Design of reconfigurable metallic slits for terahertz beam modulation.

We analyze the interaction of electromagnetic waves with double-layered subwavelength metallic slits on a dielectric substrate. This structure allows efficient transmission of an incident TM-polarized electromagnetic wave into the dielectric substrate, due to the presence of surface modes which couple the incident wave to the TEM waveguide modes supported by the subwavelength metallic slits. Our study shows that electromagnetic transmission through double-layered subwavelength metallic slits is strongly geometry dependent. Based on this observation, a terahertz modulation scheme is presented which, compared to existing terahertz modulator solutions, has the promise of significant enhancement in modulation index over a broad range of terahertz frequencies.