Imperfect chirality at exceptional points in optical whispering-gallery microcavities

Abstract

Non-Hermitian systems have attracted considerable attention for their broad impacts on various physical platforms and peculiar applications. In non-Hermitian systems, both eigenvalues and eigenstates simultaneously coalesce at exceptional points (EPs). As one of the remarkable features of EPs, the field chirality is commonly considered perfect, which is utilized as an intriguing feature to control wave propagation and regarded as a criterion of EP. However, in this work, we discover an imperfect chirality of eigenmodes at the EPs in an optical whispering gallery mode (WGM) microcavity perturbed by two strong nanoscatterers. This counterintuitive phenomenon originates from a strong frequency-dependence of the scattering between the counterpropagating waves at an "effective scatterer", which could be explained by a first-principle-based model considering a dynamic multiple-scattering process of the azimuthally propagating modes. We find that the generally imperfect chirality at the EP tends to be globally perfect with the decrease of the scattering effect induced by the nanoscatterers. Furthermore, the chirality also becomes locally perfect with the decrease of the relative azimuthal angle between the two strong nanoscatterers. This work provides a new understanding of the general properties of chirality at EPs. It will benefit the potential applications enabled by the chirality features of non-Hermitian systems at EPs.

References in corpus (16)

• The physics of exceptional points
• Dynamically encircling exceptional points in a waveguide: asymmetric mode switching from the breakdown of adiabaticity
• Topological energy transfer in an optomechanical system with exceptional points
• Light interaction with photonic and plasmonic resonances
• Observation of coherent perfect absorption at an exceptional point
• Electromagnetically induced transparency at a chiral exceptional point
• The Chirality of Exceptional Points
• Observation of a Chiral State in a Microwave Cavity
• Perfectly absorbing exceptional points and chiral absorbers
• Dynamically encircling exceptional points: in situ control of encircling loops and the role of the starting point
• Exceptional Points in Atomic Spectra
• Chiral Coherent Perfect Absorption on Exceptional Surfaces
• Nonorthogonal pairs of copropagating optical modes in deformed microdisk cavities
• Chiral modes at exceptional points in exciton-polariton quantum fluids
• Quasinormal modes and Purcell factors of coupled loss-gain resonators and index-modulated ring resonators near exceptional points
• Induced transparency: interference or polarization?

Cited by in corpus (3)

• The infinity-loop microresonator: A new integrated photonic structure working on an exceptional surface
• Non-orthogonal cavity modes near exceptional points in the far field
• Local perfect chirality at reflection-zeros away from exceptional points in optical whispering gallery microcavity