The study of threshold and intensity of SRS in the rubidium vapour at the various spectral ranges of pump radiation

We study experimentally the frequency dependence of the excitation threshold and the intensity of induced Raman scattering in rubidium vapor near the resonant transitions Rb 5$^{2}$S$_{1/2}—5^{2}Р_{1/2,3/2}$, while varying the pumping line-width between 0.2 and 20 cm$^{-1}$. In the immediate vicinity of resonance, we observe a sharp increase of the threshold and a decrease of intensity of the induced Raman scattering. In contrast with the backward scattering, under excitation of the forward induced Raman scattering the maximum of the scattered radiation is reached at large deviations from resonance of the order of several tens of cm$^{-1}$.