This PDF file contains the front matter associated with SPIE Proceedings Volume 10639 including the Title Page, Copyright information, Table of Contents, and Conference Committee listing.

Recently discovered photon sources based on 2D materials are much more practical compared to their earlier counterparts due to high emission rate, robust performance in a range of environmental conditions and ease of photonic integration. It is expected that this platform will make a substantial contribution to a range of quantum optical applications, including quantum communication, computing and sensing.

Layered materials have recently emerged as a promising class of optoelectronics material with high quantum efficiency of photo-emission, absorption and nonlinear optical properties. With significant progress in understanding the material science of these atomically thin materials, it is an opportune time to integrate these materials with existing optoelectronic platform to realize the full potential of the 2D materials. Integrating 2D material with nano-resonator could efficiently enhance the light-matter interaction and develop novel optoelectronics devices. Cavity-enhanced 2D material electro-optics modulation, nano-laser, and second order nonlinear devices has been demonstrated. In this paper, we report our recent progress on the cavity-integrated TMDC monolayer platform, including novel cavities for 2D material photonics and cavity nonlinear optics.

The implementation of quantum networks and distributive quantum information processing relies on interaction between stationary matter qubits and flying photons^1-6. The spin of a single electron or hole confined in a charged quantum dot is considered as a promising matter qubit as it possesses microsecond coherence time^7,8 and allows picosecond timescale control using optical pulses^9-12. The quantum dot spin can also interact with a photon by controlling the optical response of a strongly coupled cavity^13-15. So far most experimental demonstrations of the cavity spectrum control have used neutral quantum dots^16,17. Spin-dependent cavity spectrum has not been reported yet. Here, we report an experimental realization of a spin-photon transistor using a strongly coupled quantum dot and cavity system. We show large modulation of the cavity reflectivity by manipulating the spin states of the quantum dot. The spin-photon transistor is crucial for realizing a quantum logic gate or generating hybrid entanglement between a quantum dot spin and a photon^18-21. Our results represent an important step towards semiconductor based quantum logic devices and on-chip quantum networks.

Plasmonic resonant properties of nanoparticles, nanowires and nanotubes forming heterodimensional junctions with twodimensional electron gas (2DEG) enable local resonant coupling and could be used for subwavelength imaging. The resonant plasmon frequency of a nanoparticle is tunable by varying the bias of the gate capacitively coupled to the nanoparticles. Our analyses of the plasmonic properties of nanoparticles accounting for the boundary scattering and for the carrier fluid velocity shows that the plasma oscillations in Si, GaN, and InGaAs and nanoparticles could achieve high quality factors. Single embedded nanoparticles or arrays of such nanoparticles placed into the perforated asymmetrical 2DEG or/and 2DHG structures or superlattices could be used for detection, mixing, or frequency multiplication of sub- THz, THz or IR radiation. The embedded nanoparticle arrays could be also used as active elements of THz emitters and as sub-THz, THz, or IR sensitive photodetector layers for pixelless THz to visible converters.

Pixel size in cameras and other refractive imaging devices is typically limited by the free-space diffraction. However, a vast majority of semiconductor-based detectors are based on materials with substantially high refractive index. We demonstrate that diffractive optics can be used to take advantage of this high refractive index to reduce effective pixel size of the sensors below free-space diffraction limit. At the same time, diffractive systems encode both amplitude and phase information about the incoming beam into multiple pixels, offering the platform for noise-tolerant imaging with dynamical refocusing. We explore the opportunities opened by high index diffractive optics to reduce sensor size and increase signalto- noise ratio of imaging structures.

Subwavelength imaging has recently seen increased interest in multiple fields. There are various applications and distinct contexts for performing subwavelength imaging. The technological ways to proceed as well as the benefits obtained are as various as the applications foreseen. To benefit from subwavelength imaging a way around standard imaging procedure is often required.

INO is also involved in this activity mainly for the infrared and the THz wavebands. In the infrared band a detector with 17 um pixel pitch, larger than the pixel, was used in conjunction with a microscanning device to oversample the image at a pitch much smaller than the wavelength. In this case the pixel size is in the order of the wavelength but the sampling is at subwavelength level. In the THz band a 35 um pixel pitch is used at wavelength ranging from 70 um to 1,063 mm to perform imaging through various objects. In this case, the pixel itself is smaller than the wavelength.

Subwavelength imaging is not without its challenges, though. For instance, while the use of ultra-fast optics provides better definition, their design becomes more challenging as the models used are at their very limits. Questions about information content of images can be raised as well. New research avenues are being investigated to help address the challenges of subwavelength imaging with the goal of achieving higher imaging system performance. This paper discusses aspects to be considered, review some results obtained and identify some of the key issues to be further addressed.

Hyperbolic metamaterials acting as spatial filters, passing incident evanescent waves and blocking incident propagating waves, can be produced for ultraviolet wavelengths by a stack of alternating metal/dielectric films. However, real fabricated devices have disordered layer surfaces due to imperfect material deposition. Here, we investigate the effect of realistic surface roughness on the spatial filtering properties of such devices. The findings have implications in subdiffraction imaging and photolithography.

The Materials Genome Initiative (MGI) is a multi-agency partnership that seeks to accelerate the pace of materials development across the Materials Development Continuum. Through use of a computationally-led and data-driven approach, MGI promotes the rapid discovery and deployment of advanced materials that will ensure sustained American leadership in sectors including energy, electronics, and photonics. The goals of the MGI include 1) leading a culture shift in materials research through use of an iterative feedback-loop approach, 2) integrating experiment, computation, and theory throughout the materials research community, 3) making digital data accessible and useful to the larger community, and 4) creating a world-class materials science and engineering workforce. The Designing Materials to Revolutionize and Engineer our Future (DMREF) program at the National Science Foundation (NSF) partners with a number of other federal funding agencies to promote these objectives. DMREF includes participation from ten divisions in three directorates at the NSF to address fundamental materials discovery and development. This program currently funds about one hundred projects that cover the full spectrum of materials research. Among these are a number of projects that focus on electronic and photonic materials and devices in both the organic and inorganic realms. Graphenebased origami and kirigami metamaterials are among those being developed thought this methodology. The principles of the MGI are described and examples from specific DMREF projects are provided.

As we are at the verge of entering the era of Internet-of-Things (IoT), there is a clear need to produce continuous power supply to the huge amount of electronic devices that must be wirelessly interconnected and operate uninterruptedly. At the same time, new mechanical constrains arise from the fact that these devices should be ubiquitous, which leads to the need of lightweight and mechanical compliance to any shape or surface. As an important renewable energy source, a mechanically adaptable thermoelectric generator (TEG) can make use of the usually wasted thermal differences between ambient and technology-users to power-up such systems. With this idea in mind, we have developed a simple approach to fabricate TEGs, based on commonly available substrates (paper or polymers) and assisted through simple folding and cutting techniques (born from origami and kirigami) to form strategic structures (serpentine, helical, spiral, etc.) with the mechanical advantage of foldability and over 100% demonstrated stretchability. The use of these methods and structures allows the mechanical reconfigurability of the devices to, for example, increase the temperature difference in a TEG, thus its power, or allow a more efficient use of area and therefore increase the power density. We will discuss the strategies to effectively integrate folding and cutting techniques with common materials and the basic TEG configuration, as well as demonstrate the devices’ implementation and characterization. Finally, we believe our simple integration approach offers an interesting and versatile methodology, which can be easily extrapolated to new materials and technologies for a greater variety of applications.

After many years of directed investment, integrated photonics technologies have begun to enable sophisticated solutions for fiber-optic communications. The increasing maturity and availability of photonic integrated circuits will ultimately enable a variety of revolutionary chip-scale applications including LIDAR, chemical and biological sensing, precision metrology, quantum information processing, and free-space laser communications. However, providing impact in applications beyond datacom has proved challenging because the toolset developed for digital communications often fails to meet the broader needs of new applications. This talk describes DARPA efforts to improve passive and active integrated photonics components, along with relevant programs that are driving technology innovation. The Modular Optical Aperture Building Blocks (MOABB) program is an effort to develop optical LIDAR using planar photonics components in the place of bulky optics and slow, costly mechanical beam steering elements. MOABB creates an optical phased array which combines coherent light from individual emitter elements placed on a wavelength-scale pitch. Electrically-addressed phase modulators control directionality for transmit and receive functions. Key MOABB device challenges include the dense integration of small phase modulators, high-power tunable lasers, and high-speed drive electronics. The Direct On-chip Digital Optical Synthesizer (DODOS) program seeks to develop a chip-scale optical frequency synthesizer using a self-referenced optical frequency comb to precisely control the output of a narrowband tunable laser. DODOS has driven the development of high Q microresonators, chip-scale modelocked lasers, efficient frequency doublers, and wideband passive elements that operate with low loss across an octave of spectrum.

