Investigation of high beam quality methane Raman laser

Although lasers generated by stimulated Raman scattering (SRS) were reported to have better beam quality in comparison with pump laser; once pump laser intensity exceeded the threshold of laser-induced-breakdown (LIB), Raman laser beam quality was deteriorated dramatically. In this study, the backward SRS (BSRS) pro-cess of methane pumped by 532 nm laser was applied to produce high beam quality seed Raman laser beam, and stimulated Raman amplification with configuration of collimated seed laser and pump laser counter-propagation (BSRA) was used to increase the pulse energy of Raman laser. With a seed Raman laser of 51.4 mJ, similar to 127.2 mJ Raman laser could be produced by BSRA process. Raman laser beam quality achieved M-x(2) = 2.52 and M-y(2) = 2.40, which were better than pump laser. The technique could be applied repeatedly; pulse energy and peak power of Raman laser could be further improved. This work provides of possible method to achieve high peak power (large pulse energy) Raman lasers with excellent beam quality.