Symmetry breaking-induced resonances with more efficient terahertz reflections

Abstract

We report our experimental observation and theoretical and numerical validation of a new type of THz resonance and bandgap induced by symmetry breaking in a periodically corrugated parallel plate waveguide. Unlike the familiar Bragg resonances, the observed unusual resonance is found to result from the strong interaction between THz wave modes with different transverse standing-wave profiles that occurs far away from the edges of the Brillouin zone. Unexpectedly, such resonance depends strongly on the mirror symmetry of the waveguide and can produce exceptionally strong power attenuation and a wider and steeper frequency bandgap for THz waves. THz bandgap properties of waveguides with different symmetries can be identified unambiguously by the simulated dispersion diagrams, electric fields, and mode analysis. Symmetry breaking-induced THz resonances will not only benefit the understanding of wave propagation in complex waveguides but also open a new pathway to design more complex band structures in applications such as high-speed communications.