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Measurements of angular scattering due to surface roughness are taken from a 24-layer dielectric mirror and compared to theory. In addition, the top surface roughness of the multilayer stack is analyzed from Talystep profilometer measurements. This roughness data is used to obtain a spectral density function to be used in a vector multilayer scattering theory. When this is done, it is found that the theory, using the experimentally obtained roughness spectral density function, agrees remarkably well with the measured angular scattering data. This is especially true if care is taken to differentiate between particulate and roughness scattering. The theory uses three multilayer stack models to incorporate possible effects of different levels of correlation between interfaces of the stack. The stack was produced by Optical Coating Laboratory Incorporated.

Described here is the derivation of an expression designed to predict the angular distribution of light scattered from composite surfaces. The scattering is assumed to be the result of microroughness, either periodic or random, present at each interface of the composite surface. The theory retains the vector nature of the fields and allows complex optical constants. The angles of incidence and scattering or diffraction are arbitrary. The number and thicknesses of the layers in the composite surface are arbitrary. The primary restriction on the validity of the theory is that the incident wavelength λ >>δ where δ represents the root mean square (rms) roughness of any interface. This restriction therefore precludes the application of this theory to high-efficiency gratings. However, low-efficiency gratings, such as those designed for beam sampler applications, fall within the validity of the theory. Also, high quality optical components, such as laser gyro mirrors, typically have rms roughness values much less than a wavelength. Various aspects and applications of this theory have been published previously.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Outlined here is a derivation of the Rayleigh-Fano equations and how they may be applied to light scattering from periodic and random surface irregularity.© (1981) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.

Angle resolved scattering of synchrotron radiation incident on optical surfaces has been measured in the energy range from 75-750 eV. The scattering was measured in the plane of incidence, typically from 3 degrees to at least 40 degrees from the specular direction, with an angle of incidence of 84 degrees from the surface normal. The incident radiation was polarized either parallel or perpendicular to the plane of incidence, but the polarization state of the scattered radiation was not measured. Polished and diamond-turned optical surfaces were studied. The diamond-turned surfaces were turned with an interrupted cut, and measurements were taken with the direction of the grooves both parallel and perpendicular to the plane of incidence. The three diamond-turned surfaces were Cu, electroless Ni on Cu, and electroplated Au on electroless Ni on Cu. The polished samples included evaporated Au on a sapphire substrate.