Ring cavity solid-state Raman lasers generating in visible and eye-safe spectral regions

The present report gives results on development of two Raman lasers with ring cavities. Both lasers use triangular architectures of a cavity with three plane mirrors and KGW crystals as active medium. Each cavity mirror has special spectral response providing optimal optical feedback at the 1st Stokes wavelength and low feedback at high-order Stokes wavelengths. Preliminary investigations demonstrated realization of bidirectional Stokes generation with single frequency laser pump. In contrast, pump radiation with a spectral bandwidth typical for solid-state lasers could provide stable generation in only one direction. The necessary condition of the unidirectional generation was found to be elimination of residual optical feedback arising at the crystal ends. This case, asymmetry of the Raman gain in opposite directions was sufficient to effectively suppress backward Stokes generation.