Development of the 2.8 microm emission doubly shifted Raman laser using stimulated Brillouin scattering in a cascaded cavity.

A doubly shifted Raman laser using CH(4) gas has been developed for 2.8 microm generation, pumped by a Nd:YAG laser with 65.5 mJ at 17 ns. A dichroically coated meniscus-type lens is modified to utilize the backward stimulated Brillouin scattering and backward Stokes beams from a previous laser design [Appl. Opt.46, 5516-5521 (2007)APOPAI0003-693510.1364/AO.46.005516]. A maximum output energy of 4.76 mJ at 2.80 microm wavelength has been achieved in the cascaded resonator. A maximum conversion efficiency of 8.9% has been achieved at a CH(4) gas pressure of 600 psi. The obtained spatial beam profile is quite smooth, and its output pulse width is 10 ns.