Tunable terahertz narrowband filter based on heterostructure waveguides filled with liquid-crystals

We propose a tunable waveguide-type terahertz (THz) narrowband filter based on heterostructure waveguide filled with liquid-crystals (LCs). This filter consists of two periodic corrugated waveguide structures with different duty cycles, which produces a narrow linewidth transmission peak within the original stop band. By adjusting the effective refractive index of LC through external fields, the center frequency of the transmission peak can be tuned. The simulated electric field proves that the narrow linewidth transmission peak is mainly attributed to the local resonance occurred at the interface. Furthermore, an increase in the number of periods can greatly reduce bandwidth and improve the Q-factor of the filter. The proposed electrically tunable THz narrowband filter based on the heterostructure waveguide provide an effective method for the design and development of THz narrowband filter.