Terahertz Generation in Nonlinear Plasmonic Waveguides

In this paper, terahertz (THz) generation in nonlinear plasmonic waveguides is proposed and thoroughly investigated. The proposed plasmonic waveguide is composed of metal-insulator-metal nanostructure filled with lithium niobate. The THz generation is conducted by means of difference-frequency generation of surface plasmon-polariton (SPP) modes. The SPP modes are designed to be tightly confined inside the plasmonic waveguide, while the generated THz waves diffract rapidly to propagate outside the plasmonic waveguide. It then follows that the THz absorption is minimized. It is shown that viable THz generation can be achieved, despite the SPP losses, by properly choosing the SPP wavelengths and the waveguide dimension. Our numerical evaluations show viable THz generation over the entire frequency band from 1 to 10 THz. The proposed structure introduces a new modality of having the SPP modes totally confined inside a nanoscale waveguide, while most of the generated THz waves are (and thus interacting) with the surrounding medium of the waveguide. These properties promise potential applications in nanocommunication systems and body-centric nanonetworks.