Modulation and enhancement of optical absorption of graphene-loaded plasmonic hybrid nanostructures in visible and near-infrared regions

Abstract

Modulation and enhancement of the optical absorption of graphene-loaded plasmonic hybrid nanostructures is one of the important challenges for applications of graphene in advanced nanoelectronic and nanophotonic devices. In this paper, we study systematically the modulation and enhancement of optical absorption of the metal (Au)/graphene/dielectric/metal (Au) (MGDM) structure in visible and near-infrared regions. We find that the absorption intensity of the MGDM structure is significantly enhanced and is about three times higher than the absorption intensity of the traditional metal (Au)/graphene/dielectric (MGD) structure. Next, the dependence of the absorption spectra of the MGDM structure on the parameters of it, the refractive index of the external environment, the refractive index of the dielectric layer, and the graphene Fermi energy is studied. Results show there are optimal parameters of the MGDM structure for maximum absorbance of it. The absorption spectra of the MGDM structure are very sensitive to the refractive index of the external environment and the refractive index of the dielectric layer. Active modulation of the absorption spectra of the MGDM structure is realized by changing the graphene Fermi energy, and the modulation depth can be as high as 27.5%. Finally, the multi-peaks and the broad bandwidth phenomenon of the absorption spectra can be realized by forming a multi-MGDM structure. This study provides a promising platform for the application of graphene in photodetectors, tunable optical modulators, photovoltaic cells, and other plasmonic modulation devices.