Tuning of Reciprocal Plasmonic Metasurface Resonances by Ultra-Thin Conformal Coatings

Micheal Mclamb,Glenn D Boreman,Tino Hofmann,Nuren Shuchi,Yanzeng Li,Victoria Paige Stinson,Serang Park

doi:10.3390/opt3010009

Micheal Mclamb, Glenn D Boreman + Show 5 more

Open Access

https://doi.org/10.3390/opt3010009

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Abstract

Metamaterials, in the form of perfect absorbers, have recently received attention for sensing and light-harvesting applications. The fabrication of such metamaterials involves several process steps and can often lead to nonidealities, which limit the performance of the metamaterial. A novel reciprocal plasmonic metasurface geometry composed of two plasmonic metasurfaces separated by a dielectric spacer was developed and investigated here. This geometry avoids many common fabrication-induced nonidealities by design and is synthesized by a combination of two-photon polymerization and electron-beam-based metallization. Infrared reflection measurements revealed that the reciprocal plasmonic metasurface is very sensitive to ultra-thin, conformal dielectric coatings. This is shown here by using Al2O3 grown by atomic layer deposition. It was observed experimentally that incremental conformal coatings of amorphous Al2O3 result in a spectral red shift of the absorption band of the reciprocal plasmonic metasurface. The experimental observations were corroborated by finite element model calculations, which also demonstrated a strong sensitivity of the reciprocal plasmonic metasurface geometry to conformal dielectric coatings. These coatings therefore offer the possibility for post-fabrication tuning of the reciprocal plasmonic metasurface resonances, thus rendering this novel geometry as an ideal candidate for narrow-band absorbers, which allow for cost-effective fabrication and tuning.

Highlights

Optical metamaterials are a group of engineered materials that are composed of an arrangement of artificial structures, which result in properties that are not exhibited in naturally occurring compounds [1,2]
We explored the optical response of reciprocal metasurfaces theoretically using finite element calculations and found that the geometry enables a post-fabrication adjustment of its spectral response by applying a thin conformal dielectric coating [24]
A second, much smaller reflection minimum, could be observed at 5.8 μm. This feature was due to an absorption band of IP-Dip, which was used as a dielectric spacer in the reciprocal plasmonic metasurface and can be recognized in the imaginary part of the dielectric function of the polymerized IP-Dip reported earlier [35]

Summary

Introduction

Optical metamaterials are a group of engineered materials that are composed of an arrangement of artificial structures, which result in properties that are not exhibited in naturally occurring compounds [1,2]. These unique optical properties can be used to produce extraordinary optical effects including giant optical activity [3,4], narrow band filters [5,6], perfect lensing [7,8], and perfect absorption [9,10], to name only a few of the most prominent, well-documented effects. In order to achieve perfect absorption, metamaterial designs that rely on heterostructures have shown promising results These materials are composed of multiple, stratified constituents [9,10,13–15,20–28]

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