Effects of off-resonant Raman interactions on multimode Stokes conversion efficiency and output wave front

Abstract

Interactions involving frequency differences that are near but not equal to the Raman shift are considered in a model of stimulated Raman conversion of a laser beam with many longitudinal modes. A formalism based on expansions in mode space is developed and used to predict the effects on output wave front and conversion efficiency. Closed-form solutions are obtained for the case of detuned inputs with large mode spacing and for low conversion cases. Numerical integration results are shown for low to high conversion examples in which only first-order off-resonant terms are important.