Ultra-narrow Line Width Polarization-Insensitive Filter Using a Symmetry-Breaking Selective Plasmonic Metasurface

Abstract

Plasmonic metasurfaces provide unprecedented control of the properties of light. By designing symmetry-breaking nanoholes in a metal sheet and engineering the optical properties of the metal using geometry, highly selective transmission and polarization control of light is obtained. To date such plasmonic filters have exhibited broad (>200 nm) transmission line widths in the NIR and as such are unsuitable for applications requiring narrow passbands, e.g., multispectral imaging. Here we present a novel subwavelength elliptical and circular nanohole array in a metallic film that simultaneously exhibits high transmission efficiency, polarization insensitivity, and narrow line width. The experimentally obtained line width is 79 nm with a transmission efficiency of 44%. By examining the electric and magnetic field distributions for various incident polarizations at the transmission peak we show that the narrowband characteristics are due to a Fano resonance. Good agreement is obtained between the experimental data, simulations, and analytical calculations. Our design can be modified to operate in other regions of the electromagnetic spectrum, and these filters may be integrated with suitable detectors such as photodiodes and single-photon avalanche diode arrays.