Total internal reflection at conductive interfaces: Monolayer graphene for terahertz modulation

We have derived the Fresnel reflection coefficients incorporating both total internal reflection (TIR) and a conductive interface. Using this result we show that the reflectance in the TIR regime has a larger dependency on the optical conductivity of the conductive layer than the transmittance in the normal incidence regime. This suggests that a TIR prism with a controllable conductive layer such as back-gated graphene could be used to create an efficient terahertz modulator.