Elsevier

Metamaterials

Volume 2, Issue 1, May 2008, Pages 45-51
Metamaterials

Plasmonic nanoantenna arrays for the visible

https://doi.org/10.1016/j.metmat.2008.03.001Get rights and content

Abstract

Gold nanoantenna arrays composed of paired elliptical cylinders are fabricated and studied experimentally and numerically. The arrays show far-field spectra resonances in the visible range for two orthogonal polarizations. Finite element method is used to accurately simulate the far-field spectra with modified gold optical properties. The resonance wavelengths and electrical field enhancement are studied as functions of the antenna dimensions. The field enhancement is found to be inversely proportional to the gap size.

Section snippets

Experimental details

Two samples of paired gold nanoantenna arrays, named A and B, were designed and fabricated. The arrays are composed of gold nanoparticles with elliptic cylinder shapes. Each unit cell has two nanoparticles with a gap between the two particles along their major axes (Fig. 1(a)). The periods along the major and minor axes are 400 and 200 nm, respectively. The fabrication process is as follows: a quartz substrate is first spin-coated with the positive e-beam resist ZEP520A, and a 20-nm-thick film

Simulation results and discussion

A FEM model was created using a commercial package (COMSOL Multiphysics) to simulate the electrodynamics of the nanoantenna arrays. The dielectric constants of gold were obtained from literature [32]. The dimensions of the major axis, the minor axis, and the gap in the FEM models were tuned in order to match the simulated resonance wavelengths to the experimental results, and the resulting dimensions used in simulations are as follows: for sample A, the major axis is 110 nm, minor axis 55 nm, and

Conclusions

We have demonstrated that FEM simulations can accurately model the far-field spectra of optical nanoantenna arrays in the visible range if material property modification for fabricated nanostructures as compared to bulk data is taken into account. For the optical nanoantenna arrays composed of paired gold elliptical cylinders, the resonant wavelength red-shifts with an increase of the nanoparticle major axis and blue-shifts with an increase of the minor axis. Decreasing the gap also red-shifts

Acknowledgements

This work is supported in part by ARO-STTR award W911NF-07-C-0008. A. B. acknowledges support from the Danish Research Agency (NABIIT programme committee, grant 2106-05-0033). The authors wish to thank Samuel Gresillon at CNRS and Universite Pierre et Marie Curie Paris 6 for many fruitful discussions and Mark Stockman at Georgia State University for discussions on the field-gap relation.

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