New challenges in optical coating design

Modern mathematical algorithms allow to theoretically generate thin film designs that fit nearly any reasonable specification. Nevertheless, as practice has shown, the gap between calculated and technologically achievable characteristics may be significant, so that the search for qualitatively new design and production tools is still in progress and represents one of the most complex challenges in thin optical coating theory and technology today. Such new design challenges include the incorporation of gradient index layers into classical designs, the design of rugate filters, or novel filter concepts that are based on resonant grating waveguide structures. Moreover, the development of novel composite coating materials is expected to facilitate the optimisation of future designs.