Antireflective coatings for plastic optics with high angular tolerance based on nanostructuring technology AR-plas2

Next generation AR/VR devices require miniaturization, lighter materials, and larger fields of view, leading to the use of advanced optical designs with complex lens geometries made from plastic materials. In addition, extremely high angles of light incidence can occur in pupil expanders or waveguide combiners. Antireflective solutions called AR-plas2 nanostructures were developed at Fraunhofer IOF to address extreme specifications in terms of spectral and angular bandwidth. The technology is based on a plasma etching process with an Ar/O2 plasma using the Advanced Plasma Source of a vacuum box coater from Bühler Leybold Optics. Nanostructured silica layers with effective refractive indices down to 1.05 were produced by overcoating plasma-structured organic thin films with silica and subsequent removal of the organic components. By combining these effective media with interference layers, antireflective coatings with a residual reflectance of only 8% up to an AOI of 80° were designed for the visible spectral range on Zeonex substrates. Measurements on experimentally realized designs consisting of several SiO2 nanostructures only show a reflection of less than 3% at an AOI of 70°.