Terahertz shifted optical sideband generation in graphene

Exploration of optical nonlinear response of graphene predominantly relies on ultrashort time domain measurements. Here we propose an alternate technique that uses frequency shifted continuous wavefront optical fields, thereby probing graphene's steady state nonlinear response. We predict frequency sideband generation in the reflected field that originates from coherent electron dynamics of the photoexcited carriers. The corresponding threshold in input intensity for optimal sideband generation provides a direct measure of the third-order optical nonlinearity in graphene. Our formulation yields analytic forms for the generated sideband intensity, is applicable to generic two-band systems and suggests a range of applications that include switching of frequency sidebands using nonlinear phase shifts and generation of frequency combs.