Anapole states and transverse displacement sensing based on the interaction between cylindrical vector beams and Au core-Si shell nanodisks

Abstract

Precise optical control at the nanoscale is crucial for advancing photonic devices and sensing technologies. Herein, we theoretically introduce what we believe to be a novel approach for nano-optical manipulation, employing Au core-Si shell nanodisks interacting with tightly focused cylindrical vector beams to achieve electric and magnetic anapole states. Our investigations unveil that the interplay between individual nanodisks and radially polarized beams (RPBs) located in the center of RPBs yields a position-dependent electric anapole state. Conversely, under illumination by azimuthally polarized beams (APBs), the electric anapole state exhibits independence from the nanodisk's positioning and is accompanied by significant magnetic dipole excitations. Furthermore, the interaction between APBs and nanodisk multimers enables the formation of a magnetic anapole state, marking an advancement in nano-optical control. This study further explores the application of the position-dependent electric anapole state for nanoscale transverse displacement sensing, which allows for precise determination of the nanodisk's position within a plane. These findings not only facilitate versatile control over anapole states but also set a foundation for integrated displacement sensing technologies on-chip.