HYDROGEN-FLUORIDE CHEMICAL-LASER MULTIPLE-PASS AMPLIFIER PERFORMANCE

The performance of a continuous wave hydrogen fluoride chemical laser master oscillator with power amplifier was measured as a function of i nput power, the number of passes through the gain medium, and location of the optical axis of the input beam. The amplification ratio is an inverse function of the input power (intensity) and, for maximum ampli fication, the peak of the intensity distribution must be matched to th at of the zero power gain distribution in the amplifier. A substantial performance advantage was measured with two-pass amplification when t he two passes overlapped at least 60% and filled less than 84% of the zero power gain zone of the amplifier. The measured two-pass P-out vs P-in performance curve was significantly above the single pass data an d showed that only one-sixth of a device's oscillator output must be i nput to obtain two-pass amplifier output equal to the device's oscilla tor performance. An amplifier performance model that predicts a device 's amplifier perfor mance given the device's oscillator performance as a function of reflectivity was extended to predict multiple-pass ampl ifier performance. The two pass model predictions were in good agreeme nt with the measured two-pass amplifier performance data. The predicte d amplifier performance as a function of gain length was found to be i ndependent of device and showed that, with a 1-m gain length, one osci llator may be able to drive as many as 12 two pass amplifiers.