Unidirectional broadband radiation of honeycomb plasmonic antenna array with broken symmetry

Rüştü Umut Tok,Kürşat Şendur,Cleva Ow-Yang

doi:10.1364/oe.19.022731

Abstract

Emerging plasmonic and photovoltaic applications benefit from effective interaction between optical antennas and unidirectional incident light over a wide spectrum. Here, we propose a honeycomb array of plasmonic nanoantennas with broken symmetry to obtain a unidirectional radiation pattern over a wide spectrum. The honeycomb nanoantenna array is based on a hexagonal grid with periodically arranged nanostructure building blocks. To analyze the far-field optical distribution and spectral behavior of the plasmonic antenna honeycomb, a two-dimensional Wigner-Seitz unit cell is used together with periodic boundary conditions. As a result of the vectoral superposition of the fields produced by the Wigner-Seitz unit cells, far-zone optical fields interfere constructively or destructively in different directions. The constructive interference along the array's normal direction engenders unidirectional radiation. Due to the broken symmetry of the Wigner-Seitz cell, multiple resonances are supported by the plasmonic antenna honeycomb array over a broad spectrum.

Highlights

Optical nanoantennas have fascinated scientists because of their ability to manipulate light beyond the diffraction limit [1, 2]
To address the need for a unidirectional antenna pattern with a wide spectral response, we propose a honeycomb array of plasmonic nanoantennas with broken symmetry
The far-zone radiation of a single isolated optical nanoantenna is determined by the antenna geometry, its material properties, and the excitation properties including wavelength and polarization, the effects of which have been extensively studied in the literature [1, 2]

Summary

Introduction

Optical nanoantennas have fascinated scientists because of their ability to manipulate light beyond the diffraction limit [1, 2] Such an achievement at the nanoscale has enabled scientists to overcome technological barriers and expand the frontiers for scientific breakthroughs in nearfield imaging [3], solar cells [4], nanolithography [5], optical data storage [6], heat assisted magnetic recording [7], light emitting devices [8], spectroscopy [9], medical applications [10], and bio-chemical sensors [11]. Optical antennas with unidirectional far-zone radiation patterns have important implications for photovoltaic devices, in which antennas have been utilized to improve the energy conversion efficiency [4, 12]. One important factor that needs to be addressed to improve the performance efficiency is the mismatch between the directionality of the incident

Methods

Results

Conclusion