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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 145 records · Page 8
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Extreme ultraviolet quantum efficiency of opaque alkali halide photocathodes on microchannel plates

Comprehensive measurements are presented for the quantum detection efficiency (QDE) of the microchannel plate materials CsI, KBr, KCl, and MgF2, over the 44-1800 A wavelength range. QDEs in excess of 40 percent are achieved by several materials in specific wavelength regions of the EUV. Structure is noted in the wavelength dependence of the QDE that is directly related to the valence-band/conduction-band gap energy and the onset of atomic-like resonant transitions. A simple photocathode model allows interpretation of these features, together with the QDE efficiency variation, as a function of illumination angle.

Siegmund, O. H. W.↗
NASA NTRS1969

The Quantasyn, an improved quantum detector

Quantasyn provides absolute measurement of radiation flux in the range 1000 A to 4500 A and into the vacuum ultraviolet. This radiation detector cimbines the high quantum efficiency and inherent linearity of the silicon solar cell with the constant quantum response of the fluorescent organic compound liumogen.

Gorstein, M.↗
NASA NTRS1994

High Performance InGaAs/GaAs Quantum Well Infrared Photodetectors

We have measured the optical and transport properties of In(0.2)Ga(0.8)As/GaAs quantum well infrared photodetectors based on bound-to-bound, bound-to-quasibound, and bound-to-continuum intersubband transitions. Excellent hot electron transport and high detectivity D*=1.8 x 1O(exp 10) cm square root of Hz/W (at lambda(sub p)=16.7 microns) were achieved at temperature T=40 K.

Gunapala, S. D.↗
NASA NTRS1991

Lateral modes of broad area semiconductor lasers - Theory and experiment

Calculations of the lateral modes of an ideal broad area laser, including the nonlinear interaction between the carriers and the optical field, are made. The results include periodically modulated near fields and single- and double-lobed far fields similar to those previously measured. The unsaturable losses are higher and quantum efficiencies are lower than those determined from plane-wave approximations. Broad area InGaAs-GaAlAs-GaAs quantum-well lasers were fabricated and measured and found to closely agree with the theory in near, far, and spectrally resolved near fields. An occultation experiment on the far field confirms previously predicted unstable resonatorlike modes with V-shaped fronts.

Lang, Robert J.↗
NASA NTRS1990

A 128 x 128 InGaAs detector array for 1.0 - 1.7 microns

A two-dimensional 128 x 128 detector array for the 1.0 - 1.7 micron spectral region has been demonstrated with indium gallium arsenide. The 30 micron square pixels had 60 micron spacing in both directions and were designed to be compatible with a 2D Reticon multiplexer. Dark currents below 100 pA, capacitance near 0.1 pF, and quantum efficiencies above 80 percent were measured. Probe maps of dark current and quantum efficiency are presented along with pixel dropout data and wafer yield which was as high as 99.89 percent (7 dropouts) in an area of 6528 pixels and 99.37 percent (103 dropouts) over an entire 128 x 128 pixel region.

Olsen, G.↗
NASA NTRS1993

Disturbance, the uncertainty principle and quantum optics

It is shown how a disturbance-type uncertainty principle can be derived from an uncertainty principle for joint measurements. To achieve this, we first clarify the meaning of 'inaccuracy' and 'disturbance' in quantum mechanical measurements. The case of photon number and phase is treated as an example, and it is applied to a quantum non-demolition measurement using the optical Kerr effect.

Martens, Hans↗
NASA NTRS2014

New and Better Near-Infrared Detectors for JWST Near Infrared Spectrograph

ESA and NASA recently selected two 5 m cutoff Teledyne H2RG sensor chip assemblies (SCA) for flight on the James Webb Space Telescope (JWST) Near Infrared Spectrograph (NIRSpec). These HgCdTe SCAs incorporate Teledynes improved barrier layer design that eliminates the degradation that affected earlier JWST H2RGs(Rauscher et al. 2012a). The better indium barrier, together with other design changes, has improved the performance and reliability of JWSTs SCAs. In this article, we describe the measured performance characteristics that most directly affect scientific observations including read noise, total noise, dark current, quantum efficiency (QE), and image persistence. As part of measuring QE, we measured the quantum yield as a function of photon energy,, and found that it exceeds unity for photon energies E (2.65.2) Eg, where Eg is the HgCdTe bandgap energy. This corresponds to. 2 m for NIRSpecs 5 m cutoff HgCdTe. Our measurements agree well with a previous measurement by McCullough et al. (2008) for. 1.3. For 1.3, we find a slower increase in with photon energy than McCullough et al. did. However, and as McCullough et al. note, their two state model of the yield process is not valid for large 1.

