Mechanical equivalence of spin and orbital angular momentum of light: An optical spanner

N. B. Simpson, K. Dholakia, L. Allen, M. J. Padgett

Research output: Chapter in Book/Report/Conference proceedingChapter


We use a Laguerre-Gaussian laser mode within an optical tweezers arrangement to demonstrate the transfer of the orbital angular momentum of a laser mode to a trapped particle. The particle is optically confined in three dimensions and can be made to rotate; thus the apparatus is an optical spanner. We show that the spin angular momentum of ±h per photon associated with circularly polarized light can add to, or subtract from, the orbital angular momentum to give a total angular momentum. The observed cancellation of the spin and orbital angular momentum shows that, as predicted, a Laguerre-Gaussian mode with an azimuthal mode index 1 = 1 has a well-defined orbital angular momentum corresponding to h per photon.

Original languageEnglish
Title of host publicationOptical Angular Momentum
PublisherCRC Press
Number of pages3
ISBN (Electronic)9781482269017
ISBN (Print)9780750309011
Publication statusPublished - 2016 Apr 19

Bibliographical note

Publisher Copyright:
© 2003 by Taylor & Francis Group, LLC.

All Science Journal Classification (ASJC) codes

  • Engineering(all)
  • Physics and Astronomy(all)


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