Hydrogen fluoride chemical laser multiple-pass amplifier performance

Abstract

The performance of a continuous wave hydrogen fluoride chemical laser master oscillator with power amplifier was measured as a function of input 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 amplification, the peak of the intensity distribution must be matched to that of the zero power gain distribution in the amplifier. A substantial performance advantage was measured with two-pass amplification when the two passes overlapped at least 60% and filled less than 84% of the zero power gain zone of the amplifier. The measured two-pass Pout vs P-m performance curve was significantly above the single-pass data and showed that only one-sixth of a device's oscillator output must be input to obtain two-pass amplifier output equal to the device's oscillator performance. An amplifier performance model that predicts a device's amplifier performance given the device's oscillator performance as a function of reflectivity was extended to predict multiplepass amplifier performance. The two-pass model predictions were in good agreement with the measured two-pass amplifier performance data. The predicted amplifier performance as a function of gain length was found to be independent of device and showed that, with a 1-m gain length, one oscillator may be able to drive as many as 12 two-pass amplifiers.