Custom-Built Vision-Assisted Arc Discharge System for Fabricating High-Q In-Line Microbubble Resonator Arrays.

Whispering gallery mode microbubble resonators (MBRs) are prominent optofluidic platforms, yet fabricating highly symmetric in-line arrays remains a technical challenge. Here, we demonstrate a custom-built, vision-assisted arc discharge apparatus for the deterministic fabrication of high-Q MBRs. Using finite-element simulations and microscopic observations, we reveal that asymmetric expansion is primarily driven by transverse misalignment within the plasma arc and intrinsic thermal anisotropy caused by the current crowding effect. Guided by these physical insights, we utilize real-time three-axis spatial compensation to successfully fabricate highly symmetric, cascaded in-line MBR arrays on a single continuous capillary. Optical characterization of a 16-cavity array demonstrates excellent performance reproducibility, with 12 individual microbubbles achieving ultra-high Q-factors exceeding 107. This highly controllable approach provides a robust platform for distributed microfluidic sensing and integrated lab-on-a-chip applications.