Structural Color from Multi-bounce Reflection Interference in Metalized Microstructures

The development of materials and methods for controlling iridescent structural color arising from optical interference has attracted considerable attention for a variety of applications ranging from anticounterfeiting to displays. Here, we investigate structural color generated by multibounce reflection interference within metallized microstructures. The multi-bounce reflection interference mechanism, which was recently reported, has previously only been studied within materials where reflectivity originates from total internal reflections on a concave interface. By instead inducing reflectivity with metallization, the interference conditions are altered and different optical properties arise. Using angularly resolved far-field optical analysis and ray tracing simulations, the differences between metal-induced multibounce reflection interference and total internal reflection-induced interference are described. The incorporation of metallized optical interfaces beneficially increases microstructure reflectivity, removes the restrictions on material refractive index, and further enables the use of diverse microstructure geometries combining both concave and convex curvatures. These results provide insight into how metallization can be harnessed for designing optical interference within microstructures with improved structural color saturation and reflectivity.