Abstract

This paper reports the direct observation of secondary scattering resulting from guided scattered light within a multilayer coating. In other words, the distribution and level of the light scattered by the coating is such that a significant fraction of this light is scattered into guided modes of the film. Because such guided light is trapped within the coating, it propagates within the coating until it is either absorbed or scattered a second time. The secondary scatter is observed at a significant distance from the point of incidence of the initial beam of light. Although we believe that the dramatic nature of the observations presented here results from a unique combination of experimental factors, this effect may be present in a variety of practical thin-film coatings. Perhaps even more interesting is the clear evidence that the secondary scatter observed demonstrates clearly that the primary scattered light is distributed in a dipole radiation pattern, corresponding to Rayleigh scattering from subwavelength-sized scatter sites.

© 1992 Optical Society of America