Thomas Melzig

Optical interference coatings are often applied on both sides of a substrate. We show a concept for an adaptation of broadband monitoring of layer thickness for coating machines that allow simultaneous stack deposition. The underlying algorithm can be used to calculate the optical response of a single substrate with coating stacks on both sides, as well as two substrates mounted on top of each other with a coating stack on one side each. © 2025 Optica Publishing Group.

A-${\rm Si}/{{\rm SiO}_2}$ nanolaminates are deposited by magnetron sputtering and show a decreasing absorption when the a-Si single-layer thickness is reduced from $2.4\;{\rm nm}$ to $0.7\;{\rm nm}$. Moreover, an increase of the Tauc band gap by $0.18\;{\rm eV}$ is measured. Experimental Tauc band gaps are compared to calculated effective band gaps, utilizing a numerical Schrödinger solver.

Abstract During optical monitoring using broadband transmittance measurement, the accuracy depends on how both the substrate and the optical path are aligned. We present a correction procedure to improve the accuracy of the monitoring, even if the substrate has features such as absorption or if there is misalignment of the optical path. The substrate in this case can either be a test glass or a product.