Test Pixels For High-Temperature Infrared Scene Projection

High pixel temperatures for IR scene projector arrays face materials challenges of oxidation, diffusion, and recrystallization. For cost effective development of new high-temperature materials, we have designed and fabricated simplified pixels for testing. These consist of resistive elements, traces, and bond pads sandwiched between dielectric layers on Si wafers. Processing involves a pad exposure etch, a pixel outline etch, and an undercut etch to thermally isolate the resistive element from the substrate. Test pixels were successfully fabricated by electron-beam lithography using a combination of wet and dry etching

Planetary Atmospheres Minor Species Sensor (Pamss)

The Planetary Atmospheres Minor Species Sensor (PAMSS) is an ultra-trace gas sensor. This paper reports its transition from a Technical Readiness Level of 4 (TRL4) to TRL 5 and an established path forward to TRL6. This report describes tests of PAMSS in chambers that simulate a balloon flight to 30 km. Lessons learned inform a number of improvements, which are being implemented for a balloon flight planned for June 2014. © 2014 SPIE

Junctionless thin-film ferroelectric oxides for photovoltaic energy production

Streaming Process for Electrode-less Electrochemical Deposition (SPEED) method is used to create complex thin-film structures, such as KBNNO, in a single step, in contrast to hydrothermal approaches with separate nanoparticle growth and deposition processes. This new ferroelectric oxide [KNbO 3]1-x[BaNi1/2Nb1/2O 3-δ]x or KBNNO has an alloy-tunable band gap as low as 1.1 eV, so that its absorption can be tailored to match the solar spectrum. At the same time, it has a reasonably large polarization allowing for charge separation across the bulk, sizeable photocurrents, and open-circuit voltages Voc that exceed the band gap, potentially leading to efficiencies that exceed those possible for standard pnjunction cells. Physical characterization of KBNNO films demonstrate the microstructure and stoichiometry of SPEEDproduced thin-films, ratio of elements needed to achieve an ideal band gap of ~1.39 eV, the effect on film chemistry, microstructure, and band gap of annealing, the practical separation of excited carriers at room temperature, the maximum achievable polarization and its temperature dependence, and the conditions for ideal poling. Photovoltaic characterization of KBNNO cells will determine the efficiency, the relative strengths of dark and photo currents, the open circuit voltage, the short circuit current, and cell fill factor (FF). © 2014 SPIE

Plasmon Resonance Response To Millimeter-Waves Of Grating-Gated Ingaas/Inp Hemt

Tunable resonant absorption by plasmons in the two-dimensional electron gas (2DEG) of grating-gated HEMTs is known for a variety of semiconductor systems, giving promise of chip-scale frequency- agile THz imaging spectrometers. In this work, we present our approach to measurement of electrical response to millimeter waves from backward-wave oscillators (BWO) in the range 40-110 GHz for InP-based HEMTs. Frequency-modulation of the BWO with lock-in amplification of the source-drain current gives an output proportional to the change in absorption with frequency without contribution from non-resonant response. This is a first step in optimizing such devices for manportable or space-based spectral-sensing applications. © 2010 SPIE

Junctionless Thin-Film Ferroelectric Oxides For Photovoltaic Energy Production

Streaming Process for Electrode-less Electrochemical Deposition (SPEED) method is used to create complex thin-film structures, such as KBNNO, in a single step, in contrast to hydrothermal approaches with separate nanoparticle growth and deposition processes. This new ferroelectric oxide [KNbO 3]1-x[BaNi1/2Nb1/2O 3-δ]x or KBNNO has an alloy-tunable band gap as low as 1.1 eV, so that its absorption can be tailored to match the solar spectrum. At the same time, it has a reasonably large polarization allowing for charge separation across the bulk, sizeable photocurrents, and open-circuit voltages Voc that exceed the band gap, potentially leading to efficiencies that exceed those possible for standard pnjunction cells. Physical characterization of KBNNO films demonstrate the microstructure and stoichiometry of SPEEDproduced thin-films, ratio of elements needed to achieve an ideal band gap of ~1.39 eV, the effect on film chemistry, microstructure, and band gap of annealing, the practical separation of excited carriers at room temperature, the maximum achievable polarization and its temperature dependence, and the conditions for ideal poling. Photovoltaic characterization of KBNNO cells will determine the efficiency, the relative strengths of dark and photo currents, the open circuit voltage, the short circuit current, and cell fill factor (FF). © 2014 SPIE

Plasmon Absorption In Grating-Coupled Inp Hemt And Graphene Sheet For Tunable Thz Detection

