Abstract

Past studies have determined that fully coherent beams undergo nonspecular changes on reflection by multilayered media. These changes involve lateral, focal, and angular shifts of the beam axis and a magnification of the beamwidth.¹ By using Gaussian Schell-model beams, we examine such nonspecular effects in the case of partly coherent beams. We find that only the angular shift is affected by the presence of incoherence, while the other three nonspecular effects are identical to those in coherent Gaussian beams having the same beam-waist size. On the other hand, we show that the coherence length, the far-field diffraction angle, and the degree of global coherence are also changed by the reflection process. However, all these nonspecular changes are correlated so that the degree of global coherence multiplied by the far-field diffraction angle yields a factor that is preserved as an invariant quantity by the reflection process.

© 1988 Optical Society of America