OPTIMIZATION OF INTERFERENCE FILTERS WITH GENETIC ALGORITHMS APPLIED TO SILVER-BASED HEAT MIRRORS

In the optimization of multilayer stacks for various optical filtering purposes not only the thicknesses of the thin films are to be optimiz ed, but also the sequence of materials. Materials with very different optical properties, such as metals and dielectrics, maybe combined. A genetic algorithm is introduced to search for the optimal sequence of materials along with their optical thicknesses. This procedure is appl ied to a heat mirror in combination with a blackbody absorber for ther mal solar energy applications at elevated temperatures (250-degrees-C) . The heat mirror is based on silver films with antireflective dielect ric layers. Seven dielectrics have been considered. For a five-layer s tack the sequence (TiO2/Ag/TiO2/Ag/Y2O3) is found to be optimal.