Diamond Raman laser for hydroxyl radical planar laser-induced fluorescence

This Letter describes, to the best of our knowledge, the first application of an Nd:YAG-pumped diamond Raman laser (DRL) for OH planar laser-induced fluorescence (PLIF). DRL was used to convert 532 nm pump radiation into 573 nm output, corresponding to the 1^st Stokes Raman shift, via the stimulated Raman scattering process in a diamond crystal, with an achieved conversion efficiency of 52%. The 573 nm output was then doubled to generate the UV radiation targeting the Q₁(14) OH transition near 286.5 nm. The overall conversion efficiency from 532 nm pump to 286.5 nm UV output was recorded at 5%. This demonstration was performed in methane/air combustion produced by a Hencken burner. Single-shot OH PLIF images were acquired in premixed "flat" flame and diffusion flame configurations with 160 µJ UV pulse energy and 5 cm sheet height. Overall, the DRL proved to be a promising and easy-to-implement alternative for combustion diagnostics and OH spectroscopy.