Numerical modeling of stimulated Raman scattering in an astigmatic focus

A two-dimensional finite difference method is presented for the propagation of beams focused by an astigmatic lens. The method is used for the modeling of a Raman amplifier that uses astigmatic lenses. The effect of gain focusing on the amplification is studied with this method. The numerical results show a good correspondence with analytical models in the range where these models are applicable. It is shown that an astigmatic focus in a Raman amplifier lessens the problems of optical breakdown and ground-state depletion, and enhances the conversion efficiency, compared to an ordinary focus