Whispering-gallery-mode (WGM) microresonators provide a highly efficient platform for studying nonlinear optical phenomena and light–matter interactions, owing to their ability to confine light with ultra-low loss and high quality (Q) factors. This dissertation introduces a novel method for visualizing intra-cavity dynamics by collecting scattered light from the microresonator using a short-wave infrared (SWIR) camera. This approach enables direct observation of spatial mode evolution associated with nonlinear effects such as spontaneous symmetry breaking (SSB), Kerr comb generation, and symmetry breaking. Unlike conventional spectral measurements, the visualization technique offers spatially resolved insight into intra-cavity processes, opening new possibilities for near-field sensing, defect detection, and photonic switching. On the fabrication side, we develop a simplified, metal-mask-free method for constructing high-Q aluminum nitride (AlN) microresonators using a single silicon nitride hard mask and a conductive polymer. This method achieves intrinsic Q factors up to one million and enables strong nonlinear responses, including third-harmonic generation, Raman lasing, and broadband Kerr frequency combs. The integration of spatial imaging with nonlinear photonics paves the way for high-resolution device diagnostics, precision sensing, and next-generation on-chip photonic platforms.
Haochen Yan (Thu,) studied this question.