Extreme Sensitivity of Output Directionality to Boundary Perturbation in Wavelength-Scale Microcavities

TL;DR

This paper reveals that tiny shape deformations in wavelength-scale microcavities can cause drastic changes in output directionality, enabling potential high-resolution sensing applications.

Contribution

It uncovers the extreme sensitivity of microcavity emission directionality to boundary perturbations and explains this phenomenon through a novel perturbation theory analysis.

Findings

Small boundary changes flip emission direction by 180 degrees

Shape perturbations cause strong mixing of cavity resonances

Potential for high-resolution detection and sensing

Abstract

We report a surprising observation that the output directionality from wavelength-scale optical microcavities displays extreme sensitivity to deformations of the cavity shape. A variation of the cavity boundary on the order of ten thousandth of a wavelength may flip the output directions by 180 degrees. Our analysis based on a perturbation theory reveals that a tiny shape variation can cause a strong mixing of nearly degenerate cavity resonances with different angular momenta, and their interference determines the farfield emission pattern. This work shows the possibility of utilizing carefully-designed wavelength-scale microcavities for high-resolution detection and sensing applications.