New and Better↗
NASA NTRS1974

CO2 photodissociation and vibrational excitation in the planetary atmospheres

The principal subjects of investigation were the determination of the CO2 photodissociation quantum yields at the wavelengths from 1200 A to 1500 A, and the efficiency of electronic-to-vibrational energy transfer in the systems 0(1D) + CO, N2, CO2 yields 0(3P) + CO N2, CO2 vibrational energies. Measurements on the photodissociation quantum yield of CO2 in the 1200-1500 A region show that it is wavelength dependent, and for the six atomic line sources used, the quantum yield varied from 0.2 to 0.8. The data appear to fit the interpretation of stable CO2 bound states mixed with repulsive or predissociating states, since the low quantum yields coincide with the maximum structure in the CO2 absorption spectrum. The first reliable measurements were made on the efficiency of electronic-to-vibrational energy transfer in the systems 0(1D)-CO and 0(1D)-N2, using a uv resonance fluorescence technique. The 0(1D)-CO2 interaction was investigated by infrared techniques.

Slanger, T. G.↗
NASA NTRS1993

Experimental verification of the photodiode theory of SIS mixers

The authors describe the characterization and interpretation of the performance of SIS receivers within the framework of the photodiode theory of mixing. The quantum efficiency plays a dominant role in the theory, and a simple method of accurately measuring this parameter is presented. It is demonstrated that the quantum efficiency measurements can be conveniently made on a standard radio astronomy receiver and combined with the usual hot and cold load characterization to improve the understanding of the receiver's performance. The measurements verify that the photodiode theory of mixing accurately describes the receiver noise even at local-oscillator power levels well above the linear response range. The results for receivers operating at 100 and 240 GHz verify the utility of this approach. These methods should also prove useful in evaluating submillimeter receivers.

Woody, David P.↗
NASA NTRS2012

320 x 256 Complementary Barrier Infrared Detector Focal Plane Array for Long-Wave Infrared Imaging

A 320 x 256 Complementary Barrier Infrared (CBIRD) focal plane array for long-wavelength infrared (LWIR) imaging is reported. The arrays were grown by molecular beam expitaxy (MBE) with a 300 period 1.9 um thick absorber. The mean dark current density of 2.2 x 10-4 A/cm2 was measured at an operating bias of 128 mV with a long wavelength cutoff of 8.8 ?m observed at 50% of the peak. The maximum quantum efficiency was 54% measured at 5.6 ?m. Operating at T = 80K, the array yielded an 81% fill factor with 97% operability. Good imagery with a mean noise equivalent different temperature (NE?T) of 18.6 mK and a mean detectivity of D* = 1.3 x 1011 cm-Hz1/2/W was achieved. The substrate was thinned using mechanical lapping and neither an AR coating nor a passivation layer was applied. This article provides the details of the fabrication process for achieving low-dark current LWIR CBIRD arrays. Discussion for an effective hard mask for excellent pattern transfer is given and appropriate mounting techniques for good thermal contact during the dry etching process is described. The challenges and differences between etching large 200 ?m test diodes and small 28 ?m FPA pixels are given.

Focal Plane Arrays (FPA)↗
NASA NTRS1981

OCS photolysis and absorption in the 200- to 300-nm region

A continuum source with three different interference filters and two different monochromatic sources were used to photolyze OCS in the region from 200 nm to 300 nm. The total quantum yield for the production of CO was measured, and the results indicate a primary quantum yield of 0.72 + or - 0.08. Absorption cross sections for OCS measured at 0.5-nm intervals are reported as well as the percent change in absorption upon cooling to 195 K. The structured features in the absorption are reinvestigated and discussed.

Rudolph, R. N.↗
NASA NTRSDate not supplied

Logical Shadow Tomography: Efficient Estimation of Error-mitigated Observables

In near-term quantum applications, reducing errors and improving device reliability is an essential task. Towards these ends, various techniques have been introduced in recent literature, collectively referred to as quantum error mitigation techniques, for reducing errors in pre-fault-tolerant devices. Here, we introduce logical shadow tomography as a versatile error mitigation method. Our technique uses a stabilizer code to encode information in a logical state. Instead of doing active error correction, quantum states will be measured at the end of computation via shadow tomography and non-logical errors are projected out in the classical post-processing. Relative to quantum subspace expansion which requires O(2(M-1)L) experiments to estimate an logical Pauli observable encoded by an [[M, L, d]] code, our technique only requires 2L experiments, an important practical reduction in resources.

