Fabrication of High-Quality Whispering Gallery Mode Microbubble Resonators

We demonstrate a robust and standardized method for the fabrication of high-quality factor (Q-factor) Whispering Gallery Mode (WGM) Microbubble resonators (MBRs) with a precision glass processing machine (PGP). Microbubble resonators are a unique class of WGM devices with integrated fluidic channels, making them ideal for diverse sensing applications. Herein, we show a standardized protocol to fabricate high-Q microbubble resonators through the optimization of key performance metrics, such as Q-factor and wall thickness. We also show methods to improve the sensitivity of the platform to refractive index changes and other sensing targets through Hydrofluoric acid (HF) wet etching. Lastly, a brief analysis of the resistance of microbubbles to fluid flow is discussed, showing that smaller-diameter microbubbles exhibit greater resistance to flow for analyte delivery-a factor that should be considered for analyte delivery. The implementation of this refined fabrication protocol not only increases the success rate of device production but also reduces fabrication time. Moreover, the protocol can be expanded to other techniques used to produce MBRs, such as CO₂ laser-based methods.