This PDF file contains the front matter associated with SPIE Proceedings Volume 12091, including the Title Page, Copyright information, Table of Contents and Conference Committee list.

In this presentation, we will report our recent efforts in achieving high performance in Antimonides type-II superlattice (T2SL) based infrared photodetectors using the barrier infrared detector (BIRD) architecture. The high operating temperature (HOT) BIRD focal plane arrays (FPAs) offer the same high performance, uniformity, operability, manufacturability, and affordability advantages as InSb. However, mid-wavelength infrared (MWIR) HOT-BIRD FPAs can operate at significantly higher temperatures (>150K) than InSb FPAs (typically 80K). Moreover, while InSb has a fixed cutoff wavelength (~5.4 μm), the HOT-BIRD offers a continuous adjustable cutoff wavelength, ranging from ~4 μm to >15 μm, and is therefore also suitable for long wavelength infrared (LWIR) as well. The LWIR detectors based on the BIRD architecture has also demonstrated significant operating temperature advantages over those based on traditional p-n junction designs. Two 6U SmalSat missions CIRAS (Cubesat Infrared Atmospheric Sounder) and HyTI (Hyperspectral Thermal Imager) are based on JPL’s T2SL BIRD FPAs. Based on III-V compound semiconductors, the BIRD FPAs offer a breakthrough solution for the realization of low cost (high yield), high-performance FPAs with excellent uniformity and pixel-to-pixel operability. Furthermore, we will discuss the advantages of the utilization of all digital read out integrated circuits with HOT-BIRDs.

For the current strained layer superlattice (SLS) based FPAs mesa structures are used to define the pixels. For those SLS based FPAs with scaled pixel size making the mesa structures is challenging due to the need for deep etch, and then passivation process. One of the possible solutions to address this issue is to consider a planar structure and avoiding the mesa-isolation etching or complex surface treatment/ passivation process. In this work, the recent progress on planar SLS photodetector using ion-implantation for device isolation is presented. In this method of fabrication, ion implantation was applied from the top to bombardment the surface for device isolation, similar to mesa-isolation step in device fabrication. The devices are presented here are heterostructure SLS photodetector. The electrical and optical performance of the devices were characterized to give deeper view of the device performance.

HgCdTe material has been grown on GaAs substrates using Metal Organic Vapour Phase Epitaxy (MOVPE) and 64 x 64 arrays were subsequently manufactured. HgCdTe was grown on 12 wafers and 6 wafers continued through processing. Companion 320 x 256, 24 μm pitch arrays were also manufactured on the same wafer. These 320 x 256 arrays are hybridized to an existing imaging ROIC. Signal and noise data are collected as a function of bias to determine Gain vs Bias and operability of the companion detector arrays. The existing 320 x 256 ROIC was designed for astronomy applications and precludes measurements at bias values < ~ 10 V since the amplified signal from the detector saturates the well of the ROIC. Gain was measured for bias values up to ~ 10 V and extrapolated to determine gain at higher bias values. This ROIC also does not permit fast pulse measurements. An alternate ROIC has been designed for fast pulse measurements but will not be presented here. Based on the 320 x 256 array signal, noise, Gain vs Bias and morphology data all 6 processed wafers yielded 64 x 64 detector arrays that are available for hybridization to ROICs. 320 x 256 arrays had operability < 99.9% based on the signal and noise data. Response and noise histograms have mean and median values within 1% of each other. The noise histogram is near Gaussian in shape. APD arrays hybridized to fanout chips are in assembly and APD gain vs bias, noise and transient response measurements are being measured directly without going through a ROIC.

We have successfully tested simultaneously 2.4 Micron Wavelength, Extended InGaAs Photodiodes having diameters of 20, 30, 40, 50, 100, 150, 200, 250 and 290 Micron, coupled with a Single Mode Fiber using Hydrogen (H), Helium (He), and Iron (Fe) Ions which collectively make up over 90% of the Galactic Cosmic Rays (GCR). During irradiation, the devices were maintained at dry ice temperature, reverse biased at 100 mV, and their leakage current was continuously monitored in-situ during the run. After the exposure was completed, all nine devices were monitored for any change in their leakage current at 100 mV and room temperature for several weeks to monitor any annealing effects that may occur. Nine Photodiodes with the above varying diameters were radiated with 100, 250, 500 and 1000 MeV/n Hydrogen, Helium, and Iron Ions with a fluence of 10⁶, 10⁷ and 10⁸ ions/cm² at each energy level. Pre- and Post-radiation results were also measured for: (1) Leakage Current Vs. Voltage for the InGaAs Photodiodes; (2) Responsivity (Quantum Efficiency) in A/W for Photodiodes; and (3) Bandwidth of the Photodiodes. All devices were found to be fully functional at the normal operating conditions and at both dry ice and room temperature. We did not observe any post radiation annealing effect for leakage current at room temperature and 100 mV bias for any of the devices after several weeks of data logging.

