Laser radar component technology

doi:10.1109/5.482230

Laser radar component technology

1996-02-01

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DOI：10.1109/5.482230

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The implementation of laser radar systems has required significant advances in the technology of both transmitters and receivers. For a ground-based carbon dioxide (CO2) range-Doppler imaging radar it was necessary to develop (for the transmitters) ultrastable master oscillators and local oscillators, high-power amplifiers, frequency modulators, and isolators and (for the receivers) efficient, wide-bandwidth detectors. Extremely high spectral purity and short-term fractional frequency stabilities of Delta f/f(o) < 15 x 10(-13) have been routinely achieved with sealed-off ultrastable CW CO2 laser oscillators. Wideband amplifiers with pulse energies up to 100 J have been built for long-range measurements of space objects. InSb Faraday rotation isolators with >20 dB isolation and <1 dB insertion loss, and CdTe electrooptic frequency modulators producing 1-GHz linear frequency chirps in 1 mu s, are two additional key components that were implemented for the CO2 imaging radar transmitter chain. Lower-power CO2 laser transmitters were also developed for short-range portable or airborne radars. The utilization of solid state lasers as radar transmitters has increased in recent years, in part through the application of diode lasers as efficient pump sources, permitting the construction of compact radars, particularly for airborne or space-based systems. Frequency-doubled Nd:YAG lasers have been built and used in direct-detection short-pulse ranging radars for measurements on space objects. Ultracompact microchip diode-pumped laser transmitters are currently under development for lightweight inexpensive short-range imaging. Such transmitters have produced e-switched pulses as short as 115 ps, enabling range measurements with centimeter resolution. Eye-safety considerations have recently prompted work on solid state lasers at wavelengths longer than 1.4 mu m. Receiver development has included HgCdTe detectors with 50% heterodyne efficiency and several-gigahertz bandwidth for CO2 radars. For the shorter-wavelength solid state laser radars there have been recent significant advances in both photoemissive detectors and semiconductor avalanche photodiodes for sensitive direct detection at wavelengths up to 1.6 mu m.

Keywords:

SOLID-STATE LASERS

MU-M

PRESSURE SHIFTS

10.6 MU

CO2

PHOTODIODES

TRANSITIONS

FREQUENCIES

TI-AL2O3

Laser radar component technology

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