Silver nanorings metasurface for enhanced absorption at optical frequencies
Résumé
Plasmonic nanoparticles are key to the realization of selective light absorbers, and especially metallic nanoparticles that exhibit tunable optical properties with implications in multiple fields such as photovoltaic, photodetectors and optical filters [1]. Among those nanoparticles, metallic split-ring resonators are metamaterials with optically induced magnetic responses allowing unique possibilities for controlling light and enhance absorption in the visible and near IR domains depending on their geometric parameters. The objective of this research is to show the enhancement of absorption at optical frequencies by not only designing a metasurface made of silver split-rings with realistic geometric parameters but also providing a first proof of concept of those tunable circular nanorings entirely made by scalable bottom-up approaches. First, Finite Difference Time Domain (FDTD) simulations were performed to optimize the silver nanoring geometric properties thanks to a parametric study (inner, outer diameters, thickness, split-ring gap, array periodicity). This showed full control on resonance peaks and absorbance enhancement in the visible and near IR. Next, we showed the realization of circular silver split-ring arrays on a large area via bottom-up techniques. Silver single-crystalline nanocubes (synthesized in solution via the polyol process) were self-assembled in Polydimethylsiloxane (PDMS) templates previously nanostructured with a pre-defined split-ring motif. Epitaxial nanowelding techniques at low temperature [2] were then employed to connect the individual nanocubes together to obtain a continuous quasi-monocrystalline material.
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