Restricting Orbital Angular Momentum by Transverse Coherence
Ronald L. Cappelletti, John T. Vinson
A traveling wave or wave packet may possess orbital angular momentum in the form of a phase vortex about its axis of propagation. These orbital angular momentum states are a general wave phenomenon, and, as such, can be realized for individual wave packets or in a wave of unstructured particles or the continuum in between. Such waves can be generated by various techniques, including by passing an unstructured wave through a vortex phase plate. The generation of single-particle vortex states with this technique is reliant on each particle adequately sampling the area of the vortex plate. If the transverse restriction of the wave incident upon the plate is such as to completely occlude illumination of the discontinuity at the center of the vortex phase plate, the probability of detecting a single particle having a unit of orbital angular momentum vanishes. Here we examine this effect using laser light and consider the implications for interactions using orbital angular momentum beams of light or matter.