The light diffraction effect on stimulated Raman scattering.

The stimulated Raman scattering is simulated with different size of incident light using code LAP3D. The reflectivity of Raman scattering is very sensitive to the size of single speckle of the incident light. Small reflectivity is obtained when width of speckle is small, which is explained by the effect of light diffraction. For inhomogeneous plasma, the reflectivity is larger with a positive density gradient than that with a negative density gradient, which is consistent with the theory result. The incident light smoothed by the continuous phase plate contains many speckles and has an intensity distribution. The fractional power above intensity profile is very important, because the high intensity power can excite the stimulated Raman scattering and reduce the threshold of average intensity. [ABSTRACT FROM AUTHOR]