Terahertz wave generation in orientation-patterned GaAs using resonantly enhanced schemes

Zincblende semiconductors (GaAs, GaP) show great potential for quasi-phase-matched (QPM) THz generation because of their small (20 times less than in lithium niobate) absorption coefficient at terahertz frequencies, small mismatch between the optical group and THz phase velocities, high thermal conductivity, and decent electro-optical coefficient. Terahertz-wave generation was demonstrated recently in QPM GaAs, using optical rectification of femtosecond pulses. Here we report on a new efficient widely tunable (0.5-3.5 THz) source of THz radiation based on quasi-phase-matched GaAs crystal. The source is based on difference frequency generation inside the cavity of a synchronously pumped near-degenerate picosecond OPO and takes advantage of resonantly enhanced both the signal and the idler waves. THz average power as high as 1 mW was achieved in a compact setup.