Gain-Assisted Optical Pulling Force on Plasmonic Graded Nano-Shell with Equivalent Medium Theory

Yamin Wu,Yang Huang,Lei Gao,Pujuan Ma

doi:10.3390/physics3040060

Yamin Wu, Yang Huang + Show 2 more

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https://doi.org/10.3390/physics3040060

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Abstract

The tunable optical pulling force on a graded plasmonic core-shell nanoparticle consisting of a gain dielectric core and graded plasmonic shell is investigated in the illumination of a plane wave. In this paper, the electrostatic polarizability and the equivalent permittivity of the core-shell sphere are derived and the plasmonic enhanced optical pulling force in the antibonding and bonding dipole modes of the graded nanoparticle are demonstrated. Additionally, the resonant pulling force occurring on the dipole mode is shown to be dependent on the aspect ratio of the core-shell particle, which is illustrated by the obtained equivalent permittivity. This shows that the gradation of the graded shell will influence the plasmonic feature of the particle, thus further shifting the resonant optical force peaks and strengthening the pulling force. The obtained results provide an additional degree of freedom to manipulate nanoparticles and give a deep insight into light–matter interaction.

Highlights

Force on Plasmonic Graded Nano-The change of the field gradients or linear momentum carried by photons will give rise to the optical force [1]
One of the goals in this study is to demonstrate the different behaviors of the optical force in plasmonic resonant modes of a graded nanoshell with different aspect ratios (i.e., a/b) on the same level of gain
In this paper, giant gain-assisted resonant pulling forces are demonstrated on a graded core-shell nanoparticle in a long-wavelength approximation

Summary

Introduction

Force on Plasmonic Graded Nano-The change of the field gradients or linear momentum carried by photons will give rise to the optical force [1]. Radiation pressure induced by photon momentum exchange always pushes objects in the light flow direction, which is known as “optical pushing”. The optical pulling force is a more novel phenomenon than the pushing one because it requires many more critical conditions to realize it and has many more potential applications in nano-manipulation [2,3,4,5,6,7,8]. The optical pulling forces acting on a nano-object consisting of chiral [12,13,14], hyperbolic [15], and gain [16,17,18] materials have been widely investigated

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