Anomalous light scattering from multilayer coatings with nodular defects

Optical coatings with extremely low scattering losses are critical in high-precision optical systems. In this study, the abnormal scattering of nodular defects in high-reflection multilayer coatings was investigated experimentally and theoretically. The measurements and finite-difference time-domain simulations showed that the total scattering does not vary monotonically with increasing nodular structure size, but rather oscillates. Field distribution analysis revealed that the anomalous scattering originates from the coupling of the incident light with the surface wave at the top of the defects. These findings contribute to the field of low-scattering-loss multilayer coatings and high-precision optical systems.