Abstract

Multiple high-Stokes and anti-Stokes orders are frequently observed in stimulated Raman scattering (SRS). In the vast majority of cases, the higher orders are the result of parametric 4-wave processes occurring under phase-matched conditions. This phase matching requires that the various orders are generated at widely differing angles and the resulting multifrequency beam is not focusable to a single spot. The much more interesting case is where higher orders are generated with a phase mismatch but are collinear. Such a beam may have application to laser fusion.^1,2 The rotational transitions in gases have been extensively used in Raman amplification, and, recently, multiple components of comparable amplitude spanning a broad bandwidth have been generated using both H₂ and N₂ gas.^3,4 Previously, it has been thought that it would not be possible to switch on bandwidth on a timescale much shorter than the dephasing time of the medium, T₂, and that this delay would severely limit the usefulness of the generated spectrum.^1,2 Experiment has tended to support this conclusion.⁴

© 1994 IEEE