Unified theory of coherence and polarization of random electromagnetic beams

The usual treatment of polarization of randomly varying electromagnetic waves is based on the well-known Stokes parameter or, equivalently, on 2 x 2 coherence matrices (also called polarization matrices). Neither of them is adequate to elucidate the recently discovered changes of the state of polarization which a light beam may undergo as the beam propagates. We present a unified theory of coherence and polarization of random electromagnetic beams which brings out clearly the intimate relationship which exists between these two phenomena and which makes it possible to predict the changes in the state of polarization of a partially coherent electromagnetic beam on propagation. We illustrate the analysis by showing that a completely unpolarized beam may be spatially fully coherent. (C) 2003 Elsevier Science B.V. All rights reserved.