We investigate mechanisms by which interaction of light and matter may be affected by electrons, and show how this can lead to optoelectronic devices with superior properties. In particular, confined cloud of electron gas allows sculpting a wave function that affects both emission and absorption of radiation, while its collective, plasmonic, excitation may be used for optical wave guiding, coupling and radiation. Such processes require much less energy and are much faster than classical kinetic energy-based charge transport in traditional electronics. Here we present thin-film photodetectors in which 2D electron and hole charges allow operation in hundreds of GHz, without applied bias, requiring a fraction of microwatt of optical power. The 2D channel can also be structured to provide the momentum change that is required for coupling to excitation at THz range. The confined charge is then used as a plate of (an unconventional) capacitor which changes states by a factor of >1000, in tens of fs, requiring atto-joules of energy which is also switchable by light. This opto-plasmonic capacitor finds application in threshold logic based neuromorphic systems. These thin-film devices are produced in bottom-up core-shell nanowire (CSNW) technology, resulting in resonant optical cavities whose properties are controlled by 2D and 1D charge plasma, with orders of magnitude increase in absorption and emission of light that leads to lasing at room temperature even without vertical structure. Since CSNWs can be grown on Si, they can be good candidate platforms for Photonic Integrated Circuits (PIC) and Silicon Photonics.

Micro and nanoscale holes on the surfaces of indirect band gap semiconductors such as silicon can enable perpendicular light bending and trapping of photons to enhance the light material interactions and absorption by orders of magnitude. The ‘bending’ of a vertically oriented light beam at nearly 90 degrees can be visualized as radial waves generated by a pebble dropped into a calm pool of water. Such bending and photon trapping result in an increased optical absorption path enabling very high light absorption coefficients. This observation led to the design of silicon photodetectors with high broadband efficiency above 50% and record ultrafast response contributing to more than 40 billion bits of data per second (Gb/s) communication speed.

Present infrared (IR) detection techniques are limited due to the absence of spectroscopic or “color” detection/imaging abilities. At present all cooled and uncooled MWIR and LWIR detectors are being “bucket” detectors generate integrated spectral images in the binary color format (choices of any two pseudo colors). To date very little research work has been performed on frequency selective detection. On the other hand if we see natural world we find many animals that can see over multiple spectral bands in the visible as well as in the infrared domain. Mantis shrimp eye is an example of a complex eye which is comprised of an elegant 12 channel spectrum sampler that spans the range 300-750 nm, with spectral bandwidth of around 40 nm. These are among the sharpest spectral sensitivities in the animal kingdom. The key aspect of their eye is “biological light funnel” apparatus which collect light over a wide angle with near perfect efficiency. Another biological masterpiece is pit vipers that have heat-sensitive membranes that can detect the difference in temperature between a moving prey—such as a running mouse—and its surroundings on the scale of milli Kelvins. Their infrared eye (“the pit”) has unique abilities to scatter visible light away and transmit only a band of infrared light which reduces background noise substantially. The grand challenge: Can we create an artificial eye/imaging system which has spectral resolving power like Mantis shrimp but viper like detection ability in the infrared domain? The talk will focus on the multi-spectral sensing/imaging that will provide unique intelligence in terms of spectrally resolved IR signature and/or “color” IR images. The novel printing/imprinting techniques enable development of large area, low cost IR detectors which can be mounted on various platforms efficiently with low SWaP requirements.

Efficient conversion of long-wavelength light into direct current represents a great potential for photodetection, photocatalyst, and photovoltaics, with a variety of applications in sensing, security, defense, and emissive infrared energy harvesting. We propose here a new type of plasmo-electronic nanodevice, engineered as the hyperbolic metamaterial (HMM), to efficiently trap and nonlinearly rectify the incoming infrared radiation. These HMM-based nanodevices are constituted by the periodic, dissimilar metal-insulator-metal (MIM) heterojunctions, whose homogenized material properties enable the perfect absorption of infrared radiation and the localization of optical fields. The nonlinear optical rectification driven by the multiphoton-assisted tunneling in the MIM heterojunctions can efficiently convert the infrared radiation into the DC electricity (photocurrent). Most interestingly, the wideband or frequency-selective photon-to-electron conversion can be controlled via the design of HMM nanostructures. Our theoretical and numerical results demonstrate that the zero-bias responsivity of the HMM-based nanodevices can be up to ~100 mA/W in the mid-infrared regime.

We report the generation of spin controlled OAM of light in harmonic generations by using ultrathin photonic metasurfaces. The spin manipulation of OAM mode of harmonic waves is experimentally verified by using second harmonic generation (SHG) from gold meta-atom with three-fold rotational symmetry. By introducing nonlinear phase singularity into the metasurface devices, we successfully generate and measure the topological charges of spin-controlled OAM mode of SHG through an on-chip metasurface interferometer. The nonlinear photonic metasurface proposed in this work not only opens new avenues for manipulating the OAM of nonlinear optical signals, but also benefits the understanding of the nonlinear spin-orbit interaction of light in nanoscale devices.

First, we present the realization of the ultra-high-definition dynamic 3D holographic display. Using wavefront shaping techniques with highly scattering holo-graphic diffusers, we generate dynamic 3D holographic images with significantly increased viewing angle and image size. Volume speckle fields, generated by holographic diffusers, are actively controlled using a wavefront shaping technique; as a result, the viewing angle and the image size are enhanced by a factor of 2,600 compared to the case of using the DM only. We demonstrate the dynamic display of micrometer-size optical foci in a volume of 8 mm x 8 mm x 20 mm, which far exceeds the capability of existing technology. In addition, we also present a method for direct holography, which enables measurements of an incident field without additional reference beams or assumptions. Inspired from the Siegert equation that connects intensity correlation with field correlations in the time domain, we present the new concept to retrieve the incident field from a speckle intensity pattern in the spatial domain. By measuring a speckle intensity image that is generated when a light field of interest passes through a calibrated turbid layer, field information of an arbitrary optical field can be directly reconstructed. As a proof-of-concept, we demonstrate a compact holographic image sensor, composed of a diffuser and a 2-D image sensor, and present both 2-D and 3-D optical field imaging. [1] Hyeonseung Yu et al., Nature Photonics, 11 :186 (2017) [2] Kyeoreh Lee et al., Nature Communications, 7:13359 (2016)

This paper presents a review of the controlled growth of transition metal dichalcogenide (TMD) heterostructures, and the elucidation of the role of underlying two dimensional (2D) materials on temporal degradation of transition metal dichalcogenides (TMDs). Chemical vapor deposition (CVD)-growth is carried out to achieve localized, patterned, single crystalline or polycrystalline monolayers of TMDs, including MoS₂, WS₂, WSe₂ and MoSe₂, as well as their heterostructures. The localized growth of TMDs has an important implication for nonlinear optics applications. Extensive material characterization is performed to illuminate the role of dissimilar 2D substrates in the prevention of interior defects in TMDs. This characterization provides a detailed observation of the oxidation rates and behaviors of TMDs, which corroborate the role of underlying 2D layers in the prevention of in-air oxidation in TMDs. The epitaxial growth is demonstrated to create TMDs on hBN and graphene, as well as vertical/lateral heterostructures of TMDs, uniquely forming in-phase 2D heterostructures.

The integration of graphene and 2D materials into device technologies requires a detailed understanding of how intrinsic and extrinsic forces impact their properties, as well as the development of engineering strategies to vary their properties for a specific response. In this paper we describe and review our efforts for hybridizing graphene in different ways so as to modify or enhance a range of properties. This hybridization comes in the form of chemical or electronic modification for use in applications ranging from chem/bio sensors to nanoelectronics. We discuss results on exploiting chemistry and defects in graphene for chemical vapor sensing, on hybridizing graphene with fluorine atoms for potential use in nanoelectronics, and on electronically hybridizing graphene in multilayer stacks that give rise to new optical and surface properties.

The understanding of two-dimensional (2D) materials has grown tremendously, especially for isolated monolayers. Recently, complex structures formed by stacking 2D materials have attracted considerable attention. This is in part due to the fact that the properties of monolayers are known to be influenced by their surroundings. Consequently, monolayer properties are predicted to be affected by “heterostructuring”. A study involving high-charge-carrier-density effects and dynamics is presented here for monolayers of WSe2 on different substrates and heterostructures comprised of 2D h-BN and WSe2. The influence of h-BN as well as the bilayer stacking order on the spectral and dynamical properties of WSe2- monolayer emission is discussed for the low-density regime and evidenced for high-density effects such as exciton-exciton annihilation and the Mott transition.

Atomically thin two-dimensional (2D) semiconductors boast numerous intriguing enhanced material properties for various potential electronic device applications. For optoelectronic devices, such as photodetectors and photovoltaics, an efficient light harvesting is highly demanded, and the relatively low absolute optical absorption of 2D semiconductors can, therefore, limit associated device performances, including photodetector responsivity and solar cell power conversion efficiency. Recently, the sensitization by quantum dots (QDs) has shown promises for improving the optical absorption in 2D semiconductors. In this talk, I will highlight our recent efforts towards utilizing QD sensitization for improving the photo-response of 2D semiconductor field-effect transistor (FET) photodetectors. The first example demonstrates a 500% enhancement in photocurrent response by the application of energy transfer from CdSe/ZnS core/shell QDs in 2D SnS2, a model 2D system with indirect band gap nature. Also detailed is the case of 2D MoS2, where we show that the light-intensity-dependent photo-response characterized by scanning photocurrent microscopy (SPCM) can distinguish two fundamental modes of interfacial interaction between QDs and 2D materials, namely energy and charge transfers, which are extremely difficult to distinguish under typically optical interrogation methods. I will try to discuss the potential implication of these two modes towards the optoelectronic application of QD-2D hybrid materials.

