Cherenkov-phase-matched nonlinear optical detection and generation of terahertz radiation via GaAs with metal-coating.

Terahertz (THz) wave detection and emission via Cherenkov-phase-matched nonlinear optical effects at 1.55-µm optical wavelength were demonstrated using a GaAs with metal-coating (M-G-M) and bare GaAs as a reference sample in conjunction with a metallic tapered parallel-plate waveguide (TPPWG). The metal-coated GaAs is superior to the bare wafer both as a THz electro-optic detector and as an emitter. Significant improvements in the detection and emission efficiency were obtained by utilizing a metal-coating due to better confinement and lower loss of the THz waves propagating in the M-G-M compared with bare GaAs.