▎ 摘　　要

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 Omega, reemits radiation at frequencies m Omega with odd integer m. The graphene based frequency multiplier is tunable and can work in a broad frequency range, in particular, at terahertz frequencies. (C) 2007 Elsevier B.V. All rights reserved.