Optical dispersion and band gap of Silicon-SiO₂ quantizing nanolaminates

Quantizing nanolaminates are under development for use as materials with optimized properties for optical interference coatings. The optical dispersion needs a different description compared with simply mixing the basic materials because of the band gap shift. Although quantizing nanolaminates consist of alternating high- and low-index materials, representing them as a conventional layer stack can be questionable due to their extremely thin-often nanometer-scale-layers. This work gives an overview of Si-SiO₂ layer stacks over a large range of different thickness combinations. The samples range from an almost pure SiO₂ single layer to an almost standard interference stack of both materials. By treating all samples as single layers and fitting their dispersions to an arbitrary function, we examined which combinations show a shift in the absorption edge and can be described with sufficient accuracy that they are suitable for production.