The performance of optical and imaging systems may be limited considerably by losses due to reflection of signals off substrates and optical components. Nanoengineered optical layers offering tunable refractive index properties provide broadband and omnidirectional suppression of light reflection/scattering with increased optical transmission for enhanced detector and system performance. These nanostructured antireflection (AR) coatings custom designed for specific wavebands from the ultraviolet (UV) to infrared (IR) have many potential optical applications, particularly in maximizing light and IR radiation transmitted onto the surfaces of detectors to increase their sensitivity, for various NASA systems. Through fabrication of these AR nanostructures at various tilt angles of deposition, optimized AR coatings having high laser damage thresholds and reliable in extreme low temperature environments and under launch conditions may be realized. We have developed and advanced such AR nanostructures on GaSb substrates as well as GaSb-based detector devices for 8-14 µm LWIR applications. In this paper we review the latest findings and measurements in the development of these high-performance nanostructure-based AR coatings primarily for advanced LWIR band to NASA Earth Science sensing and imaging applications.

Microbolometers are the detectors most used in infrared imaging systems, these detectors have the disadvantage of being slow and require a bias voltage to operate, which increases the power requirements of the system. The current trend is to transition to low size, weight, and power (low SWaP) imaging systems. Seebeck nanoantennas are resonant elements made of two dissimilar thermoelectric materials tuned at a particular wavelength, when this wavelength is incident on the nanoantenna it induces a current that increases the temperature at the feed of the antenna generating a temperature difference that produces a Seebeck voltage. Due to the small size of the antenna and its low thermal mass Seebeck nanoantennas are considerably faster than traditional bolometers. Also, since the thermoelectric elements provide an output voltage no bias is needed for operation, reducing the power requirements of the whole imaging system. Previous work has reported the use of antennas traditionally used in the microwave region of the electromagnetic spectrum as Seebeck nanoantennas, these antennas are polarization dependent which is not usually desired in infrared imaging systems. In this work a multipolarized Seebeck nanoantenna is analyzed as a potential infrared pixel, their responsivity and detectivity are calculated from Multiphysics simulations for different pixel sizes.

A scalable, low cost, low power, and small footprint uncooled mid-wave infrared (MWIR) sensing technology capable of measuring thermal dynamics with high spatial resolution can be of great benefit to space and satellite applications such as remote sensing and earth observation. Conventional photodetectors designed to absorb MWIR band wavelengths have often been based on HgCdTe material and typically require cooling. However, through integration of bilayer graphene functioning as a high mobility channel with HgCdTe material in photodetectors, higher performance detection over the 2-5 μm MWIR band may be enabled and facilitated primarily by thus limiting recombination of photogenerated carriers in these detectors. This high performance MWIR band detector technology is being developed and tested for NASA Earth Science, defense, and commercial applications. Graphene bilayers on Si/SiO2 substrates are doped with boron using a spin-on dopant (SOD) process and then transferred onto HgCdTe substrates for enhanced mobility photodetection applications. Raman spectroscopy, X-ray photoelectron spectroscopy (XPS), and secondary-ion mass spectroscopy (SIMS) were utilized for analysis of dopant levels and structural properties of the graphene throughout various stages of the development process to characterize the p-doped graphene following doping and transfer. The enhanced performance and functional capabilities of the room-temperature operating graphene-based HgCdTe MWIR detectors and arrays are thereby demonstrated through modeling, material development and characterization, and device optimization.

The capabilities of neuromorphic (event) based sensors for atmospheric turbulence characterization and refractive index structure parameter ( C²_n ) sensing are investigated. The experimental setup used a system that consisted of a telescope with an attached neuromorphic camera that was imaging features of a corner of an installation on the roof of a building in 7 km distance. Synchronously with recording of the event stream from neuromorphic sensor the refractive index structure parameter was measured with a commercial scintillometer along the same propagation path. A processing technique was developed to compare the distribution-width of events generated by the edges of the imaged corner within a given time-span to the measured strength of turbulence from the scintillometer. Spatio-temporal analysis was applied to show the possibility to detect influence of wind flow in the of recorded event stream data.

