Super FSR tunable optical microbubble resonator

TL;DR

This paper introduces the first mechanically fully tunable silica microbubble optical resonator with a tunable bandwidth exceeding its azimuthal free spectral range, enabling broader spectral control.

Contribution

It presents the design and demonstration of a novel, fully mechanically tunable microbubble resonator with a large tunable bandwidth surpassing the free spectral range.

Findings

Tunable bandwidth is more than twice the azimuthal free spectral range.

Microbubble resonator achieves full mechanical tunability.

Resonator has a 100 micron radius and micron-scale wall thickness.

Abstract

An optical resonator is often called fully tunable if its tunable range exceeds the spectral interval that contains the resonances at all the characteristic modes of this resonator. For the high Q-factor spheroidal and toroidal microresonators, this interval coincides with the azimuthal free spectral range. In this Letter, we demonstrate the first mechanically fully tunable spheroidal microresonator created of a silica microbubble having a 100 micron order radius and a micron order wall thickness. The tunable bandwidth of this resonator is more than two times greater than its azimuthal free spectral range.