http://dx.doi.org/10.1038/srep06386">
 

Document Type

Journal Article

Department/Unit

Department of Physics

Title

Negative optical torque

Language

English

Abstract

Light carries angular momentum, and as such it can exert torques on material objects. Applications of these opto-mechanical effects were limited initially due to their smallness in magnitude, but later becomes powerful and versatile after the invention of laser. Novel and practical approaches for harvesting light for particle rotation have since been demonstrated, where the structure is always subjected to a positive optical torque along a certain axis if the incident angular momentum has a positive projection on the same axis. We report here an interesting phenomenon of "negative optical torque", meaning that incoming photons carrying angular momentum rotate an object in the opposite sense. Surprisingly this can be realized quite straightforwardly in simple planar structures. Field retardation is a necessary condition and discrete rotational symmetry of material object plays an important role. The optimal conditions are explored and explained.

Publication Date

2014

Source Publication Title

Scientific Reports

Volume

4

Start Page

6386

Publisher

Nature Publishing Group

ISSN (print)

20452322

ISSN (electronic)

20452322

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