Mobile mapping becomes a more and more important and interesting field of sensing technologies and their application scenarios. Various applications range from airborne sensing of specific environments and characteristics to ground-based applications such as multimodal 3-dimensional registration of environments in the infrastructure sector or for assistance systems. In the specific case of infrastructure systems, known fields of application range from the detection of the surface condition of roads to the digitization of entire railroad lines, including their clearance diagrams. From the technical point of view, it also combines a wide variety of sensory approaches for sensing relevant features. For example, known systems use both LiDAR and GNSS and image processing-based subsystems. This work summarizes the state-of-the-art mobile mapping technologies in the framework of road detection and digitization concerning the application of georeferenced condition monitoring. In the first part, the relevant historical development will be briefly reviewed and compared regarding technological progress furthermore, various sensing systems will be compared regarding their applications, applicability and limitations. The aim is to clearly identify shortcomings regarding the application case of road detection in the forestry sector and thus to lay the foundation for subsequent research and development work for multimodal sensing systems. It is also the starting point for upcoming work for a multimodal sensing system that is able to digitalize and characterize the structure of forestry trails. The data obtained in this way will later be used for a planning tool that will derive measures for the maintenance and repair these forest roads.

Rapid developments in infrared (IR) and electro-optical (EO) systems are crucial to further enhance the intelligence, surveillance, and reconnaissance (ISR) capabilities of platforms. The operational conditions of these platforms are getting harsher each day and new technologies must be adapted into these EO/IR systems swiftly to keep up with these challenges. While the performance requirements are increasing, the size, weight, and power (SWaP) constraints are becoming more stringent, especially in airborne platforms such as UAVs. Land systems and naval platforms don’t typically use EO/IR systems for the purpose of ISR, but regularly for situational awareness and self-defense. Airborne systems are where EO/IR systems are most used for ISR purposes. Especially with UAVs becoming cost effective and being deployed on longer missions EO/IR systems have become a vital part of UAVs. In both land and naval platforms these EO/IR systems are mostly placed upon a pan-tilt stage; however, on airborne platforms, the EO/IR systems are packaged in a tight gimbal where SWaP is a real issue. Advancements in infrared detector technology such as smaller detector pitch and high operating temperature (HOT) detectors are paving way for compact imagers with high resolution. Folding the optical path using mirrors in continuous zoom systems is a way to reduce the size of the objective which often takes a lot of space. Novel actuation methods have been gradually utilized in these systems. Incorporating all these new technologies and designs is a good way to meet the emerging challenges of EO/IR systems for the purpose of ISR.

THz testing has been recently proposed to identify altered or damaged ICs. This method is based on the fact that a modern field-effect transistor (FET) with a sufficiently short channel can serve as a terahertz detector. The response can be recorded while changing the THz radiation parameters and location and compared to a trusted one for classification. We measured the THz response of original and damaged ICs for classification using different Transfer Learning models as a method of deep learning. We have achieved the highest classification accuracy of 98%.

Calculations are presented of vibrational absorption spectra for isolated molecules of some common pesticides using density function theory (DFT). This study further demonstrates using DFT for characterizing IR-spectral features of substances within the environment. DFT calculated absorption spectra of isolated molecules represent quantitative estimates that can be correlated with additional information obtained from laboratory measurements. The DFT software GAUSSIAN was used for calculating the infrared (IR) spectra presented here. DFT calculated spectra can be used to construct templates, which are for spectral-feature comparison, and thus detection of spectral-signature features associated with target materials.

This study describes a Kramers-Kronig analysis of diffuse reflectance from NIR/SWIR-absorbing dyes on cotton fabric substrates for estimating dielectric response functions. The calculated response functions do not directly capture the dielectric functions of the dyes, which are material properties, but rather provide estimates of the dielectric response characteristics – including the dye and substrate interactions. Since the Kramers-Kronig analysis is applied to diffuse reflectance and not to specular reflectance from uniform bulk material surfaces, it cannot provide an exact determination of the material permittivity functions. However, the calculated response functions can support the construction of approximate effective medium models capable of estimating reflectance from dyed fabrics. This study investigates the construction of such models using the calculated dielectric response functions. Additionally, a sensitivity analysis explores the impact of the Kramers-Kronig integration range incompleteness by testing lower/upper wavelength smoothing and extrapolation techniques.

