Abstract

The conversion efficiency of stimulated Raman scattering (SRS) is limited by the fact that the process builds up from spontaneous emission noise. The system used to overcome this limiting effect utilizes nonlinear frequency conversion in a glass fiber to produce a seed for the SRS, and it uses a capillary tube to confine the pump light in the gas. The experimental set-up includes a cell containing CH₄ at 560 1b/in², pumped at 532 nm by using a mode-locked, Q-switched, and frequency doubled Nd:YAG laser. With an average power of approximately 50 mW of the pump light split off to the fiber to produce the seed, a change in the intensity of the first Stokes line at ~630 nm was clearly visible. This corresponded to a conversion efficiency of 22% with only 40 mW of pump power at a Q-switch rate of 450 Hz. At higher powers a sizable anti-Stokes emission at 467 nm was also generated. The large conversion efficiency of this unoptimized system demonstrates the feasibility of SRS for obtaining multiple wavelengths with diode pumped laser systems.

© 1992 Optical Society of America