Engineered pseudo and hybrid anapole states in a silicon nanoresonator metasurface

Abstract

Significant attention has been devoted to realizing non-radiating states (popularly known as anapole states) in several systems due to the strong localization of electromagnetic fields, which can be attained through destructive interference of various dipole moments, yielding fundamental or higher-order anapole states. Recently, it has been shown that the interference of higher-order excitation also permits light manipulation at the nanoscale and provides additional benefits such as efficient power transfer and enhancement in nonlinearities. In this work, we report discrete electric anapole (pseudo and hybrid) by careful design of an all-dielectric metasurface consisting of a silicon nanodisk such that a higher-order toroidal electric dipole (TD) and quadrupole interfere destructively, producing a hybrid anapole at 815 nm, whereas the pseudo anapole is generated when TD and second-order TD minima occur at the same wavelength of 522 nm. The phase plots confirm the findings of these radiationless states. Such dual and distinct non-radiating current configurations may find applications in spectroscopy, sensing, switching, optical nonlinearity, and optomechanics.