Terahertz Resonances of Transverse Standing Waves in a Corrugated Plate Waveguide

Terahertz (THz) propagation in periodic structures has attracted great attention because of its captivating electrical and optical properties. However, the created THz band gaps are usually considered to be caused by Bragg resonances. Here, we theoretically and numerically investigate THz resonances and their related band gap properties in a periodically corrugated plate waveguide with arbitrary wall profiles. It has been found that the corrugated structure can cause not only the interaction between the same transverse modes, called the Bragg resonance, but also the strong interference between different transverse standing wave modes, which occurs in a higher frequency range with quite different features. Unlike the well-known Bragg resonance, the excited resonances between different transverse modes can produce the stronger energy attenuation and wider frequency band gap. The dispersion diagram is depicted to clearly describe the relationship between these resonances and waveguide geometries. Using this method, we can properly estimate the band gap structure of THz waveguides, which has been confirmed by the simulated results. In addition, these two resonances can be easily manipulated by changing the symmetry of waveguide structures. These findings on THz propagation in periodic waveguides could be applicable in high performance devices, such as filters, modulators and switches.