Scatter losses of broadband interference coatings

Abstract

The scattering behavior of dielectric broadband coatings was measured in the 0.4–1.0-μm wavelength range. It is shown that the scattering properties are determined entirely by the surface roughness and the optical properties of the films. Scatter losses of ZnS, ThF₄, and MgF₂ monolayers are around 10⁻²%, but broadband mirrors may have losses of more than 10% due to resonant conditions within the multilayer structure. To calculate the scattering behavior of any multilayer system and to reduce the losses of broadband coatings, we developed a scattering model. The calculations are in good agreement with experimental results.