Optimizing flatness

Stress in thin films may cause a slightly deformed surface, concave if the stress is tensile, convex if it is compressive. The easiest way to avoid deformation is to use thicker substrates but often this is not possible.

LASEROPTIK has approved coating processes in place that help to reduce stress in the coating and to avoid unwanted (a)spherical effects for substrates with extraordinary flatness requirements.

Additionally, the stress can be reduced significantly by optimizing the coating design. Taking the Stoney equation into account, the number and thickness of the layers can be adapted to the size and elastic properties of the substrate. But this may lead to a higher total film thickness and reduced spectral performance. For optimizing coating processes LASEROPTIK has a dedicated machine with an optional in-situ stress measurement.