Continuous-Wave Widely Tunable MgO:PPLN Optical Parametric Oscillator With Compact Linear Cavity

An efficient continuous-wave, widely tunable, intra-cavity optical parametric oscillator (OPO) based on periodically poled MgO:LiNbO3 (MgO:PPLN) with a compact three-mirror linear cavity was demonstrated. The mode radii of fundamental and OPO cavities with plane and concave mirrors were calculated and theoretically compared. The result shows that the fundamental laser beam could be compressed, and its power density on the MgO:PPLN crystal could be improved by optimizing concave radii of cavity mirrors. Meanwhile, better mode matching between fundamental cavity and OPO cavity could be realized. A widely tunable signal spectrum from 1.43 to $1.79~\mu \text{m}$ and an idler spectrum from 2.62 to $4.16~\mu \text{m}$ were achieved as the OPO system derived by a diode laser end-pumped Nd:YVO4 crystal laser at 1064 nm. The maximum total output power up to 6.35 W (signal output power of about 4.24 W at $1.60~\mu \text{m}$ and idler output power of about 2.11 W at $3.17~\mu \text{m}$ ) and conversion efficiency of 31.6% were obtained at an incident pump power of 20.1 W.