Hong-Ye Hu↗
NASA NTRS1987

Absolute I(asterisk) quantum yields for the ICN A state by diode laser gain-vs-absorption spectroscopy

Absolute I(asterisk) quantum yields have been measured as a function of wavelength for room temperature photodissociation of the ICN A state continuum. The yields are obtained by the technique of time-resolved diode laser gain-vs-absorption spectroscopy. Quantum yields are evaluated at seven wavelengths from 248 to 284 nm. The yield at 266 nm is 66.0 + or - 2 percent and it falls off to 53.4 + or - 2 percent and 44.0 + or - 4 percent at 284 and 248 nm, respectively. The latter values are significantly higher than those obtained by previous workers using infrared fluorescence. Estimates of I(asterisk) quantum yields obtained from analysis of CN photofragment rotational distributions, as discussed by other workers, are in good agreement with the I(asterisk) yields reported here. The results are considered in conjunction with recent theoretical and experimental work on the CN rotational distributions and with previous I(asterisk) quantum yield results.

Hess, Wayne P.↗
NASA NTRS1994

Bloch vector projection noise

In the optical measurement of the Bloch vector components describing a system of N two-level atoms, the quantum fluctuations in these components are coupled into the measuring optical field. This paper develops the quantum theory of optical measurement of Bloch vector projection noise. The preparation and probing of coherence in an effective two-level system consisting of the two ground states in an atomic three-level lambda-scheme are analyzed.

Wang, Li-Jun↗
NASA NTRS1989

Measurements of argon broadened Lorentz width and pressure-induced line shift coefficients in the nu4 band of (C-12)H4

Room temperature argon broadened halfwidth and pressure-induced line shift coefficients have been determined for 118 transitions in the nu4 band of (C-12)H4 from analysis of high resolution laboratory absorption spectra recorded with the McMath Fourier transform spectrometer operated on Kitt Peak by the National Solar Observatory. Transitions up to J-double-prime = 12 have been measured using a nonlinear least-squares spectral fitting procedure. The variation of the measured halfwidth coefficients with symmetry type and rotational quantum number is very similar to that measured previously for N2 and air broadening, but the absolute values of the argon broadening coefficients are all smaller. On average, the ratio of the argon broadened halfwidth coefficient to the corresponding N2 broadened halfwidth coefficient is 0.877 + or - 0.017 (2 Sigma). More than 95 percent of the pressure-induced shifts are negative with values ranging from -0.0081 to +0.0055/cm atm. The pressure shifts in argon are nearly equal to corresponding values measured previously in N2 and air.

Rinsland, Curtis P.↗
NASA NTRS1992

Anomalous capacitance of quantum well double-barrier diodes

The S-parameters of several different quantum well double barrier diodes have been measured. A technique has been developed for measuring whisker contacted diodes with an HP 8510B automatic network analyzer. Special coaxial mounts using K-connectors were designed to enable measurements up to 20 GHz. The voltage-dependent conductance and capacitance were derived from the measured reflection coefficient of each device. The C/V characteristics were observed to exhibit an anomalous increase at voltages corresponding to the negative differential resistance region (NDR). These are the first reported S-parameter measurements in the negative differential resistance region of quantum well double barrier diodes. A theory is presented that explains, in part, the observed results.

Boric, Olga↗
NASA NTRSDate not supplied

Quantum Information Systems at NASA Glenn Research Center

NASA Glenn Research Center is focused on supporting NASA goals in several mission areas from Space Exploration and Aeronautics to Science. NASA GRC is exploring how quantum metrology, models, and free-space testbeds can be integrated with NASA’s aerospace competency needs to provide an understanding of how spaceflight components work together in Quantum Information Systems. In this presentation an overview of potential focus areas for quantum systems along with current efforts to enable research and analysis of quantum systems for NASA applications will be discussed. As such, we provide an overview of device measurement capability within NASA’s Quantum Metrology Laboratory (NQML), dynamic quantum network modeling via the NASA Quantum Communications Analysis Suite (NQCAS) simulation tool, and plans for instituting an aero quantum testbed platform.

quantum↗