Transverse energy flow and the "running" behaviour of the instantaneous field distribution of a light beam

Abstract

It is known that the orbital angular momentum of a paraxial beam is related to the rotational motion of the instantaneous field pattern representing the electric field optical-frequency oscillations [arXiv:0812.0888; J. Opt. A: Pure Appl. Opt 11, 094004, (2009)]. Now this conclusion is generalized: any identifiable directed motion of the instantaneous 2D pattern of the field oscillation ("running" behaviour of the instant oscillation pattern) corresponds to the transverse energy flow in the experimentally observable time-averaged field. The transverse orbital flow density can be treated as a natural geometric and kinematic characteristic of this running behaviour.