Tunable terahertz waves generated by mixing two copropagating infrared beams in GaP

By mixing two copropagating coherent beams near 1 mu m in a zinc blende GaP crystal, we have efficiently generated coherent terahertz (THz) waves. Such efficient conversion is made possible by use of a rest-strahlen band in the THz region to achieve phase matching in an isotropic crystal. A tuning range as wide as 71.1-2830 mu m (0.106-4.22 THz) was achieved, whereas the highest output peak power reached 15.6 W at 173 mu m. To obtain such a tuning range we continuously tuned the wavelength of one coherent infrared beam within a bandwidth of similar to 15.3 nm. (c) 2005 Optical Society of America.