A high-Q, ultrathin-walled microbubble resonator for aerostatic pressure sensing

TL;DR

This paper demonstrates a microbubble whispering gallery resonator with ultrathin walls and high Q-factor for highly sensitive aerostatic pressure sensing, achieving resolutions below 0.2 mbar.

Contribution

It introduces a novel microbubble resonator with 500 nm wall thickness and high Q-factor, enhancing pressure sensitivity and resolution in optical sensing.

Findings

Sensitivity of 19 GHz/bar at 1.55 μm

Improved sensitivity of 38 GHz/bar at 780 nm

Pressure resolution of 0.17 mbar with Q > 5×10^7

Abstract

Sensors based on whispering gallery resonators have minute footprints and can push achievable sensitivities and resolutions to their limits. Here, we use a microbubble resonator, with a wall thickness of 500 nm and an intrinsic Q-factor of $10^7$ in the telecommunications C-band, to investigate aerostatic pressure sensing via stress and strain of the material. The microbubble is made using two counter-propagating CO$_2$ laser beams focused onto a microcapillary. The measured sensitivity is 19 GHz/bar at 1.55 $\mu$m. We show that this can be further improved to 38 GHz/bar when tested at the 780 nm wavelength range. In this case, the resolution for pressure sensing can reach 0.17 mbar with a Q-factor higher than $5\times10^7$.