Large aperture PPMgLN based high-power optical parametric oscillator at 3.8 µm pumped by a nanosecond linearly polarized fiber MOPA.

We report a large aperture PPMgLN based OPO generating 21W of average output power at a slope efficiency of 45%. The OPO is pumped with the output from a polarization maintaining Ytterbium doped fiber MOPA operating at 1060nm producing 20ns pulses at a repetition rate of 100kHz and an average output power of 58W (after the isolators). A maximum of 5.5W of optical power was recorded at the idler wavelength of 3.82µm without thermal roll-off. The pulse rise/fall time plays a significant role in the OPO conversion efficiency and that further enhancements in the efficiency should be possible using pulses with faster rise and fall times.