Effects of Stimulated Raman Scattering on Light Beam Properties During High-Power Laser Beam Long-Path Propagation.

摘要

Beginning from the third-order nonlinear polarization from the stimulation and induction of matter based on the semiclassical theory of stimulated Raman scattering (SRS), a theoretical model of coupling between the phase of a pump (transmission) laser beam and the phase of the Stokes beam intensity is established for the case of stimulated Raman scattering during long-path propagation of a high-power laser. The model clearly explains how the SRS effect influences the beam properties of the pump laser, including the physical regime and effective factors of time-domain properties and space-domain properties (light beam quality). The theoretical analysis is in fairly satisfactory agreement with the experimental results. In the experiments, measurements of time-domain properties were taken of the pump laser beam and the Stokes beam after transmission in a situation with various conversion efficiencies Ns. As shown by the results, under conditions of low-conversion efficiencies, basically the time-domain properties of the pump laser beam are not affected by the SRS effect. But when the conversion efficiency Ns is greater than 5 percent, the pulse duration of the pump laser beam is gradually reduced as Ns is increased. Stimulated raman scattering, Pump laser beam, Stokes beam, Far-field divergency angle.