Active control of terahertz wave assisted by dielectric loaded plasmonic waveguide

We propose and numerically investigate a directional coupler which consists of two dielectric loaded InSb based terahertz (THz) plasmonic waveguides. Owing to the permittivitly tunable property of InSb, the coupling strength between the two dielectric loaded plasmonic waveguides is affected by temperature, so the maximum power coupled from the input waveguide to the cross-waveguide and the correspondingly coupling length could be effectively tailored by altering temperature. Under different temperatures, this directional coupler could act as a thermally controlled terahertz wave switch or a 3-dB terahertz splitter around the frequency of 1.17 THz. This ultracompact and thermally controlled plasmonic directional coupler may find potential important applications in the highly integrated photonic circuits for terahertz system and technologies.