Three-layer antireflection coatings: a new method for design and optimization

An algorithm offering a simpler and faster optimization procedure is developed for the design of multilayer antireflection coatings, and a closed-loop nonlinear approximation technique is used to arrive at the exact thickness of each layer. The method has been used in the design of systems with high- and low-index substrates normally used in IR regions and in visible to near-IR regions, respectively. In a comparative study with other techniques the present design was preferred over Dobrowolski's (1981, 1982) if a wider spectral bandwidth is of more importance than spectral losses. The use of this method permits optimum design with refinement in only one thickness. This non-lambda/4 system gives higher flexibility in choosing the refractive index of the materials and correcting the system in in-situ conditions.