A comparative study of dry-etching nanophotonic devices on a LiNbO3-on-insulator material platform

Three different novel dry-etching methods have been employed to fabricate nanophotonic devices upon a thin-film lithium niobate on insulator material platform. Different dry-etching processes and their advantages, drawbacks and applicable scenarios are systematically studied. Ultra-smooth etching surface with roughness of 0.46 nm (Rq), low-loss ridge waveguides with extracted propagation loss of 1.42 dB/cm, and microring resonators with high optical quality factors up to 1.4×10⁵ are demonstrated using the optimized low-loss etching recipe. The low-loss etching technique lays a foundation for monolithic integration of passive optical components with quantum dots, on-chip broadband electro- optic modulators and wafer-scale lithium niobate integrated photonic circuits.