results allows us to rapidly prototype a device by optimizing parameters with fast algorithms that maximize the field of regard and throughput efficiency.

This study describes parametric modeling of near-infrared (NIR, 0.7-0.9 μm) and shortwave infrared (SWIR, 0.9-1.7 μm) absorbance spectra, which is for optimizing NIR-SWIR reflectance of dyed fabrics with respect to given illuminations and background environments. The parametric models are linear combinations of gaussian functions, which are for modeling dyes in fabric whose absorption spectra span the NIR/SWIR spectral range. In general, decomposition of an absorbance spectrum in terms of linear combinations of gaussain functions is not unique. This suggests investigatng what are optimal linear combinations of gaussian functions for modeling given spectra. Prototype modeling is applied to NIR/SWIR absorbing dyes, and their mixtures, in fabric samples, which consist of a cotton blend. The results of this study demonstrate parametric modeling using linear combinations of gaussian functions for simulating NIR/SWIR absorbance spectra, which are for variable dye and dye blend concentrations in fabrics.

Nowadays, the Shack-Hartmann aberrometer is one of the most widely used devices for measuring optical aberrations of the human eye due to the closed-loop automation features of this sensor. These aberrometers are used in fundus cameras to measure aberrations inherent to the human eye, which represent a deformation of the cornea that prevents the capture of eye images of high spatial resolution and can be compensated by adaptive optical systems. This article shows the validation of an experimental Shack-Hartmann aberrometer, which in the future will be used as the optimized adaptive optics arm of an eye fundus camera for the purpose of obtaining sharp images of the retina and its photoreceptors for the preventive diagnosis of anomalies that could generate partial or total loss of vision of the human being. The validation is done by a statistical analysis between the aberrations obtained from our experimental system and a commercial aberrometer. This analysis will be based on the most common aberrations of the human eye, e.g. myopia and astigmatism.

In the pulse laser ranging system based on time-of-flight measurement, since different targets have different reflection characteristics, the echo light intensity will affect the leading edge moment received by the range finder, which results in the deviation of the ranging result. In order to address this problem, this paper proposes a leading edge time correction model based on pulse width. The pulse width of the echo is positively correlated with the light intensity, so the pulse intensity can be used to characterize the light intensity and correct the leading edge time. According to Marius law, the leading edge moment acquisition experiments are carried out under different echo intensities produced by polarization state generator (PSG). It has been demonstrated that the presented model is consistent with experimental data. From the analysis and discussion, it is shown that the correction model can effectively correct the error caused by the echo light intensity of the pulsed laser ranging system, thus improving the accuracy of ranging.