Abstract

The field distribution of Laguerre-Gaussian laser modes has a phase which depends on the azimuthal angle, ϕ, of the form ϕ, where ϕ = 0, ± 1, ± 2, = 3 etc. It has been shown by Allen et al. that this azimuthal phase dependence gives rise to a well defined orbital angular momentum which corresponds to ϕ per photon in the mode. As is well known, circularly polarised light also carries an angular momentum associated with the photon spin corresponding to ϕ per photon. Recent work by He et al. [2] has shown qualitatively that angular momentum can be transferred from a linearly polarised Laguerre-Gaussian mode to an optically trapped ceramic or metal oxide particle. However, their work does not prove that orbital angular momentum is well defined at ϕ per photon. We report progress in, what we believe to be, the first experimental confirmation that the orbital angular momentum of a linearly polarised Laguerre-Gaussian mode is indeed ϕ per photon.

© 1996 Optical Society of America