Mirror Surface Nanostructuring via Laser Direct Writing—Characterization and Physical Origins

Abstract

AbstractThe addition of an optically absorptive layer to otherwise standard dielectric mirrors enables a set of laser direct writing nanostructuring methods that can add functionality to such mirrors while retaining their high reflectivity. A thorough characterization of this method is given in this paper, and its physical origins are investigated. In particular, these measurements show that laser direct writing of such mirrors has a reversible and a permanent component. The reversible process originates from the thermal expansion of the surface and allows a simple yet precise way to temporarily modify the shape of the mirror. Scanning electron microscope cross‐sectional images suggest that the permanent part of the nanostructuring process is due to thermally induced pore formation and enlargement in the tantalum oxide layers of the used dielectric mirror.