Mode‐dependent Far‐field Radiation of Circularly Polarized Light by a Single Plasmonic Nanohelix

Abstract Chiral plasmonic nanoantennas exhibit unique chiroptical properties in both the near‐field and far‐field, offering exciting opportunities for applications in chiroptical sensing, circularly polarized luminescence, and quantum communication. Recent advances in chiral plasmonics have facilitated the creation of nanoparticles with intrinsic chirality at the single‐particle level. However, the far‐field directionality of these chiral nanoantennas is not well understood. In this work, A numerical study is conducted on a single plasmonic nanoantenna that undergoes a size‐preserving compression, transitioning from a straight nanorod to left‐ or right‐handed helices with varying pitches. These nanostructures showcase distinct mode‐dependent chiroptical far‐field properties, encompassing positive or negative dissymmetry factors, 3D power radiation patterns, and angular distribution of circular polarization, under both plane‐wave and point‐source excitations. The findings provide new insights into angle‐resolved spectroscopies of intrinsically chiral plasmonic nanoparticles and the applications of chiral plasmonic nanoantennas for controlling circularly polarized light emission in nanophotonics.