Lithium tantalate microring cavities with a <i>Q</i> factor exceeding 10 million

Thin-film lithium niobate has attracted great interest in high-speed communication due to its unique piezoelectric and nonlinear properties. However, its high photorefraction and slow electro-optic response relaxation introduce the possibility of transmission bit errors. Recently, lithium tantalate, another piezoelectric and nonlinear material, has emerged as a promising candidate for active photonic integrated devices because of its weaker photorefraction, faster electro-optic response relaxation, higher optical damage threshold, wider transparency window, and lower birefringence compared with lithium niobate. Here, we developed an ultralow-loss lithium tantalate integrated photonic platