A Low-Pump-Threshold High-Repetition-Rate Intracavity Optical Parametric Generator Based on Periodically Poled Lithium Niobate

A low-pump-threshold high-repetition-rate intracavity optical parametric generator (IOPG) by using a periodically poled lithium niobate (PPLN) is reported. The PPLN, which is 18.7mm long and has a grating period of 28.93μm at room temperature, is inserted in a diode-end-pumped Nd:YVO₄ laser with an acousto-optic Q switch. The parametric generation threshold is 1.3W (diode laser power) at a Q-switch repetition rate of 19kHz. At an incident diode pump power of 5W, an average signal output power of 280mW has been achieved. The signal pulse duration is approximately 85ns. By changing the crystal temperature from 120°C to 250°C, the signal wavelength can be tuned from 1.493μm to 1.538μm.