Observation of an exceptional point in a chaotic optical microcavity

TL;DR

This paper reports the spectroscopic observation of an exceptional point in a chaotic optical microcavity, revealing a transition between crossing modes and a singular topology affecting mode labeling.

Contribution

It provides the first experimental observation of an exceptional point in a chaotic microcavity, highlighting the effects of deformation and openness on mode interactions.

Findings

Observation of an exceptional point in a chaotic microcavity

Transition from diabatic crossing to avoided crossing

Singular topology causes mode labeling inconsistency

Abstract

We present spectroscopic observation of an exceptional point or the transition point between diabatic crossing and avoided crossing of neighboring quasi-eigenmodes in a chaotic optical microcavity with a large size parameter. The transition to the avoided crossing was impeded until the degree of deformation exceeded a threshold deformation owing to the system's openness also enhanced by the shape deformation. As a result, a singular topology was observed around the exceptional point on the eigenfrequency surfaces, resulting in fundamental inconsistency in mode labeling.