CO2 OPTICAL RADAR SYSTEM
Semiannual technical summary rept. 1 Nov 1966-1 May 1967
HUGHES RESEARCH LABS MALIBU CA
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Progress is reported on a program to develop and build a 1 kW average power 10.6 micron amplifier for radar applications. Small signal gain and saturation measurements were made on 1-in. diameter amplifier tubes using a CO2- N2-He mixture with cw driving signals. Optimum values for cw discharge tubes were 3 dBm and 60 to 90 Wsq cm for pulsed discharges at 500 pps, they were 4 dBm and more than 200 Wsq cm. Based on the above values, transmitter designs were made using pulsed operation or a combination of pulsed and cw operation at different stages. The most promising of these designs would use 1 a 10 W cw oscillator, 2 a folded 16 m, 1 in. diameter tube, 3 a mechanical modulator with recollimating optics, and 4 a final amplifier of 8 m, 2 in. diameter tubes operated with a pulsed discharge. The device would be 32 ft long, including folding and recollimating optics. The mechanisms of the CO2-N2-He laser are summarized and relevant rates and coefficients tabulated. The theory of gain saturation is reviewed and equations derived. Numerical values for small signal gain and saturation flux are calculated and compared with experimental values. Collisional cross relaxation among rotational levels appears to be important, and a method of treating it is presented. The gain saturation equation for simplified cases is solved. Diffraction beam spreading effects on amplifier performance are discussed, and a solution for the effect of gain saturation on the radial beam profile is given.
- Optical Detection and Detectors