Collinear phase-matched terahertz-wave generation in GaP crystal using a dual-wavelength optical parametric oscillator

Tunable terahertz (THz)-wave generation in GaP crystal was theoretically and experimentally investigated using collinear difference frequency mixing. The wavelength range and length of GaP crystal for efficient difference frequency generation (DFG) were determined by calculating the phase-matching conditions. THz waves from 0.5 to 4.5 THz were generated by collinear phase-matched DFG using a dual-wavelength optical parametric oscillator with two $KTiOPO4$ crystals in the range of 930–1000 nm. A maximum THz output energy of 5.3 nJ/pulse (peak power of 0.66 W) at 1.9 THz was obtained when the pump energy was 1.2 mJ/pulse.