It is well known today that scattering phenomena in multilayer coatings are of great importance, and we have already shown how and why it was necessary to understand this mechanism in detail if we want to increase the performances of optical systems. Among the numerous parameters involved in the calculation of the scattered waves (roughnesses, autocorrelation lengths, cross-correlation coefficients, indices, and thicknesses of the layers, etc.), the cross-correlation laws inside the stack are essential, because they are largely responsible for the form and the magnitude of the flux scattered from a coating. Moreover, knowing these laws provides us with valuable information concerning the grain structure of thin-film materials. First we show how some specific effects (such as the antiscattering effect) permit us to determine the cross-correlation laws in the case of a coating with a small number of layers and how a carefully done comparison between theory and experiment can be used to characterize the grain size of materials. In the case of a coating with many layers, the phenomena are obviously more complicated to interpret. Nevertheless, an investigation is possible (using an aluminum-layer technique), and we present our results for a mirror.
© 1987 Optical Society of AmericaFull Article | PDF Article
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