On the angular spectra of anti-Stokes stimulated Raman scattering under self-focusing

It is shown in this work, by the example of the first anti-Stokes component in toluene, that a high efficiency of conversion of laser radiation into the Stokes component in the focal regions of self-focusing (SF) plays a decisive role in the formation of the angular structure of radiation. The inclusion of a high efficiency of pumping conversion into the Stokes component in SF allows the basic regularities of the formation of the angular structure of an anti-Stokes radiation to be determined. The length of the domain of existence of the nonlinear polarization at the anti-Stokes frequency is expressed in this case in terms of optical parameters of a light-scattering medium, where this quantity is introduced by way of matching the calculated and the observed angles of preferable radiation. Moreover, the longitudinal distribution function of the nonlinear polarization turns out to be distinct from the Gaussian one proposed previously. The results of the calculations carried out are compared with experimental data obtained for toluene in a cell 25 cm long in which SRS was excited by single pulses 20 ns long with an energy of 0.6 J from a ruby laser with passive Q-switching.