Design and Analysis of a THz Topological Frequency-Tunable Waveguide based on Valleytronics

In this work, we present a THz waveguide based on topological photonics, specifically utilizing the valley degree of freedom (DOF). Our device is designed to operate in two distinct frequency ranges: 0.7 to 0.9 THz and 1.4 to $\mathbf{1. 6}$ THz. The design is based on a 2D honeycomb lattice of silicon rods with a lattice constant of $100 \mu \mathrm{~m}$. This lattice structure allows for easier fabrication than more complex topological photonic structures. By breaking the inversion symmetry of the unit cell, we induce topological energy gaps and generate oneway edge states. We have demonstrated that these edge states are robust against kinks in the waveguide, achieving transmission efficiencies of over 90%. Additionally, we have studied how the distance between the two photonic crystal regions (VPC1 and VPC2) affects the transmission spectrum and the dispersion of the topological edge state. Increasing this distance flattens the edge state, indicating the potential to create slow-mode waveguides. The unique properties of our topological THz waveguide, such as backscattering-resistant propagation and the ability to tune frequency response, make it a promising candidate for next-generation high-capacity wireless communication systems. We believe this design approach could be valuable for developing THz demultiplexer components.