Abstract

The method of generalized rays is shown to be a convenient framework for the study of the propagation of partially coherent beams in square-law media. Both on-axis and off-axis paraxial propagations are considered. Propagation characteristics of Gaussian Schell-model beams are completely worked out as an example, taking full advantage of the SL(2,R) group underlying the problem.¹ All the invariants are worked out and interpreted. The degree of global coherence is one of the invariants. It is shown that every square-law medium has a characteristic one-parameter family of isotropic Gaussian Schell-model beams and a two-parameter family of anisotropic Gaussian Schell-model beams as its normal modes. This includes a new class of striplike modes. Our results are compared with the familiar results for the propagation of coherent Gaussian beams in such media.

© 1987 Optical Society of America