Stimulated thermal scattering induced by two-photon absorption and experimental observation of genuine stimulated brillouin scattering in the near-ultraviolet region

Part of the experimental measurements of the frequency shift and the phase-conjugation (PC) fidelity gained from previous studies of stimulated scattering (SS) of nanosecond ( 5 ~ 10 ns ) near-ultraviolet (UV) ( 193 ~ 351 nm λ = ) laser pulses in liquids (hexane, heptane, and others) are found to disagree with the theory of SS, which takes into account only the linear (single-photon) light absorption. To resolve the inconsistency, SS of XeCl excimer laser radiation ( 308 nm λ = ) with the duration of 8 ns in liquid hexane is investigated experimentally. A theoretical analysis of the results obtained revealed three new nonlinear optical phenomena induced by the heating due to two-photon absorption: stimulated thermal scattering (two-photon STS-2), phase mismatch for stimulated Brillouin scattering (SBS), and phase self-modulation. Experimental SS spectrum contains two new lines a previously unknown two-photon STS-2 line and a genuine SBS line newly discovered in the near-UV region.