Many applications are emerging that require optical coatings with the ability to withstand high fluence and that at the same time possess very low scatter and absorption loss while demonstrating resistance to environmental influences. Optical coatings fabricated with the ion beam sputtering (IBS) process possess these characteristics. This paper provides an overview of the optical and mechanical characteristics of IBS coatings and compares their laser damage threshold characteristics to coating fabricated with electron beam (e-beam) and ion assisted electron beam (IAD) techniques.
Adequate modeling of high quality non-absorbing dielectric thin films requires the inclusion of the degree of bulk inhomogeneity as one of the parameters in the model describing the film. We show that in the case of a satisfactory choice of a thin film model, the main source of errors in the computed optical parameters of high quality films are systematic errors in spectrophotometric data. Based on practical examples and theoretical predictions we estimate that an accuracy of 0.5% in the determination of optical parameters of dielectric thin films should be considered as a good result when viewed in the context of the current state of the art in optical characterization based on spectrophotometric data. A level of accuracy significantly better than this would require an extraordinary effort.
The shape of the angular and spectral reflection curves of depth-graded x-ray multilayer mirrors may be controlled by the proper variation of the layer thicknesses. The determination of the thickness distribution of the layers that gives the best possible approximation to the desired reflection curve profile is a complicated mathematical problem. The present work reports on the application of the needle variations method to the design of graded x-ray multilayer mirrors in both angular and spectral domain.
We demonstrate that the needle optimization technique enables the effective design of optical coatings for applications which require a specific spectral response over a wide angular range. A preliminary choice of the most useful layer materials is discussed in connection with the question of the design optimality. It is shown that in many cases two-material designs with the lowest and highest accessible refractive index values are optimal from a practical point of view. It is also shown that in some cases intermediate refractive index values are quite necessary to achieve a good approximation of design targets.
The design of polarization insensitive optical coatings via use of the needle synthesis algorithm in combination with second order optimization methods is explored. Several designs produced with this technique are presented and comparisons are made with the results of other design techniques drawn from the literature.
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