Wavefront control in the design of narrow-and broad-band optical coatings

Abstract

The wavefront distortion induced by some optical coatings has often been underestimated with serious consequences in the performance of optical instruments. The typical approach to face such inconvenience consists in modifying the shape of the coated optics by compensating either the bending induced by stress or the geometrical thickness variations in nonuniform coatings. A relevant contribution to the wavefront distortion can also be given by the interference in the coating layers and a standard approach to overcome such problem is not available. In this work the wavefront deformation that is due to the spatial non-uniformity of thin-film optical coatings is analyzed, with the aim of identifying simple structures in which the influence of thickness non-uniformity on the wavefront shape is minimized. Some examples are reported especially for high-reflectance coatings.