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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 379 records · Page 21
All sourcesNASA NTRSDOE OSTI
NASA NTRS1990

Linear laser diode arrays for improvement in optical disk recording for space stations

The design and fabrication of individually addressable laser diode arrays for high performance magneto-optic recording systems are presented. Ten diode arrays with 30 mW cW light output, linear light vs. current characteristics and single longitudinal mode spectrum were fabricated using channel substrate planar (CSP) structures. Preliminary results on the inverse CSP structure, whose fabrication is less critically dependent on device parameters than the CSP, are also presented. The impact of systems parameters and requirements, in particular, the effect of feedback on laser design is assessed, and techniques to reduce feedback or minimize its effect on systems performance, including mode-stabilized structures, are evaluated.

Alphonse, G. A.↗
NASA NTRS1990

Tunable diode laser IR spectrometer for in situ measurements of the gas phase composition and particle size distribution of Titan's atmosphere

A new instrument, the Probe Infrared Laser Spectrometer (PIRLS), is described for in situ sensing of the gas composition and particle size distribution of Titan's atmosphere on the NASA/ESA Cassini mission. For gas composition measurements, several narrow-band (0.0001/cm) tunable lead-salt diode lasers operating near 80 K at selected mid-IR wavelengths are directed over a path length defined by a small reflector extending over the edge of the probe spacecraft platform; volume mixing ratios of 10 to the -9th should be measurable for several species of interest. A cloud-particle-size spectrometer using a diode laser source at 780 nm shares the optical path and deployed reflector; a combination of imaging and light scattering techniques is used to determine sizes of haze and cloud particles and their number density as a function of altitude.

Webster, Christopher R.↗
NASA NTRS1989

Computer processing of tunable diode laser spectra

A computer-controlled tunable diode laser spectrometer and spectral analysis software are described. The three-channel system records simultaneously the transmission of a subject gas, a temperature-stabilized etalon, and a calibration gas. The software routines are applied to diode laser spectra of HNO3 and NO2 to illustrate the procedures adopted for conversion of raw spectral data to useful transmission and harmonic spectra. Extraction of line positions, absorption intensities, collisional broadening coefficients, and gas concentrations from recorded spectra is also described.

May, Randy D.↗
NASA NTRS1989

Space-qualified laser diode assembly for the NASA/DDLT program

A space-qualified module incorporating a high power semiconductor diode laser, collimating lens, thermal control, and driver circuit is described. Three such modules are used in an optical transmitter designed for use in NASA space laser communications experiments. Details of the various components are discussed, as well as laser diode lifetest results.

Holcomb, Terry L.↗
NASA NTRS1989

NASA direct detection laser diode driver

TRW has developed a prototype driver circuit for GaAs laser diodes as part of the NASA/Goddard Space Flight Center's Direct Detection Laser Transceiver (DDLT) program. The circuit is designed to drive the laser diode over a range of user-selectable data rates from 1.7 to 220 Mbps, Manchester-encoded, while ensuring compatibility with 8-bit and quaternary pulse position modulation (QPPM) formats for simulating deep space communications. The resulting hybrid circuit has demonstrated 10 to 90 percent rise and fall times of less than 300 ps at peak currents exceeding 100 mA.

Seery, B. D.↗
NASA NTRS1990

Electrooptic modulation methods for high sensitivity tunable diode laser spectroscopy

A CdTe phase modulator and low power RF sources have been used with Pb-salt tunable diode lasers operating near 8 microns to generate optical sidebands for high sensitivity absorption spectroscopy. Sweep averaged, first-derivative sample spectra of CH4 were acquired by wideband phase sensitive detection of the electrooptically (EO) generated carrier-sideband beat signal. EO generated beat signals were also used to frequency lock the TDL to spectral lines. This eliminates low frequency diode jitter, and avoids the excess laser linewidth broadening that accompanies TDL current modulation frequency locking methods.

Glenar, David A.↗
NASA NTRS1990

Millimeter-wave detection using resonant tunnelling diodes

A lattice-matched InGaAs/InAlAs resonant tunnelling diode is studied as a video detector in the millimeter-wave range. Tangential signal sensitivity and video resistance measurements are made as a function of bias and frequency. A tangential signal sensitivity of -37 dBm (1 MHz amplifier bandwidth) with a corresponding video resistance of 350 ohms at 40 GHz has been measured. These results appear to be the first millimeter-wave tangential signal sensitivity and video resistance results for a resonant tunnelling diode.

Mehdi, I.↗
NASA NTRS1991

Low-Loss Coupler For Microwave Laser-Diode Modulation

Elimination of series resistor reduces loss of radio-frequency power. Quarter-wavelength matching section connected to transmission line eliminates need for resistor near laser diode and extends frequency response of system. Concept significantly extends relatively flat frequency response of laser diode or similar component, while simplifying design of its package, increasing amplitude of output signal, and reducing dissipation of heat by eliminating resistance. Phase characteristics approximately linear and any digital information transmitted not significantly altered.

