Millimeter-long travelling wave photoconductors for THz generation by photomixing

In this communication we present the development of a travelling wave photoconductor for THz generation by photomixing. It is based on a silicon nitride optical waveguide coupled to a membrane-supported low-temperature-grown GaAs photoconductor embedded in a coplanar waveguide. The frequency response of a 1-mm-long structure, measured up to 100 GHz by using the beatnote produced by two 780-nm-DFB lasers, shows the expected travelling wave signature consisting in a 6-dB-decrease ending at ~50 GHz when the contribution of the backward travelling wave is fully cancelled, following by a constant level up to ~100 GHz.