Abstract
With the rapid advances of functional dielectric metasurfaces and their integration on on-chip nanophotonic devices, the necessity of metasurfaces working in different environments, especially in biological applications, arose. However, the metasurfaces’ performance is tied to the unit cell’s efficiency and ultimately the surrounding environment it was designed for, thus reducing its applicability if exposed to altering refractive index media. Here, we report a method to increase a metasurface’s versatility by covering the high-index metasurface with a low index porous SiO2 film, protecting the metasurface from environmental changes while keeping the working efficiency unchanged. We show, that a covered metasurface retains its functionality even when exposed to fluidic environments.
Highlights
Metamaterials are artificially designed structures whose optical properties do not primarily arise from the choice of material itself but rather from the design and distribution of so called single meta-atoms
All-dielectric metasurfaces benefit from applications that work in transmission and their efficiency is determined by the single unit cell that consists of high-index nanostructures in a low-index environment [21,22]
We present a method to protect a dielectric metasurface from the influence of a changing environment by coating the sample in a porous SiO2-film
Summary
Metamaterials are artificially designed structures whose optical properties do not primarily arise from the choice of material itself but rather from the design and distribution of so called single meta-atoms. Most meta-atom designs are rendered suboptimal if transferred to another refractive index environment and would need to be redesigned to work properly To illustrate this effect, we calculated the transmission of a typically geometric-phase metasurface made of silicon nanofins on a glass substrate for different refractive index values of the surrounding host material nH. We calculated the transmission for both circular states whereas co-polarization signifies the same helicity as the incident light and cross-polarization represents the converted polarization that carries the desired phase information Both the transmitted co- and crosspolarization change significantly with the refractive index of the environment reducing the metasurface’s efficiency, e.g., the ability to alter the phase of the transmitted light in geometricphase metasurfaces (see Fig. 1a).
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