Observation of Wide Bandwidth and Giant Chiroptical Response Empowered by Core–Shell Micro-Helixes

Abstract

Helical microstructures exhibit unprecedented chiroptical responses particularly interesting for emerging applications such as broadband photonic components. To explore their chiral behaviors, the micro-helixes composed of polymer cores and platinum shells are proposed and realized via a two-step process combining two-photon polymerizations and sputter coating. Thanks to the core–shell multi-material configurations, the micro-helixes packed in a dense array generate an ideal chiral lineshape. Overspanning a wide range from 3 to 7 μm, the reflection-based g factors approach the upper amplitude limits. Numerical modeling reveals that polarization-induced spectra result from overlapping modes similar to the previously reported solid metal helixes. The further chiral spectrum comparisons confirm that the core–shell spirals exhibit a 25% bandwidth increase compared to solid platinum helixes of same sizes. Interestingly, the asymmetrically distributed platinum shell may further expand the operational band. Overall, comprehensive studies are performed on multi-material micro-helixes, which could provide additional flexibility to tailor their chiroptical properties, enabling the production of high-performance chiral microstructures for diverse applications.