Investigation of optical absorption enhancement of plasmonic configuration by graphene on LiNbO3-SiO2 structure

Abstract

A novel plasmonic structure is demonstrated by combining graphene with a planar LiNbO3 thin layer, which is simple and easy to fabricate compared to the complex design of general graphene surface plasmons devices. Graphene from the chemical vapor deposition is investigated and characterized to be a continuous and uniform monolayer or fewlayer. LiNbO3 capped by graphene layer show an extraordinary absorption enhancement in an attenuated total reflection (ATR) measurement at a wide bandwidth of 500~4000 cm-1, which can be explained by resonance absorption resulting from the coupling of graphene surface plasmons with optical modes of LiNbO3-SiO2 Fabry-Perot cavity and LiNbO3 planar waveguide. The simulation results are generally consistent with the ATR experimental results. The absorption spectra versus temperature of this plasmonic configuration is also investigated, which show that increasing the testing temperature not only highlights the atomic vibrational peaks of graphene, but also enhances the absorption at several characteristic absorption frequencies due to the enhanced coupling between the surface plamons excitations and the optical modes.