In addition to general technology development, we are also involved in applying our technology to a variety of areas. We highlight one of them here, Lidar:
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Much of the technology developed at Q-Peak has been supported by customers whose eventual application is lidar. There are four general areas of application, hard-target, aerosol, DIAL and Doppler.
Hard target
Using a laser to transmit energy in order to detect reflections from "hard" targets, such as the ground, trees or aircraft is sometimes referred to as ladar, instead of lidar. Recently, some of the diode-pumped solid state laser technology developed at Q-Peak has been applied to ladar, for applications to smart weapons systems.
Aerosol
Natural (e.g. dust, pollen, salt spray) or man-made aerosols (e.g. soot, ash) in the atmosphere scatter light; lasers of sufficiently high power can be used with appropriate receivers and signal-processing systems to detect the presence of aerosols and provide some degree of information on their density. With short-pulse lasers employed as transmitters the aerosol concentration as a function of range can be determined, providing a measurement capability unavailable with other techniques.
Q-Peak has pioneered in the use of high-energy, Nd-laser pumped parametric oscillators (OPOs) as eye-safe (1.5 um-wavelength) sources for aerosol lidar (NL1, click here for the complete paper). This technology has been tested in complete lidar systems through support from NASA Langley and a collaboration with Professor Dennis Killinger at the Center for Laser Atmospheric Studies, University of South Florida, where ranging from aerosols at distances up to 5 km has been accomplished (Li1, Li2). We have built a compact OPO source capable of 240 mJ/pulse at 1.55 um, with a 30-Hz pulse rate, for eventual use in the Los Alamos National Laboratory Miniature Lidar System. The device is shown as one version of the Compact Laser Head. Finally, the high-energy OPO was a key component of a multi-year program at Schwartz Electro-Optics to develop a lidar for long-range detection of aerosols, as part of the Army Edgewood Research and Development Center (ERDEC) LR-SBDS program. The aim of the program was to provide an early warning of the possible release of biological warfare agents.
DIAL
Differential absorption lidar, or DIAL, employs a laser source that can be tuned to coincide with absorption lines or bands of a gas. When used as a lidar source, the laser tuned to an absorption band of a particular gas will experience a reduction in return signal from aerosol scattering if there is any gas present in the laser beam path. By tuning the laser to another wavelength less strongly absorbed by the gas and comparing the on-line, off-line signals, (hence the term differential) one can develop data showing gas concentration as a function of range. As with aerosol lidar, DIAL provides a unique measurement function, range-resolved measurements of atmospheric gas concentration. At short wavelengths DIAL can rely on Rayleigh scattering from air molecules, rather than aerosols, and thus function independently of aerosol concentrations.
DIAL technology requires the use of tunable, precise-wavelength-control lasers and/or parametric oscillators, a major area of expertise at Q-Peak. Prior support for DIAL sources has come through a NASA Langley, three-year, $1.1 million program, mentioned above, to develop high-energy Ti:sapphire lasers and subsequent support by ONR/DARPA to develop harmonic generation techniques for Ti:sapphire lasers to be used in submarine communications. In another area of DIAL transmitters, we developed the first room-temperature Co:MgF2 tunable infrared solid state laser as a source for the 1750-2500-nm wavelength region, under NASA SBIR funding. Current support for DIAL or DIAL-related technology includes development of ruggedized Ti:sapphire lasers for airborne applications, narrow-linewidth, injection-seeded Ti:sapphire lasers for wind-tunnel diagnostics, Ti:sapphire lasers combined with harmonic generation for coverage of the 250-310-nm wavelength region and tunable OPOs for mid-IR DIAL systems.
Doppler
Light scattered from hard targets, aerosols or molecules is shifted slightly in wavelength by the Doppler effect if the scattering entity has any velocity component along the direction of the laser beam. By using single-frequency transmitters and coherent receivers, Doppler lidar systems can provide range-resolved data on wind velocity as a function of distance from the lidar system by virtue of aerosol or molecular scattering. In the area of coherent lidar, we first developed a rapidly tunable (50 GHz in 5 msec), single-frequency, diode-pumped Nd:YAG laser for use as the master oscillator in a mid-course-discrimination, coherent lidar system for SDIO. Q-Peak was supported for a number of years by the Air Force Geophysics Directorate through two Phase II SBIR programs and related contracts to develop technology for 2-um-wavelength Doppler lidar systems applied to wind sensing (Li3, Li4). Also, this area was supported by a program with ARPA/NASA Marshall to build a pulsed, diode-pumped, 2-um transmitter, coherent receiver and Doppler signal processing system and a commercial contract to build a rugged, single-frequency, cw 2-um laser with an output power of 1 Watt.
Lidar
Li2. S.R. Harrell, W. Wilcox, D. Killinger, G.A. Rines and R.A. Schwarz, "Atmospheric Lidar using High-Energy 1.57 Micron Optical Parametric Oscillator," in 7th Topical Meeting on Optical Remote Sensing of the Atmosphere, (Optical Society of America, Washington, DC 1995), Paper MC3.
Li3. P.F. Moulton, J. Harrison, J.H. Flint and D.M. Rines "Solid State Lasers for Coherent Laser Radar", in Technical Digest on Coherent Laser Radar: Technology and Applications, 1991 (Optical Society of America, Washington, DC 1991) Vol. 12, pp. 95-96.
Li4. R.J. Martinsen, A. Jankevics, C. Plum, and J. Flint, "Clear Air Turbulence Detection with a 2 µm Lidar Employing Velocity-Width Processing,", 6th Topical Meeting on Optical Remote Sensing of the Atmosphere, (Optical Society of America, Washington, DC 1993).
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