Optical Twist Induced by Plasmonic Resonance.

Jun Chen,Jack Ng,Liyong Cui,Neng Wang,Zhifang Lin,Xiao Li

doi:10.1038/srep27927

Abstract

Harvesting light for optical torque is of significant importance, owing to its ability to rotate nano- or micro-objects. Nevertheless, applying a strong optical torque remains a challenging task: angular momentum must conserve but light is limited. A simple argument shows the tendency for two objects with strong mutual scattering or light exchange to exhibit a conspicuously enhanced optical torque without large extinction or absorption cross section. The torque on each object is almost equal but opposite, which we called optical twist. The effect is quite significant for plasmonic particle cluster, but can also be observed in structures with other morphologies. Such approach exhibits an unprecedentedly large torque to light extinction or absorption ratio, enabling limited light to exert a relatively large torque without severe heating. Our work contributes to the understanding of optical torque and introduces a novel way to manipulate the internal degrees of freedom of a structured particle cluster.

Highlights

Harvesting light for optical torque is of significant importance, owing to its ability to rotate nano- or micro-objects
The exact value of the torque can be different between our structure and the realistic ones, the aim here is to demonstrate the possibility of achieving large torque without increasing the laser power
We investigated the optical twist in two-particle-cluster structures

Summary

Introduction

Harvesting light for optical torque is of significant importance, owing to its ability to rotate nano- or micro-objects. The effect is quite significant for plasmonic particle cluster, but can be observed in structures with other morphologies Such approach exhibits an unprecedentedly large torque to light extinction or absorption ratio, enabling limited light to exert a relatively large torque without severe heating. Last but not least, compared with direct light illumination, a metallic structure is able to shape the light beam to exert torque on a dielectric object in a much more effective manner. This will add more possibilities for optical manipulation

Methods

Results

Conclusion