Coupled nonidentical microdisks: Avoided crossing of energy levels and unidirectional far-field emission

Abstract

We investigate two coupled microdisks with nonidentical radii focusing on the parametric evolution of energy levels and the unidirectional far-field emission. We show that the evolution of energy levels is characterized by the avoided crossing intrinsically associated with the exceptional point or the non-Hermitian degeneracy. These spectral properties explain highly asymmetric near-field intensity pattern of the resonance mode. The observed unidirectional far-field emission is shown to be understood by considering the forbidden interdisk coupling in the ray picture induced by the frustrated total internal reflection near the closest point between two disks when the interdisk distance is small enough.