Investigation of the forward and backward scattering of spatially noncoherent pump radiation

A new method developed by the authors for the analysis of stimulated scattering of spatially noncoherent radiation is used in a comparative study of the concurrent and opposed interactions of a Stokes field with pump radiation. If there is no correlation between the Stokes and pump waves, the interaction is independent of the relative direction of propagation of the waves. However, if the Stokes and pump waves are correlated, the interaction efficiency depends strongly on the relative directions of the waves. Exact expressions are obtained for the structure of the wave fields and gain increments in the backscattering case and approximate expressions are obtained for the forward scattering. The physical reason for the asymmetry in the amplification is the reproduction by the Stokes signal spectrum of the pump spectrum in the forward scattering case and inversion of this spectrum in the backscattering case. The same reason accounts for a deterioration of the quality of wavefront reversal in the backscattering case compared with the forward scattering.