Efficient Dual-Polarized Electro-Optically Tunable Microresonators by Utilization of Ultra-Thin Transparent Electrode

High-efficiency electro-optic tuning of microresonators both for TE and TM polarizations is important for versatile advanced photonic applications. This work demonstrates a new device design to realize on-chip lithium niobate microresonators with excellent dual-polarized electro-optic tuning efficiency. The electrode structure is designed such that the produced axial electric field (E _z ) has an obviously stronger intensity distribution in the guided-wave area of microdisk compared to the radial electric field (E _r ). Thus the large electro-optic coefficient r ₁₃ and r ₃₃ can be effectively utilized for the TE- and TM-polarized electro-optic tuning. The ultra-thin transparent conducting electrode, which is fully covered on the microdisk surface, is utilized with the air-bridge wiring for the production of strong Ez and maintaining a high quality factor of 3.0 × 10 ⁴ . The produced 20μm-diameter lithium niobate microresonators possess the electro-optic tuning efficiency as high as 30.2 pm/V for TE polarization and 24.3 pm/V for TM polarization, which show obvious enhancement compared to the previous works. The highly effective electro-optic tuning of microresonators for dual polarizations offers efficient photonic platforms with the flexible use of any polarization for various photonic applications.