Efficient MW-peak-power kHz-repetition-rate sub-nanosecond optical parametric generator tunable from near- to mid-infrared

•A widely tunable optical parametric generator (OPG) from near- to mid-infrared was achieved based on PPMgLN pumped by a sub-nanosecond pulsed laser.•The PPMgLN OPG produced kHz-repetition-rate pulses with peak power over 1 MW and high conversion efficiency up to 67.2%.•Theoretical models were built on the evolution of signal linewidth and beam profile during wavelength tuning of the OPG. A high-efficiency, high-peak-power, widely tunable optical parametric generator (OPG) based on a multi-period MgO-doped periodically poled lithium niobite (PPMgLN) crystal is presented. Pumped by a passively Q-switched microchip Nd:YAG laser with the pulse duration of 330 ps and repetition rate of 1 kHz, the OPG could be continuously tuned from 1399 nm to 4443 nm by changing the grating period and working temperature. The total output power of the signal and idler waves reached 591 mW, corresponding to the conversion efficiency of 67.2% and slope efficiency of 89.6%, the highest as far as we know. The maximum signal peak power was over 1.6 MW at 1758 nm. The evolution of line width and beam profile of the signal wave during wavelength tuning were also studied and the theoretical models were proposed.