Transverse rotation of the momentary field distribution and the orbital angular momentum of a light beam
arXiv:0812.0888 · doi:10.1088/1464-4258/11/9/094004
Abstract
The transverse beam pattern, usually observed in experiment, is a result of averaging the optical-frequency oscillations of the electromagnetic field distributed over the beam cross section. An analytical criterion is derived that these oscillations are coupled with a sort of rotation around the beam axis. This criterion appears to be in direct relation with the usual definition of the beam orbital angular momentum.
9 pages, 1 figure with animation