Reflectivity improvement of lightweight active cooled metal mirrors manufactured by additive manufacturing

In recent years, additive manufacturing (AM) has appeared as a revolutionary approach in designing and fabricating active-cooled mirrors (ACMs). In particular, selective laser melting (SLM) allows more design freedom (with high resolution) while reducing weight and material costs compared to conventional manufacturing methods. In the current research, SLM using a Ytterbium fiber laser (200 W, 1030 nm) and a high-speed scanner for precise active cooled mirror base manufacturing was used. Nevertheless, without a proper surface finish, the metal surface has relatively low reflectance. This limits the use of element for laser and space-based applications. In the present research, we show how HR silver-aluminum (Ag–Al) mixed coating deposited using magnetron sputtering may help. The final element reflectance was increased up to >95 % in the vis-IR range and the arithmetic average roughness was less than 3–5 nm. Optical performance and surface quality were evaluated in each manufacturing step. Fabricated coatings' properties are compared with those used in earlier space missions to assess their main parameters. Additive manufacturing approach successfully enabled the integration of complex internal cooling channels that cannot be achieved through conventional machining methods, providing a foundation for enhanced thermal management in high-power optical applications.