Investigation of self-focusing in the case of stimulated Raman scattering of light

An investigation was made of the influence of different excitation conditions on the self-focusing of stimulated Raman-scattered light. It was found that the dimensions of self-focusing filaments and their number depended on the energy of the exciting radiation and the thickness of the scattering layer. In the situation in which self-focusing points were observed at both ends of a Dewar flask, the anti-Stokes scattering included (in addition to rings of class 1) scattering along the axis. Estimates were obtained of the self-focusing threshold power related to the Kerr effect and to the increase in the polarizability of molecules due to excitation. It was found that the first of these mechanisms could not give rise to self-focusing of the Raman-scattered light, whereas the threshold of the second mechanism was close to the excitation energy at which such self-focusing was observed.