Extinction of guided light induced by coupled spiral meta-atom resonators at arbitrary order exceptional points

Abstract

Exceptional points (EPs) in non-Hermitian systems can give rise to intriguing effects not available in conventional Hermitian systems due to their unusual properties. Using full-wave simulations, we investigate the scattering, absorption, and transmission of guided light at arbitrary order exceptional points in a non-Hermitian system consisting of coupled spiral meta-atom resonators sitting on a dielectric waveguide. The EPs are realized by exploiting the unidirectional coupling of the chiral dipole modes in the subwavelength meta-atom resonators. The scattering and absorption of the resonators induce the attenuation of the guided light in the dielectric waveguide. We show that the EPs can give rise to a plateau in the attenuation spectrum of the guided light with near-zero transmission, i.e., the guided light is almost completely dissipated via the resonators in the forms of intrinsic material loss and radiation loss. In addition, the width of this plateau (i.e., the extinction bandwidth) increases with the order of the EP. The phenomena can be understood by employing a coupled mode analysis, with the analytical results quantitatively agree with the numerical results. The results may find applications in designing novel on-chip optical absorbers and sensors.