Abstract

The stimulated Raman scattering gain of a multiline pump laser spanning a sufficiently wide spectral range is significantly reduced from that of a narrowband laser. This is due to destructive interference between the narrowband Raman effect and the Raman-resonant four-wave mixing effect which couples the lines together. However, this interference can be constrained to be always constructive by angle tuning of the pump and Stokes seed input beams to satisfy a phase matching condition for the four-wave mixing. The narrowband Raman gain will then be obtained. Calculations for a two-line XeF laser in a Raman conversion cell show that submilliradian beam angles can shorten the required cell length by factors of ~2, while loosening the pump intensity variation tolerance by an order of magnitude. Calculations for lasers with wider spectra indicate the potential for much larger gain increases and cell length reductions.

© 1988 Optical Society of America