Backward Raman gain measurements for KrF laser radiation scattered by CH4

Backward Raman small-signal gain measurements for a KrF laser scattered by methane gas, including linewidth and pressure dependences, are presented. A 268-nm probe beam is produced from a 249-nm pump beam by superfluorescent emission in a methane cell, and is amplified by a counterpropagating KrF beam at 249 nm in a second methane cell. The results are consistent with theoretical predictions for the backward Raman amplifier.