Coupled non-identical microdisks: avoided crossing of energy levels and unidirectional far-field emission

TL;DR

This paper studies coupled non-identical microdisks, revealing how avoided energy level crossings relate to unidirectional emission, with insights into spectral properties and far-field emission patterns.

Contribution

It demonstrates the connection between avoided crossings and unidirectional emission in coupled microdisks, highlighting the role of non-Hermitian degeneracies and ray picture analysis.

Findings

Energy levels exhibit avoided crossing linked to exceptional points.

Unidirectional far-field emission explained by forbidden inter-disk coupling.

Spectral properties account for asymmetric near-field patterns.

Abstract

We investigate two coupled microdisks with non-identical 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 inter-disk coupling in the ray picture induced by the frustrated total internal reflection near the closest point between two disks when the inter-disk distance is small enough.