Tailorable spectral dispersion of copper-nickel 1D plasmonic crystals

Abstract

Plasmonic nanocomposites are a new class of materials that offers unprecedented opportunities to tailor the optical response, including the possibility to design their spectral and spatial dispersion at will. This includes the optical parameters rarely or never met in nature, which opens a path toward plasmonic metamaterials and the wide new area of transformation optics. Responsible for such a unique behavior are bound surface modes propagating along interfaces between materials with different signs of relative dielectric permittivity known as surface plasmon polaritons (SPP). Most metals possess negative relative permittivity in optical range due to the existence of free electron plasma. However, they also exhibit large absorption losses and are bound to a given spectral range defined by the metal itself, which is the reason why alternative plasmonic materials are being actively sought upon. One possible way to extend the toolbox of available materials is to use alternating metal-dielectric or metal-metal layers – the one-dimensional plasmonic crystals. Typically gold and silver are used for the metal part due to their large conductance and generally favorable properties. In this contribution we perform an analysis of the suitability of the use of copper for plasmonic nanocomposites. Its oxidation, the main barricade towards its more widespread use in plasmonics, is avoided by combining it with nickel. We utilize ab initio analysis by 2D finite element modeling and realistic material parameters to assess different electromagnetic modes. Tailorability of the response is attained by simple changing of the Cu to Ni fill factor. The analyzed CuNi plasmonic crystals are convenient for simple, low cost biochemical sensors and superabsorbers.