Semiconductor-Metal-Semiconductor Core-Multishell Nanowires as Negative-Index Metamaterial in Visible Domain

Abstract

Negative-index metamaterials (NIMs) exhibiting both negative refraction as well as phase reversal, particularly in the visible range, have drawn considerable attention in the past decade due to their potential applications in cloaking, sensing and sub-diffraction-limit imaging. NIM are often realized by arraying sub-wavelength nanostructures (meta-atoms) exhibiting spectrally overlapped magnetic and electric resonances. Most designs so far use scaling down of the resonant elements and employ materials with the right optical constants to obtain NIM in the visible range. However, large losses due to absorption in most metals and semiconductors as well as reduced coupling with light due to scaling pose a challenge to achieving low-loss NIM. Here, we employ plasmon hybridization in semiconductor-metal-semiconductor core-multishell (CMS) nanowires as a unique approach to design low loss, isotropic and polarization dependant NIM in the visible range. Based on numerical simulations, we demonstrate an effective refractive index of −1 and a figure of merit (FOM) of 17 at 650 nm for a representative Si-Ag-Si CMS nanowire NIM and a refractive index of −1, FOM of 25 at 590 nm for a GaP-Ag-GaP CMS nanowire NIM.