Buffer gases to increase the efficiency of an optically pumped far infrared D2O laser

The effects of buffer gas additives on the performance of an optically pumped D2O laser operating at 385 microns have been investigated both experimentally and by numerical simulation. Three gases, sulfur hexafluoride, carbon tetrafluoride, and n-hexane, were found to produce an increase of up to 40 percent in the pumping efficiency, as well as significant lengthening of the far infrared pulse. Under optimum conditions, 2.6 J in a 1 micron long pulse have been obtained. The buffer gases are shown to eliminate the vibrational deexcitation bottleneck, which in pure D2O leads to an accumulation of population in the upper vibrational level and, hence, a reduction in the efficiency of absorption of the pump beam.