3D vertical nanostructures for enhanced infrared plasmonics.

Mario Malerba,Ermanno Miele,Michele Dipalo,Pierfrancesco Zilio,Gabriele C Messina,Remo Proietti Zaccaria,Francesco De Angelis,Maddalena Patrini,Daniele Bajoni,Alessandro Alabastri,Andrea Toma

doi:10.1038/srep16436

Mario Malerba, Ermanno Miele + Show 9 more

Open Access

https://doi.org/10.1038/srep16436

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Abstract

The exploitation of surface plasmon polaritons has been mostly limited to the visible and near infrared range, due to the low frequency limit for coherent plasmon excitation and the reduction of confinement on the metal surface for lower energies. In this work we show that 3D - out of plane - nanostructures can considerably increase the intrinsic quality of the optical output, light confinement and electric field enhancement factors, also in the near and mid-infrared. We suggest that the physical principle relies on the combination of far field and near field interactions between neighboring antennas, promoted by the 3D out-of-plane geometry. We first analyze the changes in the optical behavior, which occur when passing from a single on-plane nanostructure to a 3D out-of-plane configuration. Then we show that by arranging the nanostructures in periodic arrays, 3D architectures can provide, in the mid-IR, a much stronger plasmonic response, compared to that achievable with the use of 2D configurations, leading to higher energy harvesting properties and improved Q-factors, with bright perspective up to the terahertz range.

Highlights

In-phase, giving rise to a grating effect[38,39,40,41,42]
In this work we show that passing from conventional 2D to 3D architectures enables stronger plasmonic response, longer lifetime, higher harvesting capabilities, and higher field enhancements in the IR region
Despite the apparent flaw of triggering the plasmonic response in planar structures with a non-vertical wave vector, the choice of tilting the source for both arrangements allows a fair comparison of scattering and extinction cross-sections

Summary

Introduction

In-phase, giving rise to a grating effect[38,39,40,41,42]. This constructive interference is known to produce collective plasmon excitations with narrower resonances and higher local electric fields, partially overcoming the mentioned limitations of plasmonics in the IR regions. In this work we show that passing from conventional 2D to 3D architectures enables stronger plasmonic response, longer lifetime, higher harvesting capabilities, and higher field enhancements in the IR region Both with numerical calculations and with experimental characterizations, we suggest that the physical principle relies on the combination of far field and near field interactions between neighbouring antennas, and that this is abet by the out-of-plane geometry. To better explain these concepts, we first analyse the changes in the optical behaviour that occur when passing from a single on-plane nanostructure to a 3D out-of-plane nanostructure. We show that by arranging the nanostructures in periodic arrays (grating effect), 3D architectures intrinsically promote a much stronger plasmonic response, compared to that achievable with the use of 2D configurations, even in the mid-IR

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