Phase-space inequality for partially coherent optical beams

A phase-space inequality is derived for beams of arbitrary state of spatial coherence. It applies to the product of a factor which expresses the effec tive coherence area of the source that generates the beam and the effective angular spread of the beam; and, by analogy with coherent beams, it may be regarded as a measure of the beam quality. It is found that the factor att ains a minimum for the entire class of Gaussian Schell-model beams (which i nclude the Hermite Gaussian laser mode). (C) 2001 Elsevier Science B.V. All rights reserved.