The Roles of Substrate vs Nonlocal Optical Nonlinearities in the Excitation of Surface Plasmons in Graphene

TL;DR

This paper compares substrate and graphene nonlinearities in generating surface plasmons via difference frequency mixing, revealing that graphene's intrinsic nonlocal response dominates over substrate effects by twelve orders of magnitude.

Contribution

It provides detailed calculations showing the dominance of graphene's intrinsic nonlocal nonlinearities over substrate contributions in surface plasmon excitation.

Findings

Graphene's nonlinear response is twelve orders of magnitude stronger than the substrate's.

Nonlocal contributions enable significant second-order nonlinearity in centrosymmetric graphene.

Intrinsic graphene nonlinearity is the primary driver for surface plasmon excitation in DFM.

Abstract

It has recently been demonstrated that difference frequency mixing (DFM) can generate surface plasmons in graphene [1]. Here, we present detailed calculations comparing the contributions to this effect from substrate and from graphene nonlinearities. Our calculations show that the substrate (quartz) nonlinearity gives rise to a surface plasmon intensity that is around twelve orders of magnitude smaller than that arising from the intrinsic graphene response. This surprisingly efficient intrinsic process, given the centrosymmetric structure of graphene, arises almost entirely due to non-local contributions to the second order optical nonlinearity of graphene.