Toda, Minoru↗
NASA NTRS1991

Improved Planar Schottky Diode

Modifications of design and fabrication of surface-channel planar Schottky diode (GSC-13063) reduce parasitic capacitances to theoretical minimum, eliminate buried layer of conductive material between anode contact and semi-insulating substrate, and reduce thickness of diode chip. Changes in epitaxial layer structure and additional fabrication steps reduce conversion loss in millimeter and submillimeter mixers.

Bishop, William↗
NASA NTRS1991

Computer Processing Of Tunable-Diode-Laser Spectra

Tunable-diode-laser spectrometer measuring transmission spectrum of gas operates under control of computer, which also processes measurement data. Measurements in three channels processed into spectra. Computer controls current supplied to tunable diode laser, stepping it through small increments of wavelength while processing spectral measurements at each step. Program includes library of routines for general manipulation and plotting of spectra, least-squares fitting of direct-transmission and harmonic-absorption spectra, and deconvolution for determination of laser linewidth and for removal of instrumental broadening of spectral lines.

May, Randy D.↗
NASA NTRS1991

Self-Injection Locking Of Diode Lasers

Simple optical coupling scheme locks array of gain-guided diode lasers into oscillation in single mode and with single-lobed output beam. Selective feedback from thin etalon self-injection-locks array into desired mode. One application of new scheme for pumping of neodymium: yttrium aluminum garnet lasers with diode-laser arrays.

Hemmati, H.↗
NASA NTRS1991

Stirling-Cycle Cooling For Tunable Diode Laser

Miniature Stirling-cycle cooler effective in continously cooling PbSnTe tunable diode laser to stable operating temperature near 80 K. Simplifies laboratory diode-laser spectroscopy and instruments for use aboard aircraft and balloons.

Durso, Santo S.↗
NASA NTRS1991

Integral bypass diodes in an amorphous silicon alloy photovoltaic module

Thin-film, tandem-junction, amorphous silicon (a-Si) photovoltaic modules were constructed in which a part of the a-Si alloy cell material is used to form bypass protection diodes. This integral design circumvents the need for incorporating external, conventional diodes, thus simplifying the manufacturing process and reducing module weight.

Hanak, J. J.↗
NASA NTRS1990

Fabrication of IrSi(3)/p-Si Schottky diodes by a molecular beam epitaxy technique

IrSi(3)/p-Si Schottky diodes have been fabricated by a molecular beam epitaxy technique at 630 C. Good surface morphology was observed for IrSi(3) layers grown at temperatures below 680 C, and an increasing tendency to form islands is observed in samples grown at higher temperatures. Good diode current-voltage characteristics were observed and Schottky barrier heights of 0.14-0.18 eV were determined by activation energy analysis and spectral response measurement.

Lin, T. L.↗
NASA NTRS1990

Single-frequency diode-pumped lasers for free-space optical communication

Recent advances in laser technology for intersatellite optical communication systems are reviewed and illustrated with graphs and diagrams. Topics addressed include (1) single-frequency diode-pumped Nd:YAG lasers of monolithic ring configuration (yielding 368-384 mW output power with 1-W pumping), (2) injection chaining of up to 10 monolithic resonators to achieve redundancy and/or higher output power, (3) 2-kHz-linewidth 5-mW versions of (1) which are tunable over a 30-MHz range for use as local oscillators in coherent communication, (4) resonant external modulation and doubling or resonant phase modulation of diode-pumped lasers, and (5) wavelength multiplexing.

Kane, Thomas J.↗
NASA NTRS1991

Oscillations up to 712 GHz in InAs/AlSb resonant-tunneling diodes

Oscillations have been obtained at frequencies from 100 to 712 GHz in InAs/AlSb double-barrier resonant-tunneling diodes at room temperature. The measured power density at 360 GHz was 90 W/sq cm, which is 50 times that generated by GaAs/AlAs diodes at essentially the same frequency. The oscillation at 712 GHz represents the highest frequency reported to date from a solid-state electronic oscillator at room temperature.

Brown, E. R.↗
NASA NTRS1991

Scalable diode array pumped Nd rod laser

Experiments were carried out on a five-array pump head which utilizes gold-coated reflective cones to couple the pump energy to Nd:YAG and Nd:YLF rod lasers, demonstrating high efficiency and uniform energy deposition. Because the cones function as optical diodes to light outside their acceptance angle (typically 10-15 deg), much of the diode energy not absorbed on the first pass can be returned to the rod.

Zenzie, H. H.↗
NASA NTRS1990

The effect of neutron irradiation on the properties of AlGaAs/GaAs laser diodes

The effects of neutron irradiation on several properties of both single and multiple stripe laser diodes have been examined. Prior to fast neutron irradiation, total light output as a function of laser current, threshold current, near-field pattern, far-field pattern, and laser output wavelength spectra were measured at room temperature. These measurements were then repeated at intermittent neutron fluence levels. It was observed that the threshold current increased with neutron fluence for all devices examined. In contrast, neutron irradiation had only an indirect effect on the remainder of the laser diode properties in that the higher currents required for operation after irradiation caused variations in these properties.

Barnes, C. E.↗