Optimized 4-µm OPO with intracavity OPA based on a dual-grating PPLN crystal

Here, we use a dual-grating PPLN crystal containing a uniform-grating OPO section followed by a fan-out grating OPA section. In this way, phase-matching can be independently set for the OPO process by adjusting the temperature and the OPA process by translating the crystal. Such an approach was previously reported in the case of cascaded cw OPOs (the signal acts as the pump of a second OPO) but was never investigated for an OPO-OPA device. We investigate such an OPO-OPA scheme in the nanosecond regime at a higher average power (up to 10 W of pump power) and at longer idler wavelength (~ 4 μm) than reported in previous works.