On-chip three-dimensional high-Q microcavities fabricated by femtosecond laser direct writing

TL;DR

This paper demonstrates the fabrication of 3D high-Q microcavities on a chip using femtosecond laser direct writing, achieving high quality factors and versatile positioning, with potential improvements through better motion stage resolution.

Contribution

It introduces a novel method for creating 3D high-Q microcavities on-chip using femtosecond laser fabrication combined with chemical etching and laser annealing.

Findings

Microcavities with Q-factor up to 1.07x10^6 achieved.

Flexible tilting and positioning of microcavities demonstrated.

Surface smoothness improved via CO2 laser annealing.

Abstract

We report on the fabrication of three-dimensional (3D) high-Q whispering gallery microcavities on a fused silica chip by femtosecond laser microfabriction, enabled by the 3D nature of femtosecond laser direct writing. The processing mainly consists of formation of freestanding microdisks by femtosecond laser direct writing and subsequent wet chemical etching. CO2 laser annealing is followed to smooth the microcavity surface. Microcavities with arbitrary tilting angle, lateral and vertical positioning are demonstrated, and the quality (Q)-factor of a typical microcavity is measured to be up to 1.07x10^6, which is currently limited by the low spatial resolution of motion stage used during the laser patterning and can be improved with motion stages of higher resolutions.