This paper presents a review of membrane-mimetic two dimensional (2D) nanomaterials assembled from sequencedefined, diblock-like peptoids through an evaporation-induced crystallization method. Similar to those associated with cell membranes, these peptoid-based nanomembranes exhibit thicknesses in the 3.5 - 5.6 nm range, spontaneous assembly at interfaces, thickness variations in response to changes in Na+ concentrations, and the ability to self-repair. Moreover, they are highly stable, free-standing, and atomically ordered. Both experimental and simulations studies showed that these nanomembranes were formed through an anisotropic formation process. We further demonstrated the incorporation and patterning of a broad range of functional groups within peptoid membranes through large side-chain diversity and/or co-crystallization approaches. By tuning the peptoid hydrophobic domains which determine the stability of nanomembranes, we demonstrated the assembly of singlewalled crystalline nanotubes through folding peptoid-based 2D nanomaterials. Given peptoids are biocompatible and easy to synthesize, we anticipate this new class of peptoid-based 2D nanomaterials will provide a robust platform for development of biomimetic materials tailored to specific applications.

The U.S. Department of Energy funds a large portfolio of fossil energy R&D projects aimed at transformational improvements in the cost and environmental performance of coal-based power generation while maintaining high reliability standards. The National Energy Technology Laboratory (NETL) manages DOE’s Crosscutting Research Program, which leverages on-going trends in disruptive technology to achieve breakthroughs in sensors and controls. Examples include: advanced manufacturing of embedded sensors with energy harvesting capability; wireless signal transmission and blockchain infrastructure; and the application of data analytics and machine learning to processing distributed sensor signals to create actionable control interfaces. The fossil energy application space requires the development of sensors capable of monitoring key operational parameters (temperature, pressure, and gas compositions) while operating in harsh environments; analytical sensors capable of on-line, real-time evaluation and measurement to support condition-based monitoring. Controls development centers around self-organizing information networks, algorithms for component lifetime assessment and plant-level economics, and distributed intelligence for process control and decision making. All of this must be accomplished while hardening fossil energy assets.

An overview of DOE’s Fossil Energy R&D Program with an emphasis on Sensors and Controls will be presented including discussion of technologies and applications being pursued and their status.

Fossil fuel combustion processes generate CO₂, a greenhouse gas of considerable concern. To reduce this emission, the National Energy Technology Laboratory (NETL) is evaluating alternative combustion approaches, including chemical looping combustion (CLC). This technique generates relatively pure CO₂, suitable for subsequent capture and storage. CLC uses oxygen-carrier particles (OCPs) such as iron oxides, copper oxides, calcium sulfates, etc. to provide oxygen for the combustion process. Optimization of the overall combustion process requires knowledge of the oxidation state (e.g., content of Fe₂O₃ vs. Fe₃O₄) of the OCPs during the different stages of the CLC process. Unfortunately, the ability to make on-line measurements of the oxidation state of OCPs in harsh environments is lacking and new sensors need to be developed.

We are evaluating non-contact, stand-off Raman spectroscopy to determine the relative concentrations of the oxidized and reduced forms of OCPs at temperatures between 800 °C and 1000 °C, and pressures of about 10 atm. Using cw and pulsed Raman spectroscopy, in combination with a pressurized high-temperature sample chamber, we have optimized the operating parameters such as laser wavelength, laser intensity, collection optic design, focal spot size, etc. and measured Raman spectra of various OCP materials at high temperatures. To extract from the Raman spectra relevant information such as the concentration ratio of a material in different oxidation states, the measured data needs to be processed, and statistical modeling and multivariate calibration need to be performed.

This paper presents a novel fiber optic ultrasonic sensing system to measure high temperature in the air. Traveling velocity of sound in a medium is proportional to medium’s temperature. The fiber optic ultrasonic sensing system was applied to measure the change of sound velocity. A fiber optic ultrasonic generator and a Fabry-Perot fiber sensor were used as the signal generator and receiver, respectively. A carbon black- Polydimethylsiloxane (PDMS) material was utilized as the photoacoustic material for the fiber optic ultrasonic generator. A water cooling system was applied to cool down the photoacoustic material. A test was performed at lab furnace environment (up to 700 ℃). The sensing system survived 700℃. It successfully detect the ultrasonic signal and got the temperature measurements. The test results agreed with the reference sensor data. The paper validated the high temperature measurement capability of the novel fiber optic ultrasonic sensing system. The fiber optic ultrasonic sensing system could have broad applications. One example is that it could serve as acoustic pyrometers for 3D temperature distribution reconstruction in an industrial combustion facility

In this work, a low-cost multipoint fiber optic sensor system for real-time monitoring of the temperature distribution on transformer cores was demonstrated. The temperature sensors are based on multi-mode random air hole fibers infiltrated with CdSe/ZnS quantum dots. Quantum dots resided in multi-mode random-hole core regions can be optically excited by guided UV light with extremely high quantum efficiency. The photoluminescence intensity dependence on the ambient temperatures were used to gauge the local operational temperature of transformer under strong magnetic fields. Multiplepoint temperature sensing systems were developed by bundling quantum dots infiltrated random air hole fibers together. Using a low-cost UV diode laser as a light source and a CCD camera as detector, hundreds of fiber sensors can be interrogated at low cost. This multi-point fiber sensor system, which is free from electromagnetic interference, was used to monitor temperature fluctuation of transformer from the room temperature up to 96°C with better than 1°C accuracy. The proposed fiber optic sensing scheme could overcome the shortcomings of traditional electric sensors and provide a versatile and low-cost approach to map the temperature distribution of electric power systems such as transformers operated in strong electromagnetic fields.

For 18 years NASA Earth Science Technology Office(ESTO) has been investing in remote sensing related technologies. During this period ESTO has invested in more then 900 tasks. These tasks are managed under multiple programs, which cover the whole spectrum of technologies from component to full up satellite in space and software. Many of these technologies have been successfully infused into space missions like Aquarius, SMAP, CYGNSS, SWOT, TEMPO and others. Researchers are demonstrating remote sensing instruments with various improved capabilities such as incorporating innovative spectrometers, or a single chip with spectral imaging capabilities. Recent technological developments in novel sensor materials, including those for hyperspectral imaging such as strained superlattice and barrier architectures, promise significant improvements in performance. Various read-out circuit architectures are improving functionality for higher-performance focal plane arrays, including incorporating intelligence into focal planes. Adding intelligence into sensors will lead to efficient utilization of limited onboard resources like power, and data rate. ESTO is actively investing in sensor technologies, instrument concepts, information technology and data processing algorithms for both active and passive remote sensing space applications. Recent investments have been for Sustainable Land Imaging(SLI-T), Inspace validation of technology (InVEST) and Instrument Incubator Program (IIP). This presentation will focus on remote sensing techniques and related technology investments by NASA/ESTO.

This presentation summarizes the advances made in the last 50 years in understanding, modeling, and mapping terrestrial vegetation as reported in the new book on “Hyperspectral Remote Sensing of Vegetation” (Publisher:Taylor and Francis inc.) and well as some very recent research. The advent of spaceborne hyperspectral sensors or imaging spectroscopy (e.g., NASA’s Hyperion, ESA’s PROBA, and upcoming Italy’s ASI’s Prisma, Germany’s DLR’s EnMAP, Japanese HIUSI, NASA’s HyspIRI) as well as the advances made in processing when handling large volumes of hyperspectral data have generated tremendous interest in advancing the hyperspectral applications’ knowledge base to large areas. Advances made in using hyperspectral data, relative to broadband data, include: (a) significantly improved characterization and modeling of a wide array of biophysical and biochemical properties of vegetation, (b) ability to discriminate plant species and vegetation types with high degree of accuracy, (c) reducing uncertainties in determining net primary productivity or carbon assessments from terrestrial vegetation, (d) improved crop productivity and water productivity models, (e) ability to assess stress resulting from causes such as management practices, pests and disease, water deficit or water excess, and (f) establishing more sensitive wavebands and indices to study vegetation characteristics. The presentation will discuss topics such as: (1) hyperspectral sensors and their characteristics, (2) methods of overcoming the Hughes phenomenon, (3) characterizing biophysical and biochemical properties, (4) advances made in using hyperspectral data in modeling evapotranspiration or actual water use by plants, (5) study of phenology, light use efficiency, and gross primary productivity, (5) improved accuracies in species identification and land cover classifications, and (6) applications in precision farming.

The Mako airborne longwave-infrared hyperspectral sensor is a whiskbroom imager operating in the 7.6-13.2 μm region with 44-nm spectral sampling and <30 mK noise-equivalent differential temperature (NEDT). It has undergone progressive development since its inaugural flights in 2010 and is capable of acquiring 112° swaths with an areal rate of 33 km² min^-1 at 2-m ground sampling distance. The sensor performance envelope allows for a number of operational modes that can be deployed against a variety of acquisition scenarios. Its suitability for environmental remote sensing applications is illustrated with reference to a number of representative case studies drawn from several years of airborne collections within the Los Angeles Basin and beyond.

