Whispering-gallery mode micro-kylix resonators

TL;DR

This paper introduces micro-kylix resonators, a new class of micro-resonators that use engineered stress to tune Q-bands efficiently, achieving high Q-factors with minimal size changes, advancing photonics and resonator physics.

Contribution

The paper presents a novel micro-kylix resonator design that enables effective Q-band tuning through stress engineering, reducing size modifications needed for high Q-factors.

Findings

Achieved 60nm Q-band shift with minimal size change

Micro-kylix resonators exhibit higher Q-factors than flat disks

Stress engineering enables precise control of resonator properties

Abstract

Owing to their ability to confine electromagnetic energy in ultrasmall dielectric volumes, micro-disk, ring and toroid resonators hold interest for both specific applications and fundamental investigations. Generally, contributions from various loss channels within these devices lead to limited spectral windows (Q-bands) where highest mode Q-factors manifest. Here we describe a strategy for tuning Q-bands using a new class of micro-resonators, named micro-kylix resonators, in which engineered stress within an initially flat disk results in either concave or convex devices. To shift the Q-band by 60nm towards short wavelengths in flat micro-disks a 50% diameter reduction is required, which causes severe radiative losses suppressing Q's. With a micro-kylix, we achieve similar tuning and even higher Q's by two orders of magnitude smaller diameter modification (0.4%). The phenomenon relies on geometry-induced smart interplay between modified dispersions of material absorption and radiative loss-related Q-factors. Micro-kylix devices can provide new functionalities and novel technological solutions for photonics and micro-resonator physics.