Coherence vortices in partially coherent beams

It is demonstrated that the spectral degree of coherence of a partially coherent beam may possess isolated pairs of points at which its phase is singular, and that in the neighborhood of these points the phase may possess a vortex structure. Partially coherent beams consisting of Hermite-Gaussian modes are considered as an example. The physical consequences of these so-called coherence vortices are discussed. (C) 2003 Elsevier Science B.V. All rights reserved.