Optical properties of thin film Au-MgF2 cermets

The preparation of thin films of cermets of gold in magnesium fluoride and the ellipsometric determination of the optical constants of the materials of the films are described. The results for materials of two compositions are compared with predictions based on the Maxwell Garnett expression for the complex refractive index of cermets in terms of the refractive indices of the constituents. It is shown that reasonable agreement between experimentally determined and theoretical values of the refractive indices of the cermets can be approached only if the restriction of the mean free paths of the conduction electrons in the gold particles is taken into account.     

The design,preparation and optical measurement of thin film polarizers

The general approach to the design of thin film polarizers is outlined by reference to the principle of equivalent layers, and an analytical expression is derived for the number of quarter-wave layers required in a mirror structure to provide a specified polarization transmittance ratio $\text{(ifP =}\text{T}{}_{\mathrm{?}}\text{T}{}_{\mathrm{\perp }}\text{)}$. It is shown that the high polarization ratio and the small sensitivity of this parameter to the angle of incidence are conflicting specifications which require a compromise solution in practice. Also, to achieve simple and precise monitoring of the optical properties of the layers during deposition, double half-wave filter systems are shown to be preferable to multilayer quarter-wave mirrors as polarizers.The results of measurements on double half-wave polarizers for use with large aperture Pockel's cell shutters and Faraday isolators in high power neodymium glass lasers are presented with particular reference to transmittance, polarization ratio, superficial unifromity and laser damage threshold.     

Optical properties of narrow-band spectral filter coatings related to layer structure and preparation

The optical properties of thirty-five all-dielectric spectral filter coatings for the visible spectrum have been investigated and correlated with the deposition conditions of the constituent layers of cryolite and zinc sulfide and with the processes which occur when the coatings are exposed to atmosphere. It will be shown that the results of measurements of transmittance and reflectance over the passband wavelengths can be predicted theoretically only if account is taken of absorption in the layers and scattering at the rough boundaries and of changes in the refractive indices of the layers due to water penetration.     

Orientation of magnetic particles in a recording medium

The theory of the motion of magnetic particles in a viscous Newtonian medium, first outlined by Newman and Yar-brough, has been extended to include both low and high field orientation modes. It is shown that the equations of motion can be solved analytically, i.e., without resort to numerical integration. The results of the analysis are used to predict values for easily measured parameters of recording media, such as the initial remanence ratio and squareness ratio.