With world projections of global population running to 9.5-10 billion by mid-century, it has becoming apparent that increasing food production will soon become an existential problem. However, the world has been here before. In the mid 1950’s parts of the developing world, especially in Mexico and India were facing national food crises. This previous situation helped spark a series of innovations that collectively became known as the “Green Revolution.” Recent advances in sensor technology, computer processing power, and algorithmic development have ushered in a new era of data-driven, precision farming. It is now possible to obtain precise measurements of biological phenomena on very large spatial and temporal scales. This development is part of a continuum of advances that have ushered in “Green Revolution 2.0” with Digital Farming technologies becoming the tip of the spear. In this paper we review the timeline and development of both biological and sensor technologies that are just now beginning to converge, with special emphasis on hyperspectral instrumentation. We address some very recent developments in the field and speculate about the potential of future advances to solve the pressing issue of adequate global food production.

Hyperspectral Imaging has been accepted for ocean color measurements from both airborne platforms and space-based instruments but has yet to be implemented with the desired ground resolution, coverage, revisit rate, and Signal to Noise Ratio (SNR) for coastal observations of biological processes. The low albedo and high levels of atmospheric scattering drives the need for 1000:1 SNR ocean color data, while harmful algal blooms or post-extreme weather events require daily revisit rates. To achieve higher SNR, Low-Earth Orbit (LEO) sensors must make the trade-off of aperture size and spatial resolution versus spacecraft size and complexity. Airborne missions can achieve the high SNR and spatial resolution needed but lack in coverage and revisit rates. Recent flights of the NASA ER-2 and stratospheric solar planes have suggested an opportunity for regional coastal hyperspectral imaging with multi-week observations, rapid revisit times, and low frame rates for high SNR. Stratospheric platforms, also known as High-Altitude Pseudo Satellites (HAPS), can fill this gap but have limited payload size, weight, and power (SWaP.) We present an example payload that fits within these limitations, the Compact Hyperspectral Advanced Imager (CHAI) for ocean color measurements. A solar plane HAPS UAV platform with a CHAI payload is compared against the baseline NASA HySPIRI LEO mission and the NASA AVIRIS-NG airborne system. Hyperspectral imaging is only one of the technologies needed for better understanding of the coastal environment. Other low SWaP coastal imaging payloads are discussed for applications including Solar Induced Fluorescence (SIF), Evapotranspiration (ET), and Methane Gas Imaging. For Earth Science applications such as coastal remote sensing, a HAPS platform with a suite of small sensors may be the optimal system for regional studies.

Harris is currently developing different types of imaging hyperspectral instruments for CubeSat and other small satellite applications. All of these instruments utilize Fourier Transform Spectrometer (FTS) interferometer technology, which has been proven on larger space instruments for NASA and NOAA. Most of these instruments are aimed at remote sensing of the earth from low orbit. One example is HyperCube™, which is a hyperspectral mid-wave infrared (MWIR) instrument compatible with 6U CubeSats capable of collecting vertical moisture profiles and three-dimensional winds in the earth’s atmosphere. Another example is Harris’ HyperStare, which is a larger-aperture imaging FTS instrument that provides improved sensitivity and spatial resolution for detection of trace greenhouse gases in the atmosphere. This paper will provide design summaries and performance capabilities of each of these new instrument types. It will also discuss Harris’ newly developed ground station capability for operating small constellations of small satellites. In addition, new FTS technologies that may be suitable for future small satellites will be discussed.

At the Naval Research Laboratory Optical Sciences and Remote Sensing Divisions, a compact hyperspectral imaging sensor has been in development using a method of multi-order spectroscopy using Fabry-Perot etalon arrays. This has allowed for the first broadband, ultra-compact spectrometer. A prototype hyperspectral imaging system is now in development for use with an unmanned aerial vehicle. This system will be a “push-broom system” that scans ground data line by line in a row of pixels forming the hyperspectral datacube and will be georeferenced onto a Digital Surface Model of the ground with location (latitude, longitude, altitude) and attitude (azimuth, pitch, roll) GPS-INS 6-degree of freedom parameters. These parameters will be collected through the use of a high-end modern smartphone with its GPS, accelerometer, gyroscope, barometric pressure, and digital compass sensors. In this paper, we discuss the various sensors and systems being utilized with a smartphone for use with the hyperspectral imaging sensor in development.

Wearable technologies have the ability to change how we perceive, and make decisions about, our health and well-being. In the military, utilizing these emerging technologies in training or operations offers potential life-saving and performance enhancement benefits. Up until now, very limited physiological data collection has been performed due to the overall integration, form-factor, power limitations, and data feedback to the user from wearable monitoring devices. The explosion of the wearables sector in the commercial arena has pushed industry to solve a lot of these issues for the consumer market, allowing for new monitoring opportunities within the military as well. This manuscript discusses a couple of the use cases for wearable technologies within military environments, specifically heat stress injury prevention and performance monitoring during training. Additionally, some preliminary wearable device gold-standard testing is discussed. From the applications described, it can be seen how integration of these technologies has allowed for safer training environments, but also has improved training effectiveness and sustained performance enhancement.

Wearable sensor technologies provide continuous insight into the body’s physiological state and enable real-time feedback for timely intervention. Therefore, they play a critical role in the evaluation and improvement of the health and performance of individuals. Currently, commercialized wearable technologies are only capable of tracking physical activities and vital signs, and fail to unobtrusively access molecular-level information related to the body’s dynamic chemistry. To this end, sweat-based wearable biomonitoring is one of the most promising candidates to merge this gap. Sweat is a rich source of physiological information that can be retrieved non-invasively. It contains many critical analytes, which can be partitioned from blood with some degree of correlation. Therefore, in principle, sweat analysis can be used to provide non-invasive proxy measures of target biomarkers in blood for various clinical and physiological applications. Recent advances in electrochemical sensor development, flexible device fabrication and integration technology, and low power electronics have enabled the development of wearable sweat biosensors. However, despite such progress, the barrier to sweat-based health monitoring continues to be the inability to accurately infer physiologically relevant information from sweat measurements to enable actionable feedback. Here, we briefly review the significance of sweat-based monitoring and recent advances in sweat sensing technologies.

Chronic non-healing wounds, impact over 6.5 million Americans, costs in excess of $25 billion to treat on an annual basis and its incidence is predicted to rise due to the prevalence of obesity and type-2 diabetes. One of the primary complications often associated with chronic wounds is the improper functionality of the peripheral vasculature to deliver O₂-rich blood to the tissue which leads to wound hypoxia. Although hyperbaric oxygen therapy are widely used and accepted as an effective approach to bolster tissue O₂ levels in hypoxic chronic wounds, most of such treatments require bulky equipment and often expose large areas of the body to unnecessarily elevated oxygen concentrations that can damage healthy tissue. In this paper, we present a smart low-cost wound dressing with integrated oxygen sensor and delivery for locally generating and delivering oxygen to selected hypoxic regions on the wound. The dressing is fabricated on a biocompatible water resistant/hydrophobic paper-based substrate with printed optical oxygen sensors and patterned catalytic oxygen generating regions that are connected to a flexible microfluidic systems. Oxygen generation occurs by flowing H²O₂ through the channels and chemical decomposition at the catalyst printed regions on the paper substrate. The hydrophobic paper provides structural stability and flexibility while simultaneously offering printability, selective gaseous filtering, and physical/chemical protection. The fabrication process take advantage of scalable manufacturing technologies including laser processing, inkjet printing, and lamination.

OSHA reports that in 2016 there were 154 fatalities and 1640 non-fatal injuries from electrical exposure.¹ These incidents occurred even at sites with state-of-the art electrical safety programs. Such programs emphasize shutting off sources of electrical energy before exposure, which often occurs during maintenance, installation or other service activities. Nevertheless, exposures still occur, and GE’s research team has been investigating ways of alerting employees to unidentified energized sources. One means of reducing these exposure risks is the use of wearable electronics that would alert the user to energized sources. GE’s Global Research is actively pursuing projects to enhance worker safety with wire-free, lightweight, comfortable devices, and a voltage sensing wristband was developed to provide notification to service and repair workers of the presence of live alternating current circuits. The monitors are not a substitute for personal protective equipment (PPE), but are instead designed to supplement existing training, protocols as a last line and layer of defense. While non-contact voltage sensing devices exist, they do not have the desired sensitivity, comfort, form factor, or "wear and forget" operational mode that is desired for the service workforce. The research team worked closely with the field in specification development and refinement, and in rapidly creating and evaluating prototypes. Flexible circuit, sensor, and band were developed, iterated and field tested in several quick iterative turns. Flexible Hybrid Electronic (FHE) technology elements were used to integrate sensing, communication and computational elements together to create a conformable, bendable wristband. Important lessons were learned about the operating environment, user interface, wearability requirements, sensitivity and repeatability of the devices that drove further design iterations. This band may also serve as a modular platform for further development and enhancement of both the base capabilities and the addition of more diverse sensing capabilities.