The two-photon absorption (2PA) spectrum of an organic single crystal is reported. The crystal is grown by self-nucleation of a subsaturated hot solution of acetonitrile, and is composed of an asymmetrical donor-π-acceptor cyanine-like dye molecule. To our knowledge, this is the first report of the 2PA spectrum of single crystals made from a cyanine-like dye. The linear and nonlinear properties of the single crystalline material are investigated and compared with the molecular properties of a toluene solution of its monomeric form. The maximum polarization-dependent 2PA coefficient of the single crystal is 52 ± 9 cm/GW, which is more than twice as large as that for the inorganic semiconductor CdTe with a similar absorption edge. The optical properties, linear and nonlinear, are strongly dependent upon incident polarization due to anisotropic molecular packing. X-ray diffraction analysis shows π-stacking dimers formation in the crystal, similar to H-aggregates. Quantum chemical calculations demonstrate that this dimerization leads to the splitting of the energy bands and the appearance of new red-shifted 2PA bands when compared to the solution of monomers. This trend is opposite to the blue shift in the linear absorption spectra upon H-aggregation. © 2012 American Chemical Society

Inp- And Graphene-Based Grating-Gated Transistors For Tunable Thz And Mm-Wave Detection

Tunable resonant absorption by plasmons in the two-dimensional electron gas (2DEG) of grating-gated HEMTs is known for a variety of semiconductor systems, giving promise of chip-scale frequency-agile THz imaging spectrometers. We present our calculations of transmission spectra and resonant photoresponse due to plasmons in InPand graphene-based HEMTs at millimeter and THz wavelengths. Our experimental approach to measurement of electrical response is also described. Potential applications include man-portable or space-based spectral-sensing. © 2011 Copyright Society of Photo-Optical Instrumentation Engineers (SPIE)

Planar Integrated Plasmonic Mid-Ir Spectrometer

The convergence of silicon photonics and infrared plasmonics allows compact, chip-scale spectral sensors. We report on the development of a compact mid-IR spectrometer based on a broad-band IR source, dielectric waveguides, a transformer to convert between waveguide modes and surface plasmon polaritons (SPP), an interaction region where analyte molecules are interrogated by SPPs, an array of ring resonators to disperse the light into spectral components, and photodetectors. The mid-IR light source emits into a dielectric waveguide, leading to a region that allows coupling of the incident photons into SPPs. The SPPs propagate along a functionalized metal surface within an interaction region. Interactions between the propagating SPP and any analytes bound to the surface increase loss at those wavelengths that correspond to the analyte vibrational modes. After a suitable propagation length the SPP will be coupled back into a dielectric waveguide, where specific wavelength components will be out-coupled to detectors by an array of ring resonators. We have selected a 3.4 micron LED as the IR source, based on both cost and performance. Initial experiments with circular waveguides formed from GLSO glass include measurement of the loss per mm. Electrodynamic simulations have been performed to inform the eventual Si taper design of the proposed photonic/plasmonic transformer. The SPP propagation length necessary for a discernible change in the signal due to absorption in the interaction region has been estimated to be on the order of 1 mm, well within the bounds of calculated propagation lengths for SPPs on Au. © 2012 SPIE

Planetary Atmospheres Minor Species Sensor Balloon Flight Test To Near Space

The Planetary Atmospheres Minor Species Sensor (PAMSS) is an intracavity laser absorption spectrometer that uses a mid-infrared quantum cascade laser in an open external cavity for sensing ultra-trace gases with parts-per-billion sensitivity. PAMSS was flown on a balloon by Near Space Corporation from Madras OR to 30 km on 17 July 2014. Based on lessons learned, it was modified and was flown a second time to 32 km by World View Enterprises from Pinal AirPark AZ on 8 March 2015. Successes included continuous operation and survival of software, electronics, optics, and optical alignment during extreme conditions and a rough landing. Operation of PAMSS in the relevant environment of near space has significantly elevated its Technical Readiness Level for trace-gas sensing with potential for planetary and atmospheric science in harsh environments

Inp- And Graphene-Based Grating-Gated Transistors For Tunable Thz And Mm-Wave Detection

Plasmon excitation in the two dimensional electron gas (2DEG) of grating-gated high electron mobility transistors (HEMTs) gives rise to terahertz absorption lines, which may be observed via transmission spectroscopy. Such absorption resonances may alter the channel conductance, giving a means for tunable terahertz detection. The transmission spectrum may be calculated analytically by making simplifying assumptions regarding the electron distribution. Such assumptions can limit the usefulness of such analytical theories for device optimization. Indeed, significant differences between experimentally observed resonances and theory have been noted and explained qualitatively as due to additional, unanticipated, sheets of charge in the device. Here, we explore finite element method (FEM) simulations, used to obtain realistic carrier profiles. Simulated plasmon spectra do not support previous explanations of red-shifting due to interactions with additional neighboring charge distributions. Simulations do show unexpected plasmon resonances associated with the unanticipated sheet charge, named virtual-gate, as well as the expected resonances associated with the 2DEG. Plasmonic modes determined from these investigations are able to account for the measured absorption lines which were previously thought to be red-shifted 2DEG plasmons. Additionally, the same simulation approach was applied to proposed graphene-based devices to investigate their plasmon resonance spectra. © 2012 SPIE