Abstract-Plasmon Enhanced Terahertz Emission from Single Layer Graphene

Young-Mi Bahk , Gopakumar Ramakrishnan ,Jongho Choi , Hyelynn Song , Geunchang Choi ,Yong Hyup Kim , Kwang Jun Ahn , Dai-Sik Kim , and Paul C. M. Planken

ACS Nano, Just Accepted Manuscript

DOI: 10.1021/nn5025237

Publication Date (Web): August 19, 2014

Copyright © 2014 American Chemical Society

http://pubs.acs.org/doi/abs/10.1021/nn5025237

We show that surface plasmons, excited with femtosecond laser pulses on continuous or discontinuous gold substrates, strongly enhance the generation and emission of ultrashort, broadband terahertz pulses from single layer graphene. Without surface plasmon excitation, for graphene on glass, ‘non-resonant laser-pulse-induced photon drag currents’ appear to be responsible for the relatively weak emission of both s- and p-polarized terahertz pulses. For graphene on a discontinuous layer of gold, only the emission of the p-polarized terahertz electric field is enhanced, whereas the s-polarized component remains largely unaffected, suggesting the presence of an additional terahertz generation mechanism. We argue that in the latter case, ‘surface-plasmon-enhanced optical rectification’, made possible by the lack of inversion symmetry at the graphene on gold surface, is responsible for the strongly enhanced emission. The enhancement occurs because the electric field of surface plasmons is localized and enhanced where the graphene is located: at the surface of the metal. We believe that our results point the way to small, thin and more efficient terahertz photonic devices.