Optical neuroimaging technologies aim to observe neural tissue structure and function by detecting changes in optical signals (scatter, absorption, etc…) that accompany a range of anatomical and functional properties of brain tissue. At present, there is a tradeoff between spatial and temporal resolution that is not currently optimized in a single imaging modality. This work focuses on filling the gap between the spatio-temporal resolutions of existing neuroimaging technologies by developing a coherent optics-based imaging system capable of extracting anatomical and functional information across a measurement volume by leveraging a coherent optics-based approach that provides both magnitude and phase information of the sample. We developed a digital holographic imaging (DHI) system capable of detecting these optical signals with a spatial resolution of better than 50 μm over a twenty-five mm² field of view at sampling rates of 300 Hz and higher. The DHI system operates in the near-infrared (NIR) at 1064 nm, facilitating increased light penetration depths while minimizing contributions from overt changes in oxy- and deoxy-hemoglobin concentration present at shorter NIR wavelengths. This label-free imaging method detects intrinsic signals driven by tissue motion, allowing for innately spatio-temporally registered extraction of anatomical and functional signals in vivo. In this work, we present in vivo results from rat whisker barrel cortex demonstrating signals reflecting anatomical structure and tissue dynamics.

We examine the potential for low-intensity focused ultrasound to non-invasively produce small (< 1mm³) focal acoustic fields for precise brain stimulation near the skull. Our goal is to utilize transcranial ultrasonic neuromodulation to transform communications and immersive gaming experiences and to optimize neuromodulation applications in medicine. To begin evaluating possible hardware design strategies for engineering ultrasonic brain interfaces, in the present study we evaluated the skull transmission properties of longitudinal and shear waves as a function of incidence angle for 0–2 MHz. We also employed K-wave and time-reversal numerical simulations to further inspect waveform interactions with modeled layers. Timereversal focusing for single-layer and three-layer skull cases were simulated for three different bandwidth ranges (MHz): Broadband(0–2), 1 MHz(0.4–1.4), and 0.2 MHz(0.4–0.6). Broadband and 1 MHz bandwidths emulate the performance of micromachined or piezo membrane ultrasonic arrays, while 0.2 MHz bandwidth is representative of the performance of conventional piezoelectric ultrasonic transducer. We found the 3dB focal volume was ~0.6 mm for broadband and 1 MHz, with the latter showing a slightly larger sidelobe. In contrast, 0.2 MHz nearly doubled the size of the 3dB focal volume while producing prominent sidelobes. Our results provide initial confirmation that a broadband, ultrasonic, linear array can access the first 15 mm of the human brain, which contains circuitry essential to sensory processing including pre-motor and motor planning, somatosensory feedback, and visual attention. These areas are critical targets for providing haptic feedback via non-invasive neural stimulation.

The Wide-Field Infrared Survey Telescope (WFIRST) is a NASA flagship space observatory expected to launch in the mid-2020s. The mission will probe dark energy as well as carry out broad infrared surveys. WFIRST will also image and spectrally characterize extrasolar planets with a coronagraph at an unprecedented level of sensitivity. The faint planet targets require photon counting detectors to meet the stringent signal-to-noise requirements. The CCD201-20 from Teledyne e2v, an electron multiplying CCD (EMCCD) sensor has been baselined for flight. However, the challenging WFIRST L2 radiation environment must first be considered. Radiation effects from protons and other high energetic particles can hinder the charge transfer efficiency (CTE) of EMCCDs – so-called displacement damage that causes ‘traps’ in the device – as well as affect dark current and other important performance. In order to investigate these effects, we established a photon counting laboratory at JPL which has been used to fully characterize pre- and post-irradiation EMCCD sensors following an extensive radiation campaign. This included studies of read out noise, dark current, clock induced charge and electron multiplication gain. Additionally, we built a scene generator capable of delivering flight-like images on the detector in order to probe degradation of CTE using realistic scenes at the single photon level. Beyond this characterization, we have implemented a technology development program currently underway between JPL and Teledyne e2v to modify the CCD201-20 for radiation hardness in space. These modifications are designed to greatly increase CTE in the presence of traps in addition to reducing the effects of cosmic rays under high EM gain conditions. In parallel to this development, we have also designed techniques that aim to identify damaged regions of the devices and mitigate their effects. I will speak about the challenges of photon counting with EMCCDs in space, with particular focus on WFIRST, in addition to the various technology development and mitigation programs that we have completed.

Currently, there is no SWIR camera that can detect a single photon above cryogenic temperatures. We present the latest results of our Electron Injection (EI) cameras, which show a clear path toward achieving such a formidable goal. We present a fundamental relation between the capacitance of EI injector and its sensitivity to photons, and show experimental results that strongly support it. We also demonstrate the weak temperature dependency of the EI detectors, which allows operation above cryogenic temperature and with compact thermoelectric coolers. Many SWIR applications require stringent timing accuracy. We also present our latest results for ultra-fast SWIR modulators, as fast optical shutter, and their applications in time of flight (ToF) SWIR 3D imaging. Our results show 3D imaging at video rates, with an unprecedented depth resolution due to the low energy consumption in the modulator. Our measurements show our new SWIR modulators consume only ~1 femto-Joule/bit, and with a timing accuracy of ~4 pico-seconds.

Ultraviolet detection is often required to be made in the presence of a strong background of solar radiation which needs to be suppressed, but materials limitations at these wavelengths can impact both filter and sensor performance. In this work, we explore the use of 1D photonic bandgap structures integrated directly onto a Si sensor that can operate with solar blindness. These filters take advantage of the improved admittance with silicon to significantly improve throughput over conventional stand-alone bandpass filter elements. At far ultraviolet wavelengths these filters require the use of non-absorbing dielectrics such as the metal fluoride materials of MgF₂, AlF₃ and LiF. The latest performance of these 1D multilayer filters on Si photodiodes and CCD imaging sensors is demonstrated. We have also extended these 1D structures to more complex multilayers guided by the design concepts of metamaterials and metatronics, and to 2D patterned plasmonic hole array filters fabricated in aluminum. The performance of sensors and test filter structures is presented with an emphasis on UV throughput.

This paper reports on the state of the art of the Quanta Image Sensor (QIS) being developed by Dartmouth. The QIS is a photon-counting image sensor. Experimental 1Mpixel devices have been implemented in a modified backside-illuminated stacked CMOS image sensor process. Without the use of avalanche multiplicative gain, the sensors have achieved room temperature average read noise of 0.22e- rms (analog readout) permitting photon counting, and over 1000fps readout at under 20mW total power dissipation including pads (single-bit digital readout).

The U.S. Army Research Laboratory (ARL) has recently developed an essential research area to research and develop artificially intelligent agents (heterogeneous & distributed) that rapidly learn, adapt, reason & act in contested, austere & congested environments. This talk will focus on the AI&ML research challenges and gaps identified by ARL and highlight some of the recent innovations by ARL researchers.

We discuss our efforts with event-based vision and describe our large-scale, heterogeneous robotic dataset that will add to the growing number of event-based datasets currently publicly available. Our dataset comprises over 10 hours of runtime from a mobile robot equipped with two DAVIS240C cameras and an Astra depth camera randomly wandering in an indoor environment while two other independently moving robots randomly wander in the same scene. Vicon ground truth pose is provided for all three robots. To our knowledge, this is the largest event-based dataset with ground truthed independently moving entities.

This paper introduces an unsupervised compact architecture that can extract features and classify the contents of dynamic scenes from the temporal output of a neuromorphic asynchronous event-based camera. Event-based cameras are clock-less sensors where each pixel asynchronously reports intensity changes encoded in time at the microsecond precision. While this technology is gaining more attention, there is still a lack of methodology and understanding of their temporal properties. This paper introduces an unsupervised time-oriented event-based machine learning algorithm building on the concept of hierarchy of temporal descriptors called time surfaces. In this work we show that the use of sparse coding allows for a very compact yet efficient time-based machine learning that lowers both the computational cost and memory need. We show that we can represent visual scene temporal dynamics with a finite set of elementary time surfaces while providing similar recognition rates as an uncompressed version by storing the most representative time surfaces using clustering techniques. Experiments will illustrate the main optimizations and trade-offs to consider when implementing the method for online continuous vs. offline learning. We report results on the same previously published 36 class character recognition task and a 4 class canonical dynamic card pip task, achieving 100% accuracy on each.

Autonomous quadrotors will soon play a major role in search-and-rescue and remote-inspection missions, where a fast response is crucial. Quadrotors have the potential to navigate quickly through unstructured environments, enter and exit buildings through narrow gaps, and fly through collapsed buildings. However, their speed and maneuverability are still far from those of birds. Indeed, agile navigation through unknown, indoor environments poses a number of challenges for robotics research in terms of perception, state estimation, planning, and control. In this talk, I will show that active vision is crucial to plan trajectories that improve the quality of perception. Also, I will talk about our recent results on event-based vision to enable low latency sensory motor control and navigation in a low light and high dynamic environment, where traditional vision sensors fail.

World View’s Stratollite is a flight system that enables new, edge of space remote sensing and surveillance applications at a fraction of the cost of existing flight platforms. Stratollites offer all the advantages of high-altitude balloons – low-cost, rapid deployment and payload flexibility – with an innovative new development: the ability to fly a variety of trajectories that include navigation to a location and persistent flight over an area. Stratollites can carry a wide variety of commercial payloads (sensors, telescopes, communications arrays, etc.), launch rapidly on demand, and safely return payloads back to earth after mission completion. World View is routinely flying payloads to the edge of space for a variety of government, commercial, and education customers. The applicability of the flight platform is only limited by the imagination of our customers and partners.

Planetary missions are typically confined to navigationally safe environments, leaving areas of interest in rugged and/or hazardous terrain largely unexplored. Identifying and avoiding possible hazards requires dedicated path planning and limits the effectiveness of (semi-)autonomous systems. An adaptable, fully autonomous design is ideal for investigating more dangerous routes, increasing robotic exploratory capabilities, and improving overall mission efficiency from a science return perspective. We introduce hierarchical Lidar-based behavior motifs encompassing actions, such as velocity control, obstacle avoidance, deepest path navigation/exploration, and ratio constraint, etc., which can be combined and prioritized to form more complex behaviors, such as free roaming, object tracking, etc., as a robust framework for designing autonomous exploratory systems. Moreover, we introduce a dynamic Lidar environment visualization tool. Developing foundational behaviors as fundamental motifs (1) clarifies response priority in complex situations, and (2) streamlines the creation of new behavioral models by building a highly generalizable core for basic navigational autonomy. Implementation details for creating new prototypes of complex behavior patterns on top of behavior motifs are shown as a proof of concept for earthly applications. This paper emphasizes the need for autonomous navigation capabilities in the context of space exploration as well as the exploration of other extreme or hazardous environments, and demonstrates the benefits of constructing more complex behaviors from reusable standalone motifs. It also discusses the integration of behavioral motifs into multi-tiered mission architectures, such as Tier-Scalable Reconnaissance

This paper presents a computational architecture to facilitate autonomous decision-making under uncertainty for safe operation of drone-like vehicles. The proposed framework is based on identifying and predicting the occurrence of various risk-factors that affect the safe operation of such vehicles and estimating the likelihood of occurrence of these risk-factors. This analysis is then used to select trajectories for the operation of the vehicle. Feasible trajectories are classified into four different categories: nominal and safe, off-nominal but safe, unsafe and abort the mission, and unsafe and ditch the vehicle. An important challenge in the operation of drones is that there are several sources of uncertainty that affect their operation; these sources of uncertainty arise from wind conditions, imprecise future power-demands, inexact future trajectories, etc. Therefore, it is important to develop a decision-making framework that can incorporate all these sources of uncertainty and make decisions that are robust to the presence of such uncertainty. Potential risk-factors such as dynamic obstacles, battery drain, etc. are identified and the likelihood of occurrence of these risk-factors are predicted preemptively and proactively in order to facilitate risk-informed safety-assured decision-making.

The Automated Global Feature Analyzer^TM (AGFA^TM) is a generically applicable automated sensor-data-fusion, feature extraction, feature vector clustering, anomaly detection, and target prioritization framework. AGFA^TM operates in the respective feature space delivered by the sensor(s). In this paper we provide an overview of the inner workings of AGFA^TM and apply AGFA^TM to planetary imagery, representative of past, current, and future planetary missions, to demonstrate its automated and objective (i.e., unbiased) anomaly detection and target prioritization (i.e., region-of-interest delineation) capabilities. Imaged operational areas are locally processed via a cascade of image segmentation, visual and geometric feature extraction, agglomerative clustering, and principal components analysis. Resulting clusters are labeled based on relative size and location in feature space. Anomalous regions may be considered immediate targets for follow-up in-situ investigation by local robotic agents, which can be directed via autonomous telecommanding, e.g., as part of a Tier-Scalable Reconnaissance mission architecture. These capabilities will be essential for driving fully autonomous C⁴ISR missions of the future, since the speed of light prohibits “real time” Earth-controlled conduct of planetary exploration beyond the Moon.

The invention and development of all-electronically tuned quantum cascade lasers has made it possible to obtain spectral information, covering over 1 μm in the long wave infrared region, regarding absorbers in less than fraction of a millisecond. The electronic tuning is achieved through the use of a acousto-optically generated phase grating in a crystal. As described previously, the acousto-optic modulator (AOM) tuned QCL is capable of switching lasing wavelengths in time of the order of 0.5 μs, regardless of the size of the wavelength step. The wavelength tuning is achieved via change in the acoustic wave RF frequency. Thus, a complete spectrum covering < 1 μm tuning (for example from ~8.5 μm to ~ 9.5 μm) can be obtained in less than 20 μs, when the RF frequency is changes in response to an analog drive. For experimental reproducibility of spectra, we have implemented a digital scanning system that permits selection of step size and step speed.

Using the above system, we have carried out a number of studies to explore the usefulness of rapid scanning QCL systems. One study involves spectroscopy of highly absorbing liquids. Almost all liquids absorb very strongly in the long wave infrared region. We have used attenuated total reflection technique to study liquids such as isopropyl alcohol (IPA), ethanol, water, alcoholic beverage such as vodka, gin and scotch and 2,2,2-trifluroethanol. In each case a complete spectrum from ~8.5 μm to ~ 9.5 μm is recorded in a single shot 500 μs scan.

In another study, we have explored transient mixing of gases (R134A HFC introduced into a fast flowing stream of air) in a flow tube where time dependent spectra of mixing gases are obtained in <600 consecutive shots during a 300 ms time span. I will describe both studies in detail.

The fast spectroscopic study of liquids now opens up the potentially exciting area of real time process monitoring in chemical, biological and food and wine industry. The transient flow spectroscopy study clearly indicates that the AOM tuned QCL system will be of immediate use in supersonic flow studies and in the study of combustion and explosion dynamics.

This presentation introduces the spectroscopic concepts and results enabled by arrays of Distributed Feedback (DFB) QCLs, with each element at a slightly different wavelength than its neighbor. In portable optical systems, such as standoff threat detectors and in situ gas analyzers, this increases analyte sensitivity and selectivity by broadening spectral source coverage while also allowing for extremely fast all-electronic wavelength tuning with no moving parts. This talk will first present the QCL array and its packaging, then move into the description of an integrated prototype standoff detection system, and finally show condensed phase standoff threat detection results from a handheld system from over 1 meter. These data are each compared with legacy contact-based methods to ensure that the technique can be reliably deployed to handheld chemical analysis using suitable chemometric algorithms. The data show how monolithic and all-electronic tuning enables next-generation spectroscopes that are not only more robust and miniature than those that utilize external cavity-tuned lasers, but that are inherently more stable in terms the shot-to-shot amplitude and wavelength parameters. This enhanced stability increases signal to noise for a given configuration (pathlength, averaging time, concentration, etc…). Some discussion of how to maximize the benefits of high speed, highly reproducible tuning is presented, including detector, preamplifier, and digitization considerations.

Significant increase in continuous wave optical power from a single quantum cascade laser (QCL), beyond its current record of 5W, will likely require power scaling with active region lateral dimensions. Active region overheating presents a major technical problem for such broad area devices. Laser thermal resistance can be reduced and laser self-heating can be suppressed by significantly reducing active region thickness, i.e. by reducing number of active region stages and by reducing thickness of each stage in the cascade. The main challenge for quantum cascade lasers with a “thin” active region is to ensure that optical power emitted per active region unit area stays high despite the reduction in active region thickness, a condition critical for the power scaling. Experimental data demonstrating a multi-watt continuous wave operation for broad area QCLs, as well as various aspects of bandgap engineering, waveguide design, and thermal design pertinent to the broad area configuration, are discussed in this manuscript. The critical differences in broad-area laser design between mid-wave and long-wave QCLs is highlighted. Finally, semi-empirical model projections showing that the goal of reaching 20W from a single emitter is realistic is presented.

Advances towards the development of a longwave infrared quantum cascade laser (QCL) based standoff and proximal surface contaminant detection platform are presented with emphasis on developmental test results. The detection platform utilizes reflectance spectroscopy with application to optically thick and thin materials in film and particulate forms including solid and liquid phase chemical warfare agents, toxic industrial chemicals and materials, and explosives. The platform employs an ensemble of broadband Fabry-Perot QCLs with a spectrally selective detector to interrogate target surfaces at 1 to 10s of m standoff. A version of a Subspace Adaptive Cosine Estimator is used for detection and discrimination in high clutter environments. Through speckle reduction, a noise equivalent reflectivity of 0.1% was demonstrated enabling detection limits approaching 0.1 μg/cm² for optically thin films and 2% fill factor for optically thick particulates.

The design, build, and validation of a breadboard version of the QCL-based surface contaminant detector are summarized. Results from developmental testing of contaminated substrates in standoff (5 m range) and proximal (~1 m range) configurations are presented. The test substrates were prepared by the government and Physical Sciences, Inc. and include solid and liquid contaminants at varying surface loadings. Future improvements including an expanded spectral range are discussed.

