Efficient parametric terahertz generation in quasi-phase-matched GaP through cavity enhanced difference-frequency generation

We report an efficient parametric terahertz (THz) source by using bonded quasi-phase-matched (QPM) GaP crystals pumped by the C-band pulsed fiber lasers in a master oscillator power amplifier configuration, based on difference frequency generation (DFG). We observed that the QPM-GaP crystals can effectively increase the THz generation power and efficiency by increasing the number of periods. Moreover, we observed external cavity enhanced THz DFG by placing the QPM-GaP crystal in an external ring cavity. The THz cavity enhancement factor of approximately 250 has been achieved in comparison with a single-pass THz DFG. The maximum THz average power can reach 339 μW, corresponding to a power conversion efficiency of 2.43×10−4 and a quantum efficiency of 3.16%.