Directional waveguide coupling from a wavelength-scale deformed microdisk laser

TL;DR

This paper demonstrates a novel method for uni-directional coupling of microdisk laser emission to a waveguide, utilizing waveguide placement and physical effects to control light directionality, confirmed through simulation and experiments.

Contribution

It introduces a wavelength-scale deformed microdisk laser that achieves directional coupling via Goos-Hänchen shift and Fresnel filtering effects, with experimental validation.

Findings

Successful demonstration of uni-directional evanescent coupling

Control of coupling direction by waveguide placement

Reduction of spatial hole burning effect

Abstract

We demonstrate uni-directional evanescent coupling of lasing emission from a wavelength-scale deformed microdisk to a waveguide. This is attributed to the Goos-H\"anchen shift and Fresnel filtering effect that result in a spatial separation of the clockwise (CW) and counter-clockwise (CCW) propagating ray orbits. By placing the waveguide tangentially at different locations to the cavity boundary, we may selectively couple the CW (CCW) wave out, leaving the CCW (CW) wave inside the cavity, which also reduces the spatial hole burning effect. The device geometry is optimized with a full-wave simulation tool, and the lasing behavior and directional coupling are confirmed experimentally.