Abstract
High-efficiency THz generation in quasi-phase matched (QPM) optically contacted GaAs (OC-GaAs) with near-Brewster angle pumping is studied numerically. The effective nonlinear coefficients d eff for different incident angles and polarization directions are investigated. Compared with the normal incidence case, reflection loss of the pump energy at OC-GaAs interfaces can be reduced by propagating the pump at a near-Brewster angle (66.92°). The effect of the air-gap spacings between adjacent OC-GaAs layers to the number of optimal QPM periods and the efficiency of THz generation are calculated. In our study, the number of optimal QPM periods of OC-GaAs is increased significantly from 12 in the normal incidence configuration to 25 in the near-Brewster angle pumped configuration, while the efficiency of THz generation is enhanced by more than 16 times. © 2007 Optical Society of America.