title: Quantitative measurement of the orbital angular momentum density of light.
abstract: In this work we derive expressions for the orbital angular momentum (OAM) density of light, for both symmetric and nonsymmetric optical fields, that allow a direct comparison between theory and experiment. We present a simple method for measuring the OAM density in optical fields and test the approach on superimposed nondiffracting higher-order Bessel beams. The measurement technique makes use of a single spatial light modulator and a Fourier transforming lens to measure the OAM spectrum of the optical field. Quantitative values for the OAM density as a function of the radial position in the optical field are obtained for both symmetric and nonsymmetric superpositions, illustrating good agreement with the theoretical prediction.
authors.affiliation: Council for Scientific and Industrial Research National Laser Centre, P.O. Box 395, Pretoria 0001, South Africa.
authors.forename: Angela
authors.initials: A
authors.lastname: Dudley
authors.forename: Igor A
authors.initials: IA
authors.lastname: Litvin
authors.forename: Andrew
authors.initials: A
authors.lastname: Forbes