On‐Chip Plasmonic Helical Dichroism

Abstract Chiral systems interacting with optical vortices have been exploited for their exotic chiroptical responses, especially the helical dichroism, which has been proposed for advancing novel photonic devices and developing high‐performance sensing techniques. However, the manipulation of such an intriguing effect has been restricted to free space, hindering its integration into on‐chip photonic systems. Here, to the knowledge, the first demonstration of chip‐scale helical dichroism for surface plasmon polariton optical vortices is presented, enabled by asymmetry scattering of the designed planar chiral system. The plasmonic helical dichroism exhibits 165% and 100% for numerical calculation and experimental demonstration, respectively, significantly surpassing previous studies. Extending helical dichroism into on‐chip plasmonic holds considerable promise for efficient chiroptical detection of planar chiral nanostructures and paves the way for developing chiral optics in integrated photonic technologies.