Experimental studies of inhomogeneous coatings for optical applications

Abstract

A novel codeposition process has been developed for the fabrication of inhomogeneous optical coatings. These single-layer coatings exhibit composition and refractive index that vary continuously with thickness. Two types of inhomogeneous optical filters for antireflection and narrow band rejection applications, respectively, were experimentally fabricated using different vacuum deposition processes. The antireflection coating, composed of ZrO2 and MgF2, was prepared by electron beam coevaporation. The narrow band rejection filter, made up of SiO2 and TiO2, was codeposited by ion assisted, dual ion beam sputtering technique. The physical, chemical, and microstructural characteristics, as well as optical and environmental properties of these filters were evaluated.

Design and fabrication of a combined three‐layer coating including gradient refractive index films for broadband antireflection on silicon

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Spectroscopic ellipsometry characterization of thin film photovoltaic materials and devices

“…Here, it is clear that the top of the layer has a lower refractive index, and is less dense than the bottom of the layer, which has a higher refractive index. Hence, the overall refractive index is decreasing when moving from the bottom of the layer to the top of the layer, which is the standard index grading profile for AR coatings [1]- [3]. Ellipsometry can also be used to determine film thicknesses, which can then be optimized for maximum performance.…”

Pulse magnetron sputtering in a reactive gas mixture of variable composition to manufacture multilayer and gradient optical coatings

“…New design possibilities are given by gradient layers, where the refractive index gradually changes with film thickness. Such gradient films are beside CVD techniques [1] deposited by either cosputtering [2] or co-evaporation [3] of two materials with different refractive indexes like SiO 2 and TiO 2 .…”