Simulation of Tailoring Chiral Light Propagation in Gold–Silver Hybrid Plasmonic Waveguides

Nanoplasmonic waveguides can efficiently manipulate the propagation characteristics of chiral light and hold great promise for integrated nano optics and on-chip optical information processing. Previous studies have demonstrated that gap plasmon structures composed of gold nanorod and silver nanowire can break the propagation symmetry of chiral light, thereby enabling asymmetric directional propagation. However, there remains considerable scope for enhancing the directional selectivity of these structures. In this work, we systematically investigate the mechanism of how the geometrical parameters of nanostructures regulate the directional propagation of chiral light. Based on the finite-difference time-domain method, the propagation behavior and evolution of directionality of chiral light in nanoplasmonic waveguides are analyzed in detail by changing the morphology and length of gold nanorods. The results show that the geometrically optimized nanostructures can significantly enhance the stability of directional chiral light propagation. At the same light-source position, the directionality of the gold nanorod with tips is approximately 56%, whereas that of the gold nanorod without tips remains approximately 89%. Further investigations show that structural modification of the silver nanowire or geometrical optimization of the structure can effectively reshape the local electromagnetic field distribution, enabling precise control over the propagation direction of chiral light. This work elucidates the physical mechanism underlying geometry-controlled chiral plasmonic propagation and provides a new design strategy for the structural design and performance optimization of high-performance chiral nanophotonic devices, with promising potential applications in chiral optical recognition, on-chip optical information processing, and nanoscale optical communication.