On realization of phase matching condition for terahertz generation via optical rectification under condition of interaction with resonant impurities

A physical mechanism for achieving phase matching in collinear geometry for generation of terahertz radiation via optical rectification is proposed. A laser pulse propagating in uniaxial crystal doped with two-level resonant impurities can lower its group velocity to terahertz phase velocity under a self-induced transparency regime. The generation is accompanied by an optical pulse modulation and red shifting of its spectrum.