Total cross-polarization conversion and polarization-sensitive amplification of terahertz radiation in graphene with direct electric current

In this letter, we predict the effect of the total cross-polarization conversion of transverse-magnetic electromagnetic wave incident upon drift-current biased graphene into a reflected wave with transverse-electric polarization, which can be possible in the total reflection regime. It is shown that the degree of polarization conversion depends on the angle between the stationary drift-current direction and the plane of the wave incidence. Total polarization conversion is promoted by excitation of the hybrid electromagnetic mode (having a mixed polarization) in graphene. Remarkably, this effect is unrelated to the spatial dispersion of graphene conductivity. This is a unique feature of graphene, which does not exist in conventional two-dimensional electron systems with massive charge carriers. The hybrid electromagnetic mode in graphene can enter the self-excitation regime in the terahertz (THz) frequency range due to the negative real part of graphene conductivity induced by drift current. The studied effects can be useful for creating compact electrically and/or optically tunable polarization convertors and polarization-sensitive amplifiers of THz radiation.