Stimulated Raman emission at 8·84 μm

Abstract

Focusing the output of a Q-switched ND3+: glass laser (frequency 9441 cm-1) into a high-pressure hydrogen cell (hydrogen molecular vibration frequency 4155 cm-1) produces second Stokes stimulated Raman emission at 9441 - (2 × 4155) = 1131 cm-1 or 884 μm. The dependence of this emission on hydrogen pressure has been investigated, the maximum power of 180 w being reached when the gas pressure was 250 lb in-2, the laser power 30 MW, and the first Stokes power (at 189 μm) 2 MW. At laser powers above 30 MW evidence for plasma formation is presented, and this is put forward as the reason why the output at 884 μm cannot be increased beyond 180 w.