Forward and Backward Unidirectional Scattering by the Core-Shell Nanocube Dimer with Balanced Gain and Loss.

Jingwei Lv,Chao Liu,Paul K Chu,Tao Sun,Qiang Liu,Haiwei Mu,Xiaoming Zhang,Xuntao Yu

doi:10.3390/nano10081440

Abstract

An optical nanoantenna consisting of a Au-dielectric core-shell nanocube dimer with switchable directionality was designed and described. Our theoretical model and numerical simulation showed that switching between forward and backward directions can be achieved with balanced gain and loss, using a single element by changing the coefficient κ in the core, which can be defined by the relative phase of the polarizability. The optical response indicated a remarkable dependence on the coefficient κ in the core as well as frequency. The location of the electric field enhancement was specified by the different coefficient κ and, furthermore, the chained optical nanoantenna and coupled electric dipole emitted to the optical nanoantenna played significant roles in unidirectional scattering. This simple method to calculate the feasibility of unidirectional and switchable scattering provides an effective strategy to explore the functionalities of nanophotonic devices.

Highlights

Metallic nanostructures featuring a multitude of localized and propagating surface plasmon resonances have attracted significant interest due to their ability to concentrate and manipulate light at the subwavelength scale [1,2]. Their extraordinary properties have been widely exploited in a broad range of optical applications, including solar cells [3,4], ultrasensitive sensors [5], photovoltaic devices [6,7], and so on
Optical nanostructures with hybrid active–passive geometries rely on the balance between gain and loss [13,14] and active–passive nanostructures shed light on important non-Hermitian quantum mechanics
The far-field forward-to-backward directionality of the core-shell nanocube dimer with balanced gain and loss in dB can be obtained by GFS/BSmax = 10 log10(SF/SB), where SF is the amplitude of the power radiated in the forward (x > 0) and backward (x < 0) directions [34,35]

Summary

Introduction

Metallic nanostructures featuring a multitude of localized and propagating surface plasmon resonances have attracted significant interest due to their ability to concentrate and manipulate light at the subwavelength scale [1,2]. Their extraordinary properties have been widely exploited in a broad range of optical applications, including solar cells [3,4], ultrasensitive sensors [5], photovoltaic devices [6,7], and so on. The unidirectional scattering properties of the core-shell nanocube dimer with balanced gain and loss arranged in a chain were determined and directional emission from the electric dipole emitter was demonstrated

Theory

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