We are developing a cart-mounted platform for standoff chemical detection technologies based on active broadband infrared imaging spectroscopy. This approach leverages IR quantum cascade lasers, tuned through signature absorption bands (6-11 microns) of the target analytes while illuminating a surface area of interest. An IR focal plane array captures the time-dependent surface response. The image stream forms a hyperspectral image cube comprised of spatial and spectral dimensions as vectors within a detection algorithm. Our current emphasis is on rapid screening. We present the results of recent adaptations of the platform for infrared backscatter imaging spectroscopy (IBIS). Using the mobile platform, we demonstrate standoff detection of trace analytes deposited by sieving onto substrates. We have previously demonstrated standoff trace detection at several meters indoors and in field tests, while operating the lasers below the eye-safe intensity limit (100 mW/cm²). Sensitivity to explosive traces as small as a single grain (~1 ng) has been demonstrated.

Rapidly-swept external-cavity quantum cascade lasers (swept-ECQCLs) provide the broad IR spectral coverage and high spectral brightness required for sensitive multi-chemical standoff detection. The laser source characteristics of swept- ECQCLs can be applied to a variety of standoff applications where gas-phase chemical species concentrations are changing rapidly in time. Some of these applications include standoff measurements in turbulent or chemically reactive plumes, monitoring of industrial emissions from stacks, and real-time monitoring of combustion processes. We have demonstrated and characterized a swept-ECQCL design that is capable of broadband spectral acquisition (~100 cm^-1) at a 5 ms acquisition rate with a high spectral resolution (<0.2 cm^-1). Laser systems based on this swept-ECQCL design have been applied to open-path and standoff measurements in turbulent and reactive chemical plumes of time-varying chemical and isotopic composition. Chemical plume studies have demonstrated the capability of this technology for open-path and standoff chemical sensing applications. In this talk we will present our current progress on the development and application of swept-ECQCL technology for sensitive and rapid multi-chemical open-path measurements in MeOD/MeOH plumes with time-varying isotopic composition at a 40 Hz rate. Preliminary results will also be provided for a 5 m standoff detection of hot CO and CO2 in a turbulent flame using a rapidly-swept mode-hop free (MHF) ECQCL design that is capable of collecting 1-2 cm^-1 MHF spectral windows at an acquisition rate of 1 kHz with a spectral resolution of ~0.001 cm^-1.

Plasma wave electronics approach has a potential for achieving efficient THz emission and sensitive detection using IIIV- based, III-N-based, graphene, Si, SiGe and diamond devices and nanostructure arrays. The physics of these THz plasmonic devices involves collision-dominated, quasi-ballistic, and viscosity dominated regimes of the electron or hole transport. THz plasmonic room temperature detectors have demonstrated excellent performance with potential applications for THz communication and sensing. THz plasmonic emitters based on the Dyakonov-Shur instability and on the “plasmonic boom” concept have promise of achieving high powers at reasonable efficiencies but still should be demonstrated.

THz spectroscopy is one of the key tools for atmospheric science on Earth as well as exploration of the planetary bodies within our solar system. Remote sensing (passive) THz spectroscopy reveals a wealth of information about the nature and composition of atmospheric gasses and is a key sensing method for the detection of water including its isotropic ratios and abundance. This paper discusses key technologies being developed for future THz remote sensing spectrometers at the Jet Propulsion Laboratory, with a focus on low-cost Earth observing missions and deep space planetary missions.

Imaging in the Terahertz (THz) and millimeter-wave (mm-wave) bands offer advantages over doing do in other conventional bands, such as the visible, infrared (IR). The THz band ranges from 300 GHz to 3 THz or in wavelength, 1 mm to 100 μm. These longer wavelengths allows THz radiation to pass unobscured through some materials allowing for imaging hidden threats or defects within such materials. Going further, millimeter-waves cover the spectral band of 30 – 300 GHz, or 10 cm to 1 mm. In addition to passing through denser materials, they also have much less atmospheric absorption, thus are ideal for imaging in adverse weather conditions.

In the THz/mm-wave, the greatest challenge to real-time active imaging was previously the lack of compact sensor arrays. INO has overcome this by optimizing its microbolometer focal plane array (originally developed for the infrared) for the longer wavelengths, covering both the THz and mm-wave bands. The remaining challenge for active imaging is how to obtain useful imagery using coherent sources. INO has been working on improving the quality of the illumination beam over the past few years, as well as designing high quality fast imaging optics. This paper will focus on the different techniques that have been tested across the THz and into the mm-wave bands in both transmission and reflection imaging modes. The impact on image quality will be demonstrated, and their implications to developing useful systems for different applications will be discussed.

We discuss an effective method for the detection and identification of substances irradiated by a broadband THz pulse. The pulse induces high energy level excitation of molecules due to essential non-stationary medium response. This leads to the substance emission at frequencies, which are absent in the incident pulse spectrum. A radiation at these frequencies possesses much penetration force through disordered structures which are usually covered a substance under detection. We propose to use the up-conversion of THz frequencies for the detection and identification of substances. Because of strong dependence of frequency conversion efficiency on its spectral intensity, the frequencies, at which THz pulse energy absorption occurs, are converted with less efficiency in comparison with conversion efficiency of those frequencies.

The broad and slowly varying spectral features of liquids and solids require broadband sources in the mid- to long-wave infrared for their detection and identification. We present here a range of measurements made using uniquely tunable femtosecond optical parametric oscillators, which have enabled stand-off Fourier-transform spectroscopy to be implemented across a large part of the spectral fingerprint region. In this way we have achieved active stand-off detection of liquids on surfaces, of powders and of airborne liquid particles in aerosol form. We discuss the optical parametric oscillator technology, the spectroscopy implementations and the detection capabilities and limitations of the techniques.

Through the European Defence Agency, the Joint Investment Programme on CBRN protection funded the project AMURFOCAL to address detection at stand-off distances with amplified quantum cascade laser technology in the longwave infrared spectral range, where chemical agents have specific absorptions features.

An instrument was developed based on infrared backscattering spectroscopy. We realized a pulsed laser system with a fast tunability from 8 to 10 μm using an external-cavity quantum cascade laser (EC-QCL) and optical parametric amplification (OPA). The EC-QCL is tunable from 8 to 10 μm and delivers output peak powers up to 500 mW. The peak power is amplified with high gain in an orientation-patterned gallium arsenide (OP-GaAs) nonlinear crystal. We developed a pulsed fiber laser acousto-optically tunable from 1880 to 1980 nm with output peak powers up to 7 kW as pump source to realize an efficient quasi-phase matched OPA without any mechanical or thermal action onto the nonlinear crystal. Mixing the EC-QCL and the pump beams within the OP-GaAs crystal and tuning the pump wavelength enables parametric amplification of the EC-QCL from 8 to 10 μm leading to up to 120 W peak power. The output is transmitted to a target at a distance of 10 – 20 m. A receiver based on a broadband infrared detector comprises a few detector elements. A 3D data cube is registered by wavelength tuning the laser emission while recording a synchronized signal received from the target. The presentation will describe the AMURFOCAL instrument, its functional units and its principles of operation.

II-VI binary and ternary chalcogenides (e.g. ZnS, ZnSe; CdZnTe, ) doped with transition metal (TM) ions such as Cr, and Fe are arguably the materials of choice for effective mid-IR lasers potentially covering 1.8-9 µm spectral range. This talk summarizes progress in Cr:ZnS/Se and Fe:ZnSe laser systems, enabling a wide range of tunability (1.8-5.0µm) with output power levels of up to 140 W, as well as Fe doped ternary chalcogenides with tunability potentially extended up to 9 um. TM:II-VI media feature a unique combination of superb ultra-fast laser capabilities with high nonlinearity enabling exceptional output characteristics of polycrystalline Cr:ZnS/Se oscillators in Kerr-Lens-Mode-Locked (KLM) regime over 2-2.6 um and effective up and down conversion of fs pulses via random phase matching (RFM). Extension of mid-IR spectral coverage to 3-8 um is demonstrated by Cr:ZnS KLM laser pumped subharmonic parametric oscillators (OPOs) based on quasi-phase matching in OP-GaAs, and RFM in polycrystalline ZnSe. Fe:II-VI semiconductors are complimentary to Cr doped compounds and 3-8 um KLM ultrafast oscillators based on Fe doped chalcogenides are feasible. Another important feature of Fe:II-VI media is excellent energy storage capability at 77-200K (~60 µs luminescence life time) enabling efficient Q-switched regime and high energy amplification of ns and ultrafast pulses. One of the major problems in the development of CW, gain switched, Q-switched and KLM ultrafast Fe:II-VI lasers was the absence of convenient pump sources overlapping with absorption band (2.7-4.5 um) of Fe: gain media. Potential utilization of Quantum Cascade Lasers (QCL) as pump sources of Fe:II-VI lasers will be discussed in the form QCL-solid state laser hybrid platforms as well as Fe doped active layers integrated in QCL structures.

