MAXIMUM REFLECTANCE OF MULTILAYER DIELECTRIC MIRRORS IN THE PRESENCE OF SLIGHT ABSORPTION

A new design technique for multilayer reflectors is described. It is useful when slight absorption by one or both of the coating materials limits the performance of the reflector. The basic procedure is to add layers to a given substrate or multilayer system one pair at a time. The thickness of each layer is chosen to give the maximum increase in reflectance for each pair of layers added. By using such optimized pairs, it is possible to exceed the reflectance limit usually imposed on quarter-wave stack reflectors by absorption. Expressions for the optimum design and the ultimate reflectance for a high reflector made with a given set of coating materials are provided. 9 refs.