Coherent monolithic THz generation based on quasi-phase-matched GaP bonded structures pumped by pulsed fiber lasers at ~ 1.5 μm

We report coherent monolithic THz generation in GaP QPM bonded structures based on difference-frequency generation (DFG) using two pulsed fiber lasers in the C-band. We observed that the QPM-GaP crystals effectively increase the THz generation power and efficiency with increasing periods of QPM structures. The azimuthal dependence of the THz generation for the GaP QPM bonded structure has been measured when the polarization directions of the two pump beams are orthogonal and parallel, respectively. Moreover, we observed the external cavity enhanced THz DFG when we put the QPM-GaP crystal in an external ring cavity, for the first time. The THz cavity enhancement factor of ~250 has been achieved compared with the 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 quantum efficiency of 3.16%.

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