Unidirectional emission from circular dielectric microresonators with a point scatterer

TL;DR

This paper explores how placing a point scatterer inside a circular dielectric microresonator can produce highly directional emission while maintaining high Q-factors, combining numerical analysis with classical ray optics insights.

Contribution

It introduces a novel approach of using an off-center point scatterer in microresonators to achieve unidirectional emission with high Q-factors, supported by resonance spectrum analysis.

Findings

Certain modes exhibit both high Q-factors and directional emission.

Classical ray optics effectively guides the optimization of system parameters.

Exceptional points significantly affect resonance behavior.

Abstract

Circular microresonators are micron sized dielectric disks embedded in material of lower refractive index. They possess modes of extremely high Q-factors (low lasing thresholds) which makes them ideal candidates for the realization of miniature laser sources. They have, however, the disadvantage of isotropic light emission caused by the rotational symmetry of the system. In order to obtain high directivity of the emission while retaining high Q-factors, we consider a microdisk with a pointlike scatterer placed off-center inside of the disk. We calculate the resulting resonant modes and show that some of them possess both of the desired characteristics. The emission is predominantly in the direction opposite to the scatterer. We show that classical ray optics is a useful guide to optimizing the design parameters of this system. We further find that exceptional points in the resonance spectrum influence how complex resonance wavenumbers change if system parameters are varied.