3D coaxial out-of-plane metallic antennas for filtering and multi-spectral imaging in the infrared range.

Andrea Jacassi,Francesco Tantussi,Francesco De Angelis,Angelo Bozzola,Pierfrancesco Zilio

doi:10.1038/srep28738

Andrea Jacassi, Francesco Tantussi + Show 3 more

Open Access

https://doi.org/10.1038/srep28738

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Abstract

We fabricated and investigated a new configuration of 3D coaxial metallic antennas working in the infrared which combines the strong lateral light scattering of vertical plasmonic structures with the selective spectral transmission of 2D arrays of coaxial apertures. The coaxial structures are fabricated with a top-down method based on a template of hollow 3D antennas. Each antenna has a multilayer radial structure consisting of dielectric and metallic materials not achievable in a 2D configuration. A planar metallic layer is inserted normally to the antennas. The outer dielectric shell of the antenna defines a nanometric gap between the horizontal plane and the vertical walls. Thanks to this aperture, light can tunnel to the other side of the plane, and be transmitted to the far field in a set of resonances. These are investigated with finite-elements electromagnetic calculations and with Fourier-transform infrared spectroscopy measurements. The spectral position of the resonances can be tuned by changing the lattice period and/or the antenna length. Thanks to the strong scattering provided by the 3D geometry, the transmission peaks possess a high signal-to-noise ratio even when the illuminated area is less than 2 × 2 times the operation wavelength. This opens new possibilities for multispectral imaging in the IR with wavelength-scale spatial resolution.

Highlights

IntroductionSeveral photonic[27,28,29] and plasmonic[14,15,30,31,32,33,34] filters have been proposed during the last decade
To overcome this limitation, several photonic[27,28,29] and plasmonic[14,15,30,31,32,33,34] filters have been proposed during the last decade
It consists of an array of 3D coaxial antennas with a multilayer structure along the radial direction

Summary

Introduction

Several photonic[27,28,29] and plasmonic[14,15,30,31,32,33,34] filters have been proposed during the last decade These are based on periodic arrangements of nanoscale apertures, and the wavelength tuning can be done by changing the lattice period of the array. The nanometric gap between the antenna and the metallic mid-plane allows the flow of light to the other side of the sample in a set of well-defined resonances. Their spectral position and bandwidth can be tuned by controlling the geometrical parameters of the structure. More details on the numerical calculations, on the impact of the geometrical parameters of the array and on the parasitic absorption in the IR range are presented in the Supplementary Information

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Conclusion