Extraordinary high-harmonic generation from plasmons in nanostructured graphene

Abstract

High-harmonic generation (HHG) is an extreme nonlinear optical phenomenon that is traditionally realized by driving atomic gases with intense ultrashort optical pulses, and usually relies on bulky laser amplification schemes to reach the enormous requisite electric field intensities. The realization of efficient HHG in solid-state systems is anticipated to pave the way for compact ultraviolet and ultrafast light sources, and to provide fundamental insight into quantum many-body electron motion [1-3]. Here we demonstrate that the large light intensity required for HHG to occur can be reached by exploiting localized plasmons in doped graphene nanostructures. In particular, we demonstrate that the synergistic combination of strong plasmonic near-field enhancement and a large intrinsic nonlinearity originating from the anharmonic charge-carrier dispersion of graphene result in efficient broadband HHG within a single material [4]. Our conclusions are based on rigorous time-domain simulations using complimentary nonperturbative approaches based on atomistic one-electron density matrix and massless Dirac-fermion Bloch-equation pictures, where the latter treatment is supplemented by a classical electromagnetic description of the plasmonic near-field enhancement produced by the illuminated nanostructure.