Observation of mode-mixing in the eigenmodes of an optical microcavity

TL;DR

This paper introduces a novel method to measure the complex coupling parameter of coupled modes in an optical microcavity by directly analyzing eigenmodes, revealing primarily conservative mode-mixing at the mirror surface.

Contribution

A new measurement technique for the complex coupling parameter based on eigenmode analysis, applicable to various coupled systems.

Findings

Mode-mixing observed at the mirror surface in an optical microcavity.

Coupling is predominantly conservative, as confirmed by measurements.

Method allows accurate determination of mode coupling without frequency shift measurements.

Abstract

We present a method to determine the complex coupling parameter of a two-coupled-modes system by directly measuring the coupled eigenmodes rather than their eigenvalues. This method is useful because mode-mixing can be observed even if frequency shifts can not be measured. It also allows to determine the complex coupling parameter, from which we conclude that the observed coupling is mainly conservative. We observe mode-mixing in an optical microcavity, where the modes couple primarily at the mirror surface, as confirmed by AFM measurements. The presented method is general and can be applied to other systems to measure mode coupling more accurately and to determine the nature of the coupling.