Continuous-wave difference frequency generation in the mid-infrared with orientation-patterned gallium phosphide (OP-GaP) crystals

Orientation-patterned gallium phosphide (OP-GaP) crystals are used here for the first time for the generation of continuous-wave coherent mid-infrared radiation around 5.85 mu m by difference frequency generation (DFG) of a Nd:YAG laser at 1064 nm and a diode-laser at 1301 nm. We provide the first characterization of the linear, thermo-optic and nonlinear properties of OP-GaP in a DFG configuration, and we derive an effective nonlinear coefficient d(eff) = 17 pm/V (3) for first-order quasi-phase-matched OP-GaP. This novel nonlinear material can be used to referenced the mid-IR light to a frequency standard by locking the pump and signal laser to a near-IR optical frequency comb.