Magnetic Field Enhanced Optical Chirality of Plasmonic Ring-disk Nanostructure

Optical chirality or chiral nearfields are of vital significance in diversity of applications. Natural chiral nearfields are too weak to be detected. Moreover, existence of opposite chiral nearfields under left circularly polarized (LCP) and right circularly polarized (RCP) light irradiations is necessary for better efficacy in practical applications. Herein, a novel idea based on magneto-optical Kerr effect (MOKE) is proposed for enhancing chiral nearfields of concentric ring-disk (RD) plasmonic nanostructure. Theoretical results show more than 100% increment in chiral nearfield enhancement in presence of magnetic field as compared to that without magnetic field. This is attributed to localized surface plasmon coupling mediated by magnetic field. Chiral nearfields are found being dependent on structural parameters. Magnetic field direction reversal/change strongly influenced enhancement in chiral nearfields. Our results provide promising way for enhancing chiral nearfields and producing opposite chiral nearfields with magnetic field introduction which can ultimately enhance practical applications of chiral nearfields.