Electromagnetic response of electrons in graphene: Non-linear effects

Electrons and holes in graphene have a massless, Dirac energy spectrum. This leads to strongly non-linear electromagnetic response: The graphene layer, irradiated by electromagnetic waves with the frequency ΩΩ, reemits radiation at frequencies mΩmΩ with odd integer mm. The graphene based frequency multiplier is tunable and can work in a broad frequency range, in particular, at terahertz frequencies.