A new mechanism to design transparent electrodes: THz realizations

We proposed a simple scheme to make a continuous metallic film on a semi-infinite substrate optically transparent, thus obtaining a completely transparent electrode in a desired frequency range. By placing a sub-wavelength composite layer consisting of dielectric and metallic stripes on top of the metallic one, we found that the back-scattering from the metallic film can be almost perfectly canceled by the composite layer under certain conditions, leading to transparency of the whole structure. Since our mechanism does not require any openings on the opaque metallic plate, the proposed structure retains the full electric and mechanical properties of a natural metal. The present mechanism is insensitive to structural disorders and broad variation of incidence angles. Meanwhile, we performed proof-of-concept experiments in the terahertz domain to verify our theoretical predictions, using carefully designed metamaterials to mimic plasmonic metals in optical regime. Experiments are in excellent agreements with full-wave simulations.