Tunable terahertz Dirac-semimetal hybrid plasmonic waveguides

Abstract

Based on the Dirac semimetals (DSM) modified hybrid plasmonic waveguides, the tunable propagation properties have been systematical investigated by using the finite element method in the THz region, including the influences of structural parameters, the shape of dielectric fiber and Fermi levels of DSM layers. The results show that as the operation frequency increases, the real part of propagation constant increases, and the loss shows a peak. The shape of dielectric fiber (the elliptical structural parameter δ) affects the propagation property obviously, as the structural parameter decreases, the confinement and figure of merit increase, the loss reduces. With the increase of Fermi level of DSM layer, the imaginary part of propagation constant decreases, the modulation depth of loss is more than 95% if the Fermi level changes in the range of 0.01-0.15 eV. In addition, as the permittivity of dielectric material filling in the slit increases, the mode confinement and loss increases, FOM decreases. The results are very helpful to understand the tunable mechanisms of hybrid waveguides and design novel plasmonic devices in the future, e.g. modulators, filters, lasers and resonators.