Batch-processed high-Q integrated lithium-niobate-on-insulator ridge waveguide whispering-gallery resonators

Lithium niobate whispering-gallery resonators (WGRs) show high intensity enhancement due to small mode volumes and high Q-factors. With bulk WGRs, shaped by diamond-blade-cutting tools followed by surface polishing, Q-factors in the range of 1011 have been demonstrated, which make them of significant interest for e.g. nonlinear-optical frequency conversion [1]. However, WGRs are still rare in commercial products due to the serial and thus expensive fabrication. Thus integration of WGRs on chip level became of great interest in the past years.