A complex structure GaAs waveguide emitter with a periodic variation along the propagation direction for generation of terahertz radiation

摘要

A novel terahertz source that is capable of emitting terahertz radiation based on a phase-matched optical rectification process pumped by 1550-nm fiber lasers is proposed. The whole device equivalently consists of many THz-emitter units connected along the direction of optical pulses propagation by optical chirp compensation components such as photonic crystal fibers and optical semiconductor amplifiers. In each THz-emitter unit, there are two sections adjacent to each other along the direction of the pumping optical pulse propagation. One of the sections is a segment of asymmetric dielectric planar waveguide in which a core-layer of GaAs is contacted with a substrate containing an epilayer of Al_xGa_(1-x)As. The other section is a segment of corrugated waveguide with a GaAs second-order rectangular grating teeth layer above the same substrate containing an epilayer of Al_xGa_(1-x)As. 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 exploiting the waveguide mode dispersion. These terahertz waves then could be coupled into the air and the substrate transversely in the following grating section to form the terahertz radiation.