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Results for “OPTICAL REFLECTIVITY”

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 127 records · Page 7
All sourcesNASA NTRSDOE OSTI
NASA NTRS1988

Space infrared telescope facility wide field and diffraction limited array camera (IRAC)

The wide-field and diffraction limited array camera (IRAC) is capable of two-dimensional photometry in either a wide-field or diffraction-limited mode over the wavelength range from 2 to 30 microns with a possible extension to 120 microns. A low-doped indium antimonide detector was developed for 1.8 to 5.0 microns, detectors were tested and optimized for the entire 1.8 to 30 micron range, beamsplitters were developed and tested for the 1.8 to 30 micron range, and tradeoff studies of the camera's optical system performed. Data are presented on the performance of InSb, Si:In, Si:Ga, and Si:Sb array detectors bumpbonded to a multiplexed CMOS readout chip of the source-follower type at SIRTF operating backgrounds (equal to or less than 1 x 10 to the 8th ph/sq cm/sec) and temperature (4 to 12 K). Some results at higher temperatures are also presented for comparison to SIRTF temperature results. Data are also presented on the performance of IRAC beamsplitters at room temperature at both 0 and 45 deg angle of incidence and on the performance of the all-reflecting optical system baselined for the camera.

Fazio, Giovanni G.↗
NASA NTRS1994

Optical and Electrical Properties of Reactively Sputtered TiN, ZrN, and HfN Thin Films

Thin films of titanium, zirconium, and hafnium nitride are prepared by DC magnetron reactive sputtering at room temperature on fused silica, optical glass, and silicon substrates. Deposition parameters are investigated in order to obtain stoichiometric films. The optical and electrical properties of the films as a function of nitrogen partial pressure are determined. The results show that an inverse correlation exists between the optical reflectance and the electrical resistivity of the films. Ellipsometer data for all three films show that their refractive index in the visible spectrum is decreased by increasing the film thickness while the extinction coefficient is unchanged. Thin films of TiN have the lowest room temperature resistivity relative to ZrN and HfN thin films.

Reactive↗
NASA NTRS2020

Optical Design of the EXperiment for Cryogenic Large-Aperture Intensity Mapping (EXCLAIM)

This work describes the optical design of the EXperiment for Cryogenic Large-Aperture Intensity Mapping(EXCLAIM). EXCLAIM is a balloon-borne telescope that will measure integrated line emission from carbonmonoxide (CO) at redshiftsz <1 and ionized carbon ([CII]) at redshiftsz= 2.5−3.5 to probe star forma-tion over cosmic time in cross-correlation with galaxy redshift surveys. The EXCLAIM instrument will observeat frequencies of 420–540 GHz using six microfabricated silicon integrated spectrometers with spectral resolv-ing powerR= 512 coupled to kinetic inductance detectors (KIDs). A completely cryogenic telescope cooledto a temperature below 5 K provides low-background observations between narrow atmospheric lines in thestratosphere. Off-axis reflective optics use a 90-cm primary mirror to provide 4.2′full-width at half-maximum(FWHM) resolution at the center of the EXCLAIM band over a field of view of 22.5′. Illumination of the 1.7 Kcold stop combined with blackened baffling at multiple places in the optical system ensures low (<−40 dB) edgeillumination of the primary to minimize spill onto warmer elements at the top of the dewar.

Thomas Essinger-Hileman↗
NASA NTRS1970

Ion implantation damage effects in silicon

Ion implantation lattice damage effects in crystalline silicon with allowance for optical reflectivity, considering annealing temperature and amorphous layer formation

Eberle, D. E.↗
NASA NTRS1971

Measurement of lattice damage caused by ion-implantation doping of semiconductors.

Discussion of two new techniques used to measure the lattice damage produced in GaAs by the implantation of 60 keV cadmium ions. In the first method, optical reflection spectra of the ion-implanted samples were measured in the wavelength range from 2000 to 4600 A. The decrease in reflectivity resulting from ion-implantation was used to determine the relative amount of lattice damage as a function of ion dose. The second technique employed the scanning electron microscope. Patterns very similar in appearance to Kikuchi electron diffraction patterns are obtained when the secondary and/or backscattered electron intensity is displayed as a function of the angle of incidence of the electron beam on a single crystal surface. The results of measurements made by both methods are compared with each other and with data obtained by the method of measuring lattice damage by Rutherford scattering of 1 MeV helium ions.

