RAMAN SHIFTING IN THE ABSENCE OF MULTIPLE STOKES ORDERS WITH A ND-YAGLASER IN HYDROGEN - EVIDENCE OF COUPLING BETWEEN THE FORWARD AND BACKWARD STOKES PROCESSES

By Raman shifting the output of a 1.319-mu m Nd:YAG laser in hydrogen, up to 24.5 mJ of Stokes light at 2.918 mu m has been generated. Due t o the low energy of the 2.918-mu m Stokes photons, the first Stokes is the only Stokes line for this system. The effect of pressure on the c onversion is notably simpler in this regime, but the gain saturates un usually slowly, An unexpected pump linemidth sensitivity in the forwar d Stokes conversion is observed. Coupling of tile forward and backward Stokes processes is suggested as an explanation for these effects and is supported by a simple model.