Stimulated thermal scattering induced by two-photon absorption and experimental observeof genuine stimulated Brillouin scattering in the near-ultraviolet region

摘要

Some of the experimental measurements of the frequency shift and phase conjugation fidelity gained fromprevious studies of stimulated scattering (SS) of nanosecond (5-10 ns) near-ultraviolet (uv) (X=193–351 nm) laser pulses in liquids (hexane, heptane, and others) are found to disagree with the theory of SS,which takes into account only linear (single-photon) light absorption. To resolve the inconsistency, SS of XeC1excimer laser radiation (X=308 nm) with the duration of 8 ns in liquid hexane is investigated experimentally.A theoretical analysis of the results obtained revealed three nonlinear optical phenomena induced by theheating due to two-photon absorption: stimulated thermal scattering (two-photon STS-2), phase mismatch forstimulated Brillouin scattering (SBS), and phase self-modulation. The experimental SS spectrum contains twoadditional lines—a two-photon STS-2 line and a genuine SBS line in the near-uv region.