An Ultra-High-Q Lithium Niobate Microresonator Integrated with a Silicon Nitride Waveguide in the Vertical Configuration for Evanescent Light Coupling

We demonstrate the hybrid integration of a lithium niobate microring resonator with silicon nitride waveguide in vertical configuration to achieve efficient light coupling. The is fabricated on insulator (LNOI) substrate using photolithography assisted chemo-mechanical etching (PLACE). A fused silica cladding layer deposited LNOI ring resonator. further produced by first fabricating trench while focused ion beam (FIB) for facilitating evanescent coupling, followed formation bottom trench. FIB ensures required high positioning accuracy between and Q-factors as 1.4 × 107 vertically integrated device.