Optical vortex

When projected onto a flat surface, an optical vortex looks like a ring of light, with a dark hole in the center.

This spinning carries orbital angular momentum with the wave train, and will induce torque on an electric dipole.

The phase in the field circulates around these points of zero intensity (giving rise to the name vortex).

Integrating the phase of the field around a path enclosing a vortex yields an integer multiple of 2π.

An optical vortex, being fundamentally a phase structure, cannot be detected from its intensity profile alone.

There are a broad variety of applications of optical vortices in diverse areas of communications and imaging.

Diagram of different modes, four of which are optical vortices. Columns show the helical structures, phase-front and intensity of the beams
A Laguerre-Gaussian beam is an optical vortex with a line singularity along the beam axis
Vortices created by CGH
An interference pattern of a vortex beam with an inclined plane wave, results in a fork-like interferogram