Efficient Raman laser system. using stimulated Brillouin scattering with different confocal parameters for CH4

Abstract

We report the efficient Raman laser system with the wavelength of 1.54 VLm from a passively Q-switched Nd:YAG laser with high-pressure methane gas. It has been known that the stimulated Brillouin scattering (SBS) prevents the Raman conversion. The efficiency of the Raman conversion, however, has been greatly enhanced with a specially designed lens to use a backward-stimulated Brillouin in our scheme. The special lens has a focal length of 12 cm, and a maximum conversion efficiency of 51% has been obtained with the first-Stokes energy of 32 mJ and the residual pump energy of 30 mJ at 1400 psi. Comparing two resonators with different focal lengths of the lenses, we have found that backward-SBS can be greatly enhanced by use of the shorter focal length of 12 cm, and the enhanced backward-SBS helps to increase the conversion efficiency. (c) 2007 Optical Society of America.