Light-induced frequency shift of stimulated Raman scattering in Bessel light beams

Abstract

The medium susceptibility related to stimulated Raman scattering (SRS) is known to be a complex value whose imaginary part determines the SRS gain coefficient whereas the real part constitutes a small fraction of the refractive index at the frequencies of the scattered emission that is proportional to the intensity of the exciting beam. Strong transverse nonuniformity of this beam causes focusing of high-frequency components of the scattered light and defocusing of low-frequency ones that inevitably affect their amplification efficiency. The effect for Gaussian pumping is responsible for a slight shift of the SRS gain spectrum towards higher frequencies. The present work analyzes theoretically SRS excited by a Bessel light beam and demonstrates that the axial component of the scattered emission experiences a frequency shift that is much greater than that for the case of Gaussian beam pumping.