Secondary Raman and Brillouin mode suppression in two- and three-mirror-cavity diamond Raman lasers
Muye Li, Xuezong Yang, Yuxiang Sun, Huawei Jiang, Richard P. Mildren, Ondřej Kitzler, David J. Spence, Yan Feng
Abstract
We report an investigation into secondary mode suppression in single longitudinal mode (SLM) 1240 nm diamond Raman lasers. For a three-mirror V-shape standing-wave cavity incorporating an intra-cavity LBO crystal to suppress secondary modes, we achieved stable SLM output with a maximum output power of 11.7 W and a slope efficiency 34.9%. We quantify the level of χ (2) coupling necessary to suppress secondary modes including those generated by stimulated Brillouin scattering (SBS). It is found that SBS-generated modes often coincide with higher-order spatial modes in the beam profile and can be suppressed using an intracavity aperture. Using numerical calculations, it is shown that the probability for such higher-order spatial modes is higher for an apertureless V-cavity than in two-mirror cavities due its contrasting longitudinal mode-structure.