Broadband antireflective coating for NEOSTED

Abstract

This paper deals with the development of a broadband antireflective coating for a special optical components for the NEOSTED project by European Space Agency (ESA). The aim of this work was to find a suitable design of the optical coating and to develop its production process so it meets the main requirement in which the average reflectance of the coating must be under 0.5 % for wavelengths in the range of 470 - 770 nm. The combination of titanium dioxide (TiO2) and silicon dioxide (SiO2) prepared by the ion beam assisted deposition (IBAD) was chosen for practical experiments and finally for the production as well. The final decision among the proposed designs and materials involved especially the number of layers used in the design in combination with the thickness control technology. From preproduction tests it turned out that the quartz monitor with the thickness set point correction based on a post process measurement is suitable for controlling deposited thickness in the application. This paper presents data from the preproduction tests and data from the first part of the production. A homogeneity of the deposited layer thickness was evaluated based on the measurement of the thickness across the sample.