Designing with very thin optical films

There is increasing interest in the design of films with thicknesses on the order of 10 nm and less for a variety of applications, such as nanoparticles, plasmonics, quantum dots, solar reflectors, black mirrors, etc. The indices of refraction (n and k) for the effective media of such coatings depend on the materials with which such "layers" interface and the specific process parameters used to produce those films. The structures may typically be nucleating island structures and may also be continuous films. A key factor is that the n and k values vary in thickness until some thickness is obtained, usually >20nm. Heretofore, to the best of our knowledge, films have not taken into account thickness index variations during the design process. Software has now been developed where the index at a given thickness is computed at each iteration of the design optimization process. This allows more realistic design results utilizing the full representation of the behavior of the layers in question; the resulting coatings, when produced, are in better agreement with the designs. Including n and k versus wavelength and thickness in the design process is here referred to as double dispersion.