Optical multilayer coating synthesis by simultaneous optimization of number of layers, refractive index, and thickness

Abstract

Multilayer coatings are widely used in various optical parts, for example, multimode optical fibers, beam splitters, and antireflection coatings. Therefore, the applied range on the specifications of filtering wavelength and the functions of coatings are also various. Conditions of the evaporation process for coatings must be considered; therefore, the total design process requires a special technique. The main difficulty is that the formulation of the multilayer structure to achieve the specified spectral reflectance is usually impossible. To solve the problem generally, the developed design system uses a combinatorial optimization method in the design process. This chapter outlines the optimum design method and lists its essential features. The chapter also illustrates the results for some design examples. In a design of optical multilayer coatings, the determination of the refractive index and thickness of each layer must be in accordance with the specifications on a spectral reflectance. An optimum design system for optical multilayer coatings is developed in this chapter. In the developed system, a spectral reflectance is given as a design specification, and the number of layers, material, and thickness for each layer can be determined under various constraints on the production process and the other conditions. Materials of the layers are selected from the database prepared by the manufacturer in advance.