The investigation of stimulated Raman scattering in gases under di-harmonic pumping

An investigation was made of the features of the competing effects in gaseous stimulated Raman scattering (SRS) under single and di-harmonic pumping. Firstly, the one aim of this work was to observe the variations of forward and backward SRS generation in CH4 gas under di-harmonic pumping composed of 1064 nm and 532 nm lasers. At low pressure di-harmonic pumping suppressed backward SRS of 1064 nm beam, and enhanced its output energy of forward SRS. Secondly, di-harmonic pumping of 1064 nm and 1.54μm radiations obviously suppressed stimulated rotational Raman scattering, and enhanced its stimulated Raman vibrational scattering at high pressure of H2 gas. A 13.6 mJ 4.30μm mid-infrared Raman laser under di-harmonic pumping was obtained with the H2 gas pressure of 3.4 MPa. The corresponding photon conversion efficiency was 41.9%, and peak power reached 9.4 MW.