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  • 1
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    Tunable frequency stabilized diode-laser-pumped Tm,Ho:YLiF4 laser at room temperature (1993)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: A diode-laser-pumped single-frequency thulium holmium yttrium lithium fluoride laser that exhibits a closed-loop stability of a few megahertz and a continuous single-mode tuning range of 800 MHz is described. The laser output power is 25 mW, and is tunable over about 8/cm at 25 C.
    Keywords: LASERS AND MASERS
    Type: Applied Optics (ISSN 0003-6935); 32; 12; p. 2082-2084.
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  • 2
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    Infrared lidars for atmospheric remote sensing (1991)
    In:  Other Sources
    Details
    Publication Date: 2011-08-24
    Description: Lidars using pulsed TEA-CO2 transmitters and coherent receivers have been developed at JPL and used to measure atmospheric backscatter and extinction at wavelengths in the 9-11 micron region. The global winds measurement application of coherent Doppler lidar requires intensive study of the global climatology of aerosol and cloud backscatter and extinction. An airborne lidar was recently flown on the NASA DC-8 research aircraft for operation during two Pacific circumnavigation missions. The instrument characteristics, as well as representative measurement results, are discussed.
    Keywords: LASERS AND MASERS
    Type: In: Infrared technology XVII; Proceedings of the Meeting, San Diego, CA, July 22-26, 1991 (A93-38376 15-35); p. 160-163.
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  • 3
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    Efficient CW diode-pumped Tm, Ho:YLF laser with tunability near 2.067 microns (1992)
    In:  Other Sources
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    Publication Date: 2011-08-24
    Description: A conversion efficiency of 42 percent and slope efficiency of approximately 60 percent relative to absorbed pump power are reported from a continuous wave diode-pumped Tm, Ho:YLF laser at 2 microns with output power of 84 mW at sub-ambient temperatures. The emission spectrum is etalon tunable over a range of 16/cm centered on 2.067 microns, with fine tuning capability of the transition frequency with crystal temperature at a measured rate of about -0.03/cm-K. The effective emission cross section is measured to be 5 x 10 exp -21 sq cm. These and other aspects of the laser performance are discussed in the context of calculated atmospheric absorption characteristics in this spectral region and potential use in remote sensing applications.
    Keywords: LASERS AND MASERS
    Type: IEEE Journal of Quantum Electronics (ISSN 0018-9197); 28; 4, Ap
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  • 4
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    Automated rejection of parasitic frequency sidebands in heterodyne-detection LIDAR applications (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: A technique is described for the detection of the sporadic onset of multiaxial mode behavior of a normally single-mode TEA CO2 laser. The technique is implemented using primarily commercial circuit modules; it incorporates a peak detector that displays the RF detector output on a digital voltmeter, and a LED bar graph. The technique was successfully demonstrated with an existing coherent atmospheric LIDAR facility utilizing an injection-seeded single-mode TEA CO2 laser. The block schematic diagram is included.
    Keywords: LASERS AND MASERS
    Type: Review of Scientific Instruments (ISSN 0034-6748); 60; 78-81
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  • 5
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    Atmospheric correlation-time measurements and effects on coherent Doppler lidar (1987)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The time for which the backscatter from an ensemble of atmospheric aerosol particles remains coherent was studied by using a pulsed TEA CO2 lidar with coherent detection. Experimental results are compared with predictions by using model pulse shapes appropriate for TEA CO2 laser transmitters. The correlation time of the backscatter return signal is important in studies of atmospheric turbulence and its effects on optical propagation and backscatter. Techniques for its measurement are discussed and evaluated.
    Keywords: LASERS AND MASERS
    Type: Optical Society of America, Journal, A: Optics and Image Science (ISSN 0740-3232); 4; 367-373
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  • 6
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    Unstable resonator antenna properties in coherent lidar applications - A comparative study (1988)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The antenna parameters of a coherent lidar in the far-field diffraction-limited regime, where the lidar transmitter consists of an unstable resonator with a Gaussian reflectivity profile output coupler, are investigated. A figure-of-merit combining lasr transmitter energy extraction efficiency with the far-field attributes of a given cavity configuration has been used to compare the lidar performance and relative merits of such systems as they relate to those of conventional unstable cavities with diffractive output coupling.
