Acousto-optic Q-switched intracavity Nd:YAG/RTP cascaded Raman laser characteristics

The intracavity cascaded Raman laser output characteristics based on potassium titanyle phosphate (RbTiOPO4, RTP) crystal were reported. A diode end-pumped acousto-optic Q-switched Nd:YAG laser at 1 064 nm was adopted as the fundamental light. A 4420 mm3 in size and along x-axis cut RTP crystal was used as the Raman gain medium. The RTP Raman laser systems with X(ZZ)X and X(YY)X configurations according to the Porto notations were designed for experimental study. The relatively low Raman gain of X(YY)X geometry configuration leads to the competition of different nonlinear frequency conversion processes in the cavity, and only the corresponding optical parametric oscillation output was measured. The cascaded Raman laser output with the Raman shifts of 271 cm-1 and 687 cm-1 was successfully achieved in the X(ZZ)X configuration. The high-order Stokes lines appeared successively with the increase of incident pump power. Total average output power of 480 mW and conversion efficiency of 4.8% were obtained under an incident pump power of 10 W and a pulse repetition frequency of 15 kHz. The laser wavelength includes different order Stokes ranging from 1 000 to 1 200 nm.