Buffer Gases to Increase the Efficiency of an Optically Pumped Far Infrared D sub 2 O Laser

摘要

The effects of buffer gas additives on the performance of an optically pumped D sub 2 O laser operating at 385 mu m have been investigated both experimentally and by numerical simulation. Three gases, sulphur hexafluoride, carbon tetrafluoride and n-hexane were found to produce an increase of up to 40% in the pumping efficiency, as well as significant lengthening of the far infrared pulse. Under optimum conditions 2.6 J in a 1 mu s long pulse have been obtained. The buffer gases are shown to eliminate the vibrational deexcitation bottleneck, which in pure D sub 2 O leads to an accumulation of population in the upper vibrational level, and hence a reduction in the efficiency of absorption of the pump beam. Comparison of the observed buffer gas effects with the predictions of a numerical simulation code based on a rate equation model gives information about the constants for vibrational and rotational relaxation rates due to D sub 2 O-D sub 2 O and D sub 2 O-buffer gas collisions. (ERA citation 12:008747)