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  • 1
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    Single heterostructure lasers of PbS/1-x/Se/x/ and Pb/1-x/Sn/x/Se with wide tunability (1977)
    In:  Other Sources
    Details
    Publication Date: 2011-08-17
    Description: Single-heterostructure diode lasers formed by compositional interdiffusion (CID) and liquid-phase epitaxy (LPE) of lead salts are discussed. The CID technique, which involves creation of a single heterostructure in a pseudobinary compound having binary constituents with different vapor pressures, is reviewed; growth of lead-salt crystals of various compositions is described. Some electrical and optical characteristics, including properties indicative of high internal quantum efficiencies, are given for lasers which employ the CID and LPE diodes. High operating temperatures (i.e., liquid nitrogen levels and above), together with wide tuning ranges (a diode wavelength of 12.7 microns is reported), make the lasers useful in high-resolution spectrometry and advanced trace-gas monitoring systems.
    Keywords: LASERS AND MASERS
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  • 2
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    Rotationally resolved collisional transfer rates in OH (1986)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Fluorescence lidar measurements of the hydroxyl radical require detailed information concerning collision induced processes in order to deduce the radical number density from a lidar return. The Goddard SFC OH lidar currently utilizes a broadband detector which precludes the necessity of fully understanding collisional redistribution of rotational energy within the excited state. Numerous advantages result however from the inclusion of a detector with a bandpass only slightly larger that the Doppler width of a rotational line. This however places more stringent requirements on the spectroscopy. Measurements were accordingly made of rotationally resolved quenching rates for collisions with O2, N2, and H2O. Rotational transfer rates were also measured for the same colliders. Quenching rates were measured using a Nd-YAG pumped Rh6G dye laser doubled into the UV. The OH lifetimes were measured as a function of pressure of quenching gas at total pressures of between 50 and 250 microns. Rotational transfer rates were measured by recording the emission spectrum on an intensified diode array and integrating over 10.000 laser shots.
    Keywords: LASERS AND MASERS
    Type: NASA. Langley Research Center 13th International Laser Radar Conference; 1 p
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  • 3
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    Design curves for double-heterojunction laser diodes (1977)
    In:  Other Sources
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    Publication Date: 2011-08-17
    Description: This paper reviews theoretical double-heterojunction laser design curves relating the structure with the transverse mode order able to propagate, the degree of radiation confinement to the active region, the maximum field intensity within the device, and the radiated beam shape. The curves presented are general and applicable to any double-heterojunction structure where the spacing of the heterojunctions and the refractive index in the relevant regions are known.
    Keywords: LASERS AND MASERS
    Type: RCA Review; 38; Dec. 197
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  • 4
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    STROZ LITE - Stratospheric Ozone Lidar Trailer Experiment (1991)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A mobile dual-wavelength differential absorption lidar capable of making precise measurements of stratospheric ozone between 20 and 45 km has been developed at the Goddard Space Flight Center as part of the international Network for the Detection of Stratospheric Change. The system is installed in a 46-ft trailer, which enables the instrument to act as a network transfer standard and to be set up at any location where power can be obtained. A description of the instrument is presented, along with a discussion of the data analysis. Some results from an intercomparison held at JPL's Table Mountain Observatory in California during October and November 1988 are also presented.
    Keywords: LASERS AND MASERS
    Type: Optical Engineering (ISSN 0091-3286); 30; 31-39
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  • 5
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    Reliability improvements in tunable Pb1-xSnxSe diode lasers (1980)
    In:  CASI
    Details
    Publication Date: 2016-06-07
    Description: Recent developments in the technology of Pb-salt diode lasers which have led to significant improvements in reliability and lifetime, and to improved operation at very long wavelengths are described. A combination of packaging and contacting-metallurgy improvements has led to diode lasers that are stable both in terms of temperature cycling and shelf-storage time. Lasers cycled over 500 times between 77 K and 300 K have exhibited no measurable changes in either electrical contact resistance or threshold current. Utilizing metallurgical contacting process, both lasers and experimental n-type and p-type bulk materials are shown to have electrical contact resistance values that are stable for shelf storage periods well in excess of one year. Problems and experiments which have led to devices with improved performance stability are discussed. Stable device configurations achieved for material compositions yielding lasers which operate continuously at wavelengths as long as 30.3 micrometers are described.
