Gain and relaxation studies in transversely excited HF lasers

The results of measurements of the spatial and temporal dependence of the gain of a pulsed HF laser are reported and are compared with those for CO2lasers. While the propagation in space of a locally excited gain medium is observed to be comparable for the two lasers, the time developments are vastly different. The extremely fast gain decay rates that were observed in the HF laser are shown to be a serious detriment to efficient high-power CW or long-pulse operation. Short pulse HF lasers, however, can be operated relatively efficiently at high energies. This was demonstrated by obtaining 350-mJ pulses from a 75-cm "pin" laser excited by 50-ns pulses from a Marx bank.