    Keywords: LASERS AND MASERS
    Type: Applied Optics (ISSN 0003-6935); 27; 3645-364
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  • 7
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    Frequency stabilization in injection controlled pulsed CO2 lasers (1987)
    In:  CASI
    Details
    Publication Date: 2013-08-31
    Description: Longitudinal mode selection by injection has been demonstrated as a viable technique for tailoring a TEA-CO2 laser with pulse energies of a Joule or greater to fit the requirements of a coherent lidar transmitter. Once reliable generation of single-longitudinal-mode (SLM) pulses is obtained, one can study the intrapulse frequency variation and attempt to determine the sources of frequency sweeping, or chirp. These sources include the effect of the decaying plasma, the thermal gradient due to the energy dissipation associated with the laser mechanism itself, and the pressure shift of the center frequency of the laser transition. The use of the positive-branch unstable resonator as an efficient means of coupling a discharge with transverse spatial dimensions of the order of centimeters to an optical cavity mode introduces another concern: namely, what can be done to emphasize transverse mode discrimination in an unstable resonator cavity while maintaining high coupling efficiency. These issues are briefly discussed in the paper, and representative experimental examples are included.
    Keywords: LASERS AND MASERS
    Type: NASA. Langley Research Center Closed-Cycle, Frequency-Stable CO2 Laser Technology; p 55-63
    Format: application/pdf
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  • 8
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    Coherent Doppler lidar for measurements of wind fields (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: The signal-processing techniques for obtaining the velocity estimates and the fundamental factors that influence coherent lidar performance are considered. The similarities and distinctions between Doppler lidar and Doppler radars are discussed. The capability of coherent Doppler lidars for mapping wind fields over selected regions in the lower atmosphere and greatly enhancing the capability to visualize flow patterns in real time is discussed, and examples are given. Salient features of a concept for an earth-orbiting Doppler lidar to be launched in the late 1990s are examined.
    Keywords: LASERS AND MASERS
    Type: IEEE, Proceedings (ISSN 0018-9219); 77; 449-462
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  • 9
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    Reflectance characteristics of reference materials used in lidar hard target calibration (1989)
    In:  Other Sources
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    Publication Date: 2011-08-19
    Description: Lidar hard target calibration is discussed, emphasizing the transfer target methodology. Characteristics of example calibratrion target surfaces are described in light of four reflectance mechanisms, specular, diffuse, retroreflection, and off-specular reflectance. The ideal transfer target is one which can be described as entirely diffusely reflecting, i.e., Lambertian. Correction for retroreflection is required when using the flowers of a sulfur transfer target at CO2 laser wavelengths. Corrections for specular and retroreflection for the integrating sphere are negligible; however, the off-specular reflectance of rough metal surfaces used in the integrating spheres is only qualitatively compared with the diffuse reflectance of flowers of sulfur.
    Keywords: LASERS AND MASERS
    Type: Applied Optics (ISSN 0003-6935); 28; 857-864
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  • 10
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    Tunable CW diode-pumped Tm,Ho:YLiF4 laser operating at or near room temperature (1995)
    In:  CASI
    Details
    Publication Date: 2019-06-28
    Description: A conversion efficiency of 42% and slope efficiency of 60% relative to absorbed pump power are obtained from a continuous wave diode-pumped Tm,Ho:YLiF4 laser at 2 microns with output power of 84 mW at a crystal temperature of 275 K. The emission spectrum is etalon tunable over a range of7 nm (16.3/cm) centered on 2.067 microns with fine tuning capability of the transition frequency with crystal temperature at a measured rate of -0.03/(cm)K. The effective emission cross-section is measured to be 5 x 10(exp -21) cm squared. These and other aspects of the laser performance are disclosed in the context of calculated atmospheric absorption characteristics in this spectral region and potential use in remote sensing applications. Single frequency output and frequency stabilization are achieved using an intracavity etalon in conjunction with an external reference etalon.
    Keywords: LASERS AND MASERS
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