    Keywords: LASERS AND MASERS
    Type: NASA. Langley Res. Center Heterodyne Systems and Technol., Pt. 1; p 63-78
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  • 6
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    Advanced airborne DIAL system capabilities for ozone and multiwavelength aerosol measurements (1988)
    In:  Other Sources
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    Publication Date: 2019-01-25
    Keywords: LASERS AND MASERS
    Type: Optical Society of America, Topical Meeting on Laser and Optical Remote Sensing: Instrumentation and Techniques. Technical Digest Series, Volume 18; p 51-54
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  • 7
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    Mode characteristics of nonplanar double-heterojunction and large-optical-cavity laser structures (1982)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: Mode behavior of nonplanar double-heterojunction (DH) and large-optical-cavity (LOC) lasers is investigated using the effective index method to model the lateral field distribution. The thickness variations of various layers for the devices discussed are correlated with the growth characteristics of liquid-phase epitaxy over topographical features (channels, mesas) etched into the substrate. The effective dielectric profiles of constricted double-heterojunction (CDH)-LOC lasers show a strong influence on transverse mode operation: the fundamental transverse mode (i.e., in the plane perpendicular to the junction) may be laterally index-guided, while the first (high)-order mode is laterally index-antiguided. The analytical model developed uses a smoothly varying hyperbolic cosine distribution to characterize lateral index variations. The waveguide model is applied to several lasers to illustrate conditions necessary to convert leaky modes to trapped ones via the active-region gain distribution. Theoretical radiation patterns are calculated using model parameters, and matched to an experimental far-field pattern.
    Keywords: LASERS AND MASERS
    Type: IEEE Journal of Quantum Electronics; QE-18; June 198
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  • 8
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    Coupled-mode analysis of phase-locked injection laser arrays (1984)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: A coupled-mode analysis has been developed to describe the output of phase-locked injection laser arrays. It is shown that an array of emitters with weak coupling can only operate in a set of discrete modes determined by the number of and the spacing of the emitters. The interaction between emitters leads to a splitting of the common frequency of operation that can be estimated from the coupling strength. The coupled-mode analysis is compared to calculations based on simple diffraction theory. A consequence of the analysis is an explanation for the commonly observed discrepancy between experimentally observed far-field lobe widths and those predicted by simple diffraction theory.
    Keywords: LASERS AND MASERS
    Type: Applied Physics Letters (ISSN 0003-6951); 44; 293-295
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  • 9
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    Coupled-mode analysis of gain and wavelength oscillation characteristics of diode laser phased arrays (1985)
    In:  Other Sources
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    Publication Date: 2019-06-28
    Description: The lasing wavelengths and gain characteristics of the modes of phase-locked arrays of channel-substrate-planar (CSP) lasers are presented. The gain values for the array modes are determined from complex coupling coefficients calculated using the fields of neighboring elements of the array. The computations show that, for index guided lasers which have nearly planar phase fronts, the highest order array mode will be preferred. The 'in-phase' or fundamental mode, which produces only one major lobe in the far-field radiation pattern, has the lowest modal gain of all array modes. The modal gain differential between the highest order and fundamental modes is less than 10/cm for weak coupling between the elements.
    Keywords: LASERS AND MASERS
    Type: IEEE Journal of Quantum Electronics (ISSN 0018-9197); QE-21; 458-464
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  • 10
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    Advanced development of Pb-salt semiconductor lasers for the 8.0 to 15.0 micrometer spectral region (1977)
    In:  CASI
    Details
    Publication Date: 2019-06-27
    Description: The technology was studied for producing Pb-salt diode lasers for the 8-51 micron spectral region suitable for use as local oscillators in a passive Laser Heterodyne Spectrometer (LHS). Consideration was given to long range NASA plans for the utilization of the passive LHS in a space shuttle environment. The general approach was to further develop the method of compositional interdiffusion (CID) recently reported, and used successfully at shorter wavelength. This technology was shown to provide an effective and reproducible method of producing a single-heterostructure (SH) diode of either the heterojunction or single-sided configuration. Performance specifications were exceeded in several devices, with single-ended CW power outputs as high as 0.88 milliwatts in a mode being achieved. The majority of the CID lasers fabricated had CW operating temperatures of over 60K; 30% of them operated CW above the boiling temperature of liquid nitrogen. CW operation above liquid nitrogen temperature was possible for wavelengths as long as 10.3 microns. Operation at 77K is significant with respect to space shuttle operations since its allows considerable simplification of cooling method.
    Keywords: LASERS AND MASERS
    Type: NASA-CR-145259
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