Multifunctional photonic crystal cross waveguide for terahertz waves

A multifunctional cross waveguide is designed based on the photonic crystal structure and the liquid crystal material. The different states of the cross waveguide controlled by the electric field make its various functions possible, including a switch with a high extinction ratio, a splitter that divides the terahertz wave into the desired proportions, and a through or 90° turn waveguide. The plane wave expansion method is used to calculate the bandgap in the photonic crystals, and coupling mode theory is adopted to analyze and eliminate the reflection loss. The finite element method is used to get the proper distribution of the external electric field. The properties of the cross waveguide are simulated by the finite difference time domain method, and the results show that the cross waveguide is a multifunctional device with high performance characteristics.