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

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.