Negative optical torque

Jun Chen, Tsz Fai Jack NG, Kun Ding, Kin Hung Fung, Zhifang Lin, C. T. Chan*

*Corresponding author for this work

Research output: Contribution to journalJournal articlepeer-review

56 Citations (Scopus)
46 Downloads (Pure)


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.

Original languageEnglish
Article number6386
JournalScientific Reports
Publication statusPublished - 2014

Scopus Subject Areas

  • General


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