Picosecond laser with discrete frequency tuning in the visible range utilizing stimulated Raman scattering with nonlinear mixing

A YAG:Nd³⁺ laser emitting radiation at eight frequencies in the visible range has been developed. This continuously pumped passively mode-locked laser contained an intracavity LiIO₃ crystal which served both as a Raman-active medium and as an element for nonlinear frequency mixing. Processes of stimulated Raman scattering with nonlinear mixing in an LiIO crystal were analyzed. It was established that the phonon mode having the E₂ symmetry (ν = 824 cm^–1) and the tilted polariton vibration having the A + E₁ symmetry (ν ~ 650 cm^–1) are actively involved in the emission process. Continuous frequency tuning could be achieved because of the angular dispersion of the tilted polaritons.