Bismuth-based gap-plasmon metasurfaces for visible photonics with volatile tuning potential

Abstract

Gap-plasmon metasurfaces based on metal-insulator-metal (MIM) nanostructures have been extensively employed over the last years, as they provide a versatile design platform for local and/or global control of the amplitude, phase and polarisation of light from the visible to the THz domain [1]. However, current research in plasmonic metasurfaces lacks of good material building blocks, as the material choice is fundamentally limited to Ag, Au and Al [2]. Particularly in the visible spectrum, Ag and Al are the preferred (and the only realistic) option towards the development of MIM metasurfaces, as they suffer from lower plasmonic losses with respect to other metallic elements. Recently, bismuth-based nanostructures have been proved as an excellent material for plasmonics in the ultraviolet and visible [3] , [4] , [5]. However, its use in MIM metasurfaces for the visible spectrum remains largely unexplored. Furthermore, bismuth exhibits a relatively low melting temperature (~270 °C), with its solid-to-liquid phase transition being accompanied by significant changes in its permittivity function [6]. This potentially paves the way for active plasmonics [7].