The parametric theory of stimulated Raman scattering involving waves with spatial and temporal inhomogeneities is introduced. The method is simple, intuitive, and describes many coherent phenomena.
A theoretical analysis is made of the problem of parallel amplification of the Stokes signal in a nonmonochromatic spatially inhomogeneous pump field in stimulated Raman scattering. Expressions are obtained for the spatial and temporal characteristics of the process of amplification of the Stokes signal. It is shown that in the course of amplification the slowly varying amplitude of the Stokes signal field becomes similar to the slowly varying amplitude of the pump field. The relationships obtained apply also, subject to certain restrictions, to other types of scattering.
An experimental study of stimulated Raman scattering (SRS) has been performed using a subnanosecond pulse to investigate the statistical properties of Stokes light generation.1 There are macroscopic fluctuations of Stokes pulse energy as well as random generation of spatial mode patterns. When the scattering volume has a low Fresnel number, the spatial patterns of the SRS resemble cavity modes. When the Fresnel number is large, there are irregular structures appearing across the Stokes profile in a random fashion. A theoretical study of the spatial and temporal coherence properties of Raman generation using a Gaussian-profile pump pulse has also been carried out. Using a Gaussian-Laguerre mode expansion technique,2 it is found that the higher-order spatial coherence modes1 experience different gain than the lower-order spatial coherence modes, and consequently the temporal coherence associated with each individual spatial coherence mode is different.