Electrical control of second harmonic generation in a graphene-based plasmonic Fano structure.

Fajun Xiao,Weiren Zhu,Malin Premaratne,Ting Mei,Jianlin Zhao,Wuyun Shang

doi:10.1364/oe.23.003236

Abstract

We propose a strategy for active control of second harmonic generation (SHG) in a plasmonic Fano structure by electrically doping its underlying monolayer graphene. A detailed theoretical model for the proposed scheme is developed and numerical simulations are carried out to demonstrate the operation. Specifically, we show that a merely 30 meV change in graphene Fermi level can result in 45 times increase in SHG peak intensity, accompanied by a resonance wavelength shift spanning 220 nm. Further analysis uncovers that such tunability in SHG arises from the Fermi-level-modulated graphene permittivity, the real and imaginary parts of which dominate the resonance wavelength and the intensity of SHG, respectively.

Highlights

Localized surface plasmon resonances (LSPRs), the collective electron oscillations at surfaces of metallic nanostructures, have been a subject of intense studies owing to their ability to manipulate light at the nanoscale
We demonstrate that a broad tunable range (220 nm) in resonance wavelength and a 45 times increase in peak intensity can be achieved for the second harmonic generation (SHG) emission from our proposed Fano structure by slightly increasing the graphene Fermi level from 65 to 95 meV
By slightly changing graphene Fermi level, we show a tuning range as large as 220 nm for SHG resonance wavelength

Summary

Introduction

Localized surface plasmon resonances (LSPRs), the collective electron oscillations at surfaces of metallic nanostructures, have been a subject of intense studies owing to their ability to manipulate light at the nanoscale. The corresponding strong confinement of light leads to giant enhancement of electromagnetic field that makes incredibly weak physics processes observable This can be exemplified by the enhanced nonlinear optical processes, including second harmonic generation (SHG) [1,2], multiphoton luminescence [3,4], and four wave mixing [5,6]. To control the SHG in a plasmonic structure, it is necessary to effectively modulate the SHG source This can be realized by manipulating the radiative and nonradiative losses to alter the local field intensity at the fundamental frequency. We demonstrate that a broad tunable range (220 nm) in resonance wavelength and a 45 times increase in peak intensity can be achieved for the SHG emission from our proposed Fano structure by slightly increasing the graphene Fermi level from 65 to 95 meV. Compared with the traditional technique which relies on changing the geometry, the proposed graphene-based Fano structure provides a more flexible approach to engineer the SHG, which may potentially expand the application of SHG even further

Linear response of graphene-based Fano structure

SHG in graphene-based Fano structure

Conclusion