Design of hybrid GaAs waveguide emitters for generation of terahertz radiation based on phase-matched optical rectification process pumped by 1550-nm fiber lasers

A GaAs waveguide emitter for terahertz radiation generation based on phase-matched optical rectification process pumped by 1550-nm fiber lasers is proposed as a potential terahertz source. The device consists of two waveguide structures which are adjacent to each other along the longitudinal direction of the waveguide. One of these is a segment of asymmetric dielectric planar waveguide in which a core-layer of GaAs is contacted with a substrate containing an epilayer of AlxGa1-xAs. The other is a segment of corrugated waveguide with GaAs second-order rectangular grating teeth layer above the same substrate containing an epilayer of AlxGa1-xAs. The terahertz waves could be generated in the non-grating section by a pulsed fiber laser based on an optical rectification process under the circumstance of phase matching by exploring the waveguide mode dispersion, which then could be coupled into the air and the substrate transversely by the following grating section to form the terahertz radiation. The coupling efficiency is estimated to be about 60% for an optimal designed terahertz wave emitter.