Vertically Stacked Split-Ring Resonators Derived from Block Copolymer Self-Assembly for Polarization-Sensitive Dichroic Responses

We realized stacked split-ring resonators (SSRRs) arrays from “pagoda-like” nanorods over a large area (~cm²) exhibiting polarization differences in visible and near-infrared (NIR) wavelengths. The lamellar-forming polystyrene-block-poly (methyl methacrylate) copolymer (PS-<i>b</i>-PMMA) was confined in cylindrical pores of aluminum oxide (AAO) template grafted by thin neutral brush layers to create this array of "pagoda-like" nanorods. Along the nanorod direction, PS and PMMA lamellae nanodomains with 25 nm were alternately stacked. After the AAO template was removed, “pagoda-like” nanorods were generated by O₂ reactive ion etching. Silver SSRRs formed from the “pagoda-like” nanorods via oblique angle deposition (OAD) exhibit optical polarization differences due to asymmetric architectures. This method of constructing complex nanoscale architectures using block copolymer self-assembly and tilt deposited plasmonic metal could be applied to optical anti-counterfeiting, structural color, and commercial optical components in a large area.