Unusual Otto excitation dynamics and enhanced coupling of light to TE plasmons in graphene

Abstract

Transverse-electric (TE) plasmons are a unique and unusual aspect of graphene's plasmonic response that are predicted to manifest when the sign of imaginary part of conductivity changes to negative near the spectral onset of interband transitions. Although thus far, a feasible platform for the direct experimental detection of TE plasmons at finite temperature is yet to be suggested. Here we analyze the dynamics of Otto-Kretschmann excitation of TE plasmons in graphene. We show that TE plasmons supported by graphene in an Otto configuration unusually exhibit a cutoff thickness between the coupling prism and the graphene layer that forbids their efficient coupling to an incident wave in the case of a singlelayer graphene at typical finite temperatures. In contrast, significantly increased coupling in the case of an N-layer graphene insulator stack, owing to an N-fold increase of the effective graphene conductivity as the insulator thickness approaches zero, is predicted to provide a TE plasmon resonance that is easily detectable at room temperature.