High-efficiency terahertz wave amplification by coupled cascaded optical parametric processes

•THz wave is amplified by two cascaded parametric processes at coupling points.•More than 7THz photons are produced from a pump photon by 12orders CCOPP.•Quantum efficiency could exceed 7000% at 100 K with more cascading orders. A high-efficiency terahertz (THz) wave amplification approach by coupled cascaded optical parametric processes (CCOPP) with orientationally patterned gallium phosphide (OP-GaP) is introduced. The CCOPP comprises two cascaded optical parametric processes (COPP) which are intensely coupled by THz waves and cascaded optical waves via setting a precise periodic vector of OP-GaP. A simulation model that solves for the interactions of THz and cascaded optical waves is employed. The influences of cascading orders, phase mismatches, pump intensities, red-shifted and blue-shifted processes, nonlinear coefficients and absorption coefficients, the initial THz intensities are considered in the calculations. Simulation results predict that more than 7 THz photons are produced from a pump photon by 12 orders CCOPP.