Multimode Coupling by Boundary Wave Scattering

TL;DR

This paper demonstrates how boundary wave scattering can be used to control multimode coupling in optical microcavities, affecting the cavity's external field distribution.

Contribution

It introduces a method to control multimode coupling via boundary wave scattering in optical microcavities, supported by a perturbation theory analysis.

Findings

Coupling among multiple resonances can be controlled by boundary wave scattering.

Different scattering paths can enhance or reduce mode coupling.

Controlled coupling significantly alters the external cavity field distribution.

Abstract

We show that coupling among multiple resonances can be conveniently introduced and controlled by boundary wave scattering. We demonstrate this principle in optical microcavities of quasi-circular shape, where the couplings of multiple modes are determined by the scattering from different harmonic boundary deformations. We analyze these couplings using a perturbation theory, which gives an intuitive understanding of the first-order and higher-order scattering processes. Different scattering paths between two boundary waves can either enhance or reduce their coupling strength. The effect of controlled multimode coupling is most pronounced in the direction of output from an open cavity, which can cause a dramatic change of the external cavity field distribution.