We present a new platform for mid-infrared (MIR) dual-comb spectroscopy, based on a pair of ultra-broadband subharmonic optical parametric oscillators (OPOs) pumped by two phase-locked thulium-fiber combs. Our system provides fast (7 ms for a single interferogram), moving-parts-free, simultaneous acquisition of 350,000 spectral data points, spaced by 115-MHz intermodal interval over 3.1–5.5 μm spectral range. Parallel detection of 22 trace molecular species in a gas mixture, including isotopologues containing such isotopes as ¹³C, ¹⁸O, ¹⁷O, ¹⁵N, ³⁴S, ³³S and ²H (deuterium), with part-per-billion sensitivity and sub-Doppler resolution has been demonstrated. We also show that by utilizing Kerr-lens mode-locked Cr:ZnS lasers operating at λ≈2.35 μm one can create MIR frequency combs spanning almost two octaves in wavelength.

Solder bump array formation is a key step in micro-array flip-chip fabrication process. Fabrication of solder bumps with small diameter and high aspect ratio geometries is necessary for high pixel density and low noise detectors. Indium is an attractive material for low temperature sensing application due to its cryogenic stability, good thermal and electrical conductivity, and ductile nature. In this paper, fill quality of micro-patterned arrays with thermally evaporated indium thin film is studied. Impact of indium evaporation rate, substrate temperature, bump aspect ratio and bump array pitch on bump formation in the via trenches is investigated. The indium bump formation dynamics are discussed in detail. State-of-art indium bump size with high aspect ratio and small array pitch is achieved, along with high uniformity and low defect density.

This paper addresses the problem of motion analysis performed from digital data captured by a network of motion sensors scattered over a field of interest where 3D+T motion analysis is per- formed. Motion analysis, as referred here for digital signals, proceeds through consecutive steps of detection, motion-oriented classification, parameter estimation and tracking. The scheme proposed in this paper is relevant to applications that can be found in medicine, earth science, surveillance and defense. The major challenges involved in the feasibility of this network are as follows: signal sampling from a sensor network, photodetection and optimal strategy for cope with energy harvesting and wireless communication capabilities. The motion sensors implement wireless communications to some gateway or data sink that relays the collected information to a remote central station. Motion sensors are assigned to catch motion with high sensitive sparsely distributed sensors and to build the trajectories. Other sensors can be added to the system for specific purpose like video camera. Video cameras are assigned to catch high resolution images or videos with densely and regularly distributed sensors to perform pattern classification and recognition. The central station implements the motion analysis algorithm. Motion analysis is performed as a dual control referring to both an accurate model based on theoretical mechanics and an adaptive learning system based on a supervised neural network. This paper describes the effective components of the system which are namely the sensor layer, the telecommunication layer, and the application layer.

Recent improvements in microparticle synthesis and handling have prompted new research into the engineering and fabrication of single and multilayered microspheres through traditional physical and chemical vapor depositions. At the University of Delaware, we have developed a custom batch coating process utilizing a vibro-fluidized mixing vessel to deposit thin-films onto the surface of microparticle substrates through R.F. magnetron sputtering. This process opens up a number of design possibilities for single and multilayered microsphere technologies that can be used to improve the optical performance of several optical filtering applications. Through the use of custom design and simulation software, we have optimized a number of filter designs and validated these findings through commercial software. Specifically, we have aimed to improve upon the mass extinction performance seen by traditional materials in the long wave infrared spectrum (LWIR, λ=8-12μm). In order to do this, we have run a series of experiments aimed at creating ultra-lightweight metallic hollow-spheres. Aluminum thin-films have been successfully deposited onto a number of substrates including hollow glass microspheres, high density polyethylene microspheres, and polystyrene foam spheres. By depositing the thin-films onto polymer substrates we have been able to remove the solid core after deposition through a thermal decomposition or chemical dissolution process, in an effort to reduce particle mass and improve mass extinction performance of the filter. A quantum cascade laser measurement system has been used to characterize the optical response of these fabricated aluminum hollow-spheres and have largely agreed with the expected simulated results.

We report the experimental results of a 40-stage InP-based quantum cascade laser (QCL) structure grown on a 6-inch GaAs substrate with metamorphic buffer (M-buffer). The laser structure’s strain-balanced active region was composed of Al_0.78In_0.22As/In_0.73Ga_0.27As and an all-InP, 8 μm-thick waveguide. The wafer was processed into ridge-waveguide chips (3mm x 30 μm devices) with lateral current injection scheme. Devices with high reflection coating delivered power in excess of 200 mW of total peak power at 78K, with lasing observed up to 230K. Preliminary reliability testing at maximum power showed no sign of performance degradation after 200 minutes of runtime. Measured characteristic temperatures of T0 ≈ 460 K and T1 ≈ 210 K describes the temperature dependence for threshold current and slope efficiency, respectively, in the range from 78K to 230K. Partial high reflection coating was used on the front facet to extend the lasing range up to 303K.

We report on highly sensitive and flexible biosensors for noninvasive lactate and alcohol monitoring in human perspiration based on zinc oxide (ZnO) nanostructures that does not require linker layer for surface functionalization due to the high isoelectric point of ZnO. Towards fabrication of the biosensors, two-dimensional (2D) ZnO nanoflakes (NFs) were synthesized on flexible polyethylene terephthalate (PET) substrates employing single step sonochemical method after which lactate oxidase (LOx) and anti-body for ethyl glucuronide (EtG)-a metabolite of ethanol were immobilized atop without a linker layer. The cyclic voltammetry (CV) measurements in the concentration range of 10pM-10μM for lactate and 4.5 μM-0.45 M for EtG yielded minimum limit of detection of 10 pM and 4.5 μM, respectively for the electrode area of 0.5 × 0.5 cm². Moreover, lactate sensor with ZnO NF electrodes demonstrated four times higher sensitivity compared to the ones with gold electrode that required DTSP linker layer for surface functionalization. High isoelectric point allows a direct, stable pathway for rapid electron transport without any mediator when an analyte is immobilized on NFs and improves electron transfer rate.

In this work, we have demonstrated an optical surface Plasmon resonance (SPR) sensor head that is based on an inverted rib dielectric waveguide, in which the resonance wavelength of the surface plasmon excited at the gold metal-dielectric interface changes in relation to changes of the environment at the top metal surface. The inverted-rib waveguide of the SPR sensor head is made of a layer of SU-8 polymer with a refractive index of 1.5 while the lower cladding layer consists of silicon oxynitride (SiO_xN_y) with a refractive index of 1.526. The top surface is coated with a 50 nm thick layer of gold. The SPR sensor head was designed to allow monitoring of analyte media with a refractive index ranging from 1.44 to the 1.502. Using a set of reference liquids representing the analyte medium, the sensitivity of the SPR sensor was measured using a broadband light source and a optical spectrum analyzer. It was found that with a liquid of 1.442 refractive index in contact with the gold metal, a sharp resonance dip in the transmission spectrum occurred at 1525 nm and its position shifted to 1537 nm when a liquid of 1.502 was used. From these measurements, the sensitivity of the sensor devices wasdetermined to be S = 232 nm.RIU^-1. We demonstrate that this device can potentially be totally integrated with a wavelength tunable light source, a photodetection unit as well as a liquid delivery system via microfluidic channels making it an extremely compact unit.

Surface polaritons have been shown to provide subwavelength confinement. Surface phonon polaritons (SPhPs), electromagnetic waves coupled to lattice vibrations in a polar dielectric, allow for highly confined propagating modes beyond the limit of diffraction within the mid to long infrared (IR). In recent years, it has been shown that hybrid plasmonic and phononic waveguides can support long-range hybrid modes that result from the coupling between SPhPs and a high index dielectric tracer. This work investigates the use of a hybrid phononic waveguide as a building block of a ring resonator that operates in the long wave infrared (LWIR) spectrum. Critical coupling condition and trade-off between ring diameter and output power are characterized. LWIR ring resonators hold promise for numerous applications including modulation, biosensing, photodetectors, and chemical sensing.

Advances in medical device engineering, as well as our continuously increasing understanding of brain function, has increased the safety, reliability, and efficacy of neuromodulation methods for regulating human behavior over the past couple decades. Clinical neuromodulation devices are becoming frequently used for treating neurological and psychiatric disorders. Most clinical methods however rely on surgically implanted electrodes, such as those incorporated by deep-brain stimulation systems to treat Parkinson’s disease. Several different methods of noninvasive neuromodulation also exist and have been used to alter brain activity for research applications or to treat some nervous systems disorders. Some noninvasive methods involve delivering electrical currents or electromagnetic pulses to specific peripheral nerves or brain targets in order to modulate nervous system activity. Other more recently developed methods use focused ultrasound to noninvasively modulate human brain circuits or nerves at high spatiotemporal resolutions. Beyond the utility of restoring loss of function in therapeutic embodiments, these safety benchmarks have encouraged the widespread investigation of several different types of neuromodulation methods for their potential to increase gains in the performance and function of healthy individuals. Noninvasive neuromodulation has been shown to enhance brain plasticity and physical performance, accelerate learning, increase attention, and improve sleep. Additive gains have been shown when combining neuromodulation devices with biosensors and virtual immersion gaming systems as human computer interfaces. An overview of how electrical and ultrasonic neuromodulation methods embodied as human computer interfaces are being developed for enhancing the performance of military operators and defense personnel is provided in the present paper.