Surface inspection in industrial automated processes is very often challenging. Especially the detection of transparent liquid materials such as water represent a major challenge for standard imaging systems. One approach to overcome the limitation of these imaging systems lies in the exploitation of the polarization effect. This effect surely can only be applied if the contaminants have polarizing features but can help to use invisible characteristics of light for quality inspection tasks. In this work investigations on surfaces which are contaminated with water will be presented. Therefore, an imaging system using an RGB dome light illumination was set up in combination with a four-channel polarizing camera. The dome light, which is equipped with three different LED wavelengths, will be mixed so that the illumination which hits the sample is completely unpolarized. So, any effect on the surface which leads to a polarizing effect can be observed. The system delivers a four-channel image with different polarization angles that have to be processed. Therefore, an algorithm realizes a demosaicing which separates the four different polarized pixels into individual images. Based on this, the stokes equation which allows the calculation of the degree of polarization and the angle of polarization has to be processed for the image presentation. To achieve a better visualization of the degree of polarization an HSV-transformation based on the polarization parameters was also realized.

In this paper, a new method for determining the curvature of the drill's rake surface is developed. The new method is based on the identified functional relationships between the focus area in the image and the shape of drill’s rake surface. The revealed relationships allow for the determination of the curvature of the front surface of the drill, which can be used to determine the geometric parameters of the chip flute. The method is based on the analysis of images obtained in the process of measurement by a camera in reflected light. To implement the developed method, the drill was fixed in a collet chuck on a NC measuring machine, the camera is pointed at the front surface area, and a series of images with different focal lengths was taken. After processing the images obtained in reflected light, the shape of the rake surface of the drill in the radial section was determined. The accuracy of the proposed method is proved by comparison with the data obtained from the measuring machine

Since the operating conditions of nanolayer systems are usually stochastic, modeling the processes occurring in them requires the use of probabilistic methods. The application of the method for calculating percolation by nodes and bonds for solving the problem of stochastic loading of nanolayer structures is facilitated in comparison with those usually used in various physical and technical problems. In this case the impact is not carried out at the boundary of the two-dimensional region of the nanomaterial, with the finding of stresses and strains inside the layer. Instead, stresses and strains are determined in the very surface layer of the material under the influence of an external load. Here we show that with an increase in the number of nodes and bonds in the system, the development of a crack is slow down and that the use of layered systems with a superlattice crystal structure, with minimized internal residual stresses, can provide increased crack resistance.

Fatigue microcracks, caused by mechanical or thermal impacts, are formed during periodic stretching and compression of the upper layers of nanostructured materials. Then, the microcracks grow further and merge, leading to the cleavage of the material fragment and its subsequent destruction. In this work, we have performed calculations and transfer showing that it is necessary to structure nanomaterials in such a way as to form residual compressive stresses, which can serve as a barrier to crack propagation, in them. Here we also show that shear stresses are largely responsible for initiating the microcrack formation in nanostructured materials.

We have developed a low SWaP-C enabling Metamaterial Spectrometer (MMS) device for hyperspectral imaging in the MWIR. Our chip-based MMS device couples a Distributed Bragg Stack filter with a sub-wavelength dielectric resonator metasurface. The former gives the device a narrow passband, while the latter can be pixelated into an arbitrary number of parallel spectral channels, each with an independently engineerable center wavelength and bandwidth to create a hyperspectral or multispectral filter. The all-dielectric structure provides low optical loss vs. metallic plasmonic resonators. The metasurface resonators are engineered to accept light across a wide angle-of-incidence cone while being integrated directly into existing focal plane array (FPA) detectors. A wide acceptance cone of light eliminates the need for collimating optics, thereby reducing the SWaP requirements of the MMS relative to competing technologies. The MMS can be fabricated on a wafer scale using standard nanofabrication techniques, which are cost-effective for highvolume manufacturing. Although our initial prototype has been implemented in the MWIR, the generalized MMS structure can be implemented in other infrared spectral ranges by via appropriate choices of materials and rescaling of dimensions. Potential commercial applications of the hyperspectral MMS include environmental monitoring, medical diagnostics, antiterrorism, forensics, and food safety.