Optimization of Multilayer Optical Films with a Memetic Algorithm and Mixed Integer Programming

Multilayer optical films have been extensively used in optical technology, but the design of multilayer structures for broadband applications is often challenging due to the need to incorporate material dispersion. Here, we present an implementation of a memetic algorithm based on mixed integer programming, which is especially suited for practical broadband optimization of layered thin-film materials. In our implementation, the optimization variables consist of a list of discrete variables that represents different dielectric materials, along with a list of continuous variables that represents the thicknesses of each material. As a set of concrete demonstrations, we optimize the spectra of a radiative cooling device and an incandescent light bulb filter. The resulting structures from the optimization can, by using more materials, achieve better performance than their counterparts in the literature while using fewer numbers of material layers.