Analysis and control of light scattered by optical components for space applications

Abstract

Space applications require more and more demanding optical functions. This evolution led to the development of new generation of optical components with extreme performances in terms of scattering level, roughness, localized defects, spectral evolution of performances, coherent backscattering…. In this context, optical components produced for space applications present an increasing complexity with extreme specifications. As a consequence, new problematics specific to this generation of components appeared and among these, the management of light scattered by these components remains a significant challenge. For example, for complex optical coatings (typically with more than 100 interfaces), the scattering response of the component is not directly correlated to the substrate spectrum, as it is the case for simple coatings (less than 40 layers). For this reason, an accurate modelling of light scattered by complex optical coatings requires a global analysis taking into account different parameters from the design and manufacturing to the conditions of use of the component. We will present in this paper the last developments performed by the Scattering Group of Institut Fresnel for the modelling and the metrology of light scattered by complex optical components for space applications. A specific care will be given to recent studies performed on narrow band filters for earth observation and high performances mirrors. For each of these applications, the specific problematics and corresponding challenges will be presented and experimental and numerical results will be detailed. The agreement between metrology and modelling will be highlighted.