Hunsperger, R. G.↗
NASA NTRS1973

Broadband ultraviolet reflectance filters for space applications.

It is shown that a simple metal-dielectric-metal filter for broadband ultraviolet (BUV) reflectance control can provide a stable and effective means for reducing stray visible radiation in UV reflective optical systems. The application of such a filter in a BUV instrument resulted in a reduction of scattered visible light by at least an order of magnitude. The instrument has been in orbit for 2.5 year without loss of sensitivity or an increase in scattered light background.-

Osantowski, J. F.↗
NASA NTRS1975

V-grooved silicon solar cells

Silicon solar cells with macroscopic V-shaped grooves and microscopically texturized surfaces were made by preferential etching techniques. Various conditions for potassium hydroxide and hydrazine hydrate etching were investigated. Optical reflection losses from these surface were reduced. The reduced reflection occurred at all wavelengths and resulted in improved short circuit current and spectral response. Improved collection efficiency is also expected from this structure due to generation of carriers closer to the cell junction. Microscopic point measurements of collected current using a scanning electron microscope showed that current collected at the peaks of the texturized surface were only 80 percent of those collected in the valleys.

Baraona, C. R.↗
NASA NTRS1975

V-grooved silicon solar cells

Silicon solar cells with macroscopic V-shaped grooves and microscopically texturized surfaces have been made by preferential etching techniques. Various conditions for potassium hydroxide and hydrazine hydrate etching were investigated. Optical reflection losses from these surface were reduced. The reduced reflection occurred at all wavelengths and resulted in improved short circuit current and spectral response. Improved collection efficiency is also expected from this structure due to generation of carriers closer to the cell junction. Microscopic point measurements of collected current using a scanning electron microscope showed that current collected at the peaks of the texturized surface were only 80% of those collected in the valleys.

Baraona, C. R.↗
NASA NTRS1975

Laser space rendezvous and docking system trade-off study

The use, design, and fabrication feasibility of scanning the laser beam by swiveling the outside mirror with a ball joint swivel system is examined along with the applicability of graphite reinforced epoxy material for the construction of reflective optics. It is indicated that (1) the cost of graphite-epoxy will be more than that of many other materials due to the amount of special tooling required; (2) the weight advantage of graphite-epoxy over beryllium is minimal; the ball joint swivel system is accurate enough to perform the scanning function; and that the ball joint will result in a simpler and more cost effective scanning mechanism.

Adelman, S.↗
NASA NTRS1976

Cooled infrared telescope development

The feasibility of the design concept for a 1-m-aperture, cryogenically cooled telescope for Spacelab is assessed. The device makes use of double-folded Gregorian reflective optics. The planned cryogen is helium, and beryllium will be used for the 1.2 m primary mirror. Results of studies based on smaller instruments indicate that no new technology will be required to construct a Shuttle Infrared Telescope Facility which will offer improvement over the sensitivity of conventional telescopes by a factor of 1000 at 10 micrometers.

Young, L. S.↗
NASA NTRS1977

Electrical, magnetic, and optical properties of the tetrathiafulvalene /TTF/ pseudohalides, /TTF/12/SCN/7 and /TTF/12/SeCN/7

The electrical, magnetic, and optical properties of charge-transfer salts containing tetrathiafulvalene (TTF) and the pseudohalides, thiocyanate (SCN) and selenocyanate (SeCN), have been investigated. These salts are quasi-one-dimensional compounds containing cation radicals only, in contrast to a cation-radical-anion-radical system, such as tetrathiafulvalene tetracyanoquinodimethane (TTF) (TCNQ). Measurements of electrical conductivity, thermoelectric power, and optical reflectivity of single crystals of the nonstoichiometric salts (TTF)12(SCN)7 and (TTF)12(SeCN)7 show metal-like characteristics above 200 K (high-temperature region). The conductivities at room temperature are approximately 750 mho/cm comparable to those found in (TTF) (TCNQ), and increase with decreasing temperature down to approximately 200 K. The thermoelectric power at room temperature is small and positive (approximately 9 microvolts/deg K), and decreases linearly with decreasing temperature in this region (as expected for metal-like hole conduction along the TTF chains). The ESR intensity, however, decreases with decreasing temperature above 200 K. At 170 K a metal-nonmetal transition occurs, and the transport and magnetic properties below this temperature are characteristic of a semiconducting state.

Somoano, R. B.↗
NASA NTRS1980

Large-volume multiple-path nuclear-pumped laser

Output of nuclear pumped laser is increased using mirrors, so multiple optical reflections enlarge lasing-mode volume. Design requires comparatively low thermal neutron flux, uses flux more efficiently. Flux for lasing approaches that available from steady-state reactor. Outputs over 100 watts have been reached.

Hohl, F.↗
NASA NTRS1980

Absolute line strengths in nu4, /C-12/H4 - A dual-beam diode laser spectrometer with sweep integration

A tunable diode laser spectrometer with several unique features has been developed for use in the middle IR. The all-reflective optical system has a dual-beam configuration before the dispersive mode selector to eliminate transit-angle errors at the calibration etalon. By maintaining separated beams through the mode selector, beam combiner losses are avoided. Averaging successive sweeps of the current-modulated laser permits stable reproducible spectral integrations, eliminating etalon thermal errors and producing high photometric sensitivity. Line strengths have been measured using this instrument for eleven transitions in nu4 of (C-12)H4. These include R0 and R1 and nine P-branch transitions in the 1202-1263-per cm range. Techniques for measuring strengths with a diode laser are discussed.

Jennings, D. E.↗
NASA NTRS1981

Study of the effects of impurities on the properties of silicon materials and performance of silicon solar cell

The effect of silicon film thickness on the energy conversion efficiency of a back surface field solar cell is investigated. A computer-aided design study on the dependence of efficiency peaks on the concentrations of the recombination and dopant impurities is presented. The illuminated current voltage characteristics of over 100 cell designs were obtained using the transmission line circuit model to numerically solve the Shockley Equations. Using an AM1 efficiency of 17% as a target value, it is shown that the efficiency versus thickness dependence has a broad maximum which varies less than 1% over more than three-to-one range of cell thickness from 30 to 100 microns. Optical reflecting back surface will give only a slight improvement of AM1 efficiency, about 0.7%, in this thickness range. The sensitive dependence of efficiency on patchiness across the back surface field, low high junction in thin cells is noted.

Sah, C. T.↗
NASA NTRS1980

A 10 micron heterodyne receiver for ultra high resolution astronomical spectroscopy

An improved CO2 laser heterodyne spectrometer is examined. The present system uses reflective optics to eliminate refocusing at different wavelengths, and the local oscillator is a line-center-stabilized isotopic CO2 laser. A tunable diffraction grating makes possible easy and rapid selection of over 50 transitions per isotope of CO2. The IF (0 to 1.6 GHz) from the HgCdTe photomizer is analyzed by a 128-channel filter bank, consisting of 64 tunable 5-MHz filters and 64 fixed 25-MHz RF filters. These filters provide resolving powers of about 1,000,000 to 10,000,000 and velocity resolution of 50 to 250 m/sec; their output is synchronously detected, integrated, multiplexed and stored in a buffer memory for the desired integration period. Kitt Peak observations show the wide spectral coverage, wide mixer and electronics bandwidth, and high sensitivity of the system.

Buhl, D.↗
NASA NTRS1982

EUV spectroscopic plasma diagnostics for the solar wind acceleration region

Possibilities are considered for probing physical conditions in the solar corona with strong EUV resonance lines from ions such as N V, O VI, Ne VIII, Mg X, and Si XII. Through measurements of the intensities and profiles of EUV spectral lines with coronagraphic instrumentation employing normal incidence reflecting optics, it is possible to acquire information on electron, proton, and ion temperatures and velocity distributions; electron, H I, and ion densities; mass flow and nonthermal velocities; and chemical abundances. This information will provide critical empirical constraints on physical processes responsible for plasma heating, solar wind acceleration, and transport of mass, momentum, and energy in the solar corona, as well as providing constraints on theoretical models for solar and stellar coronae and mass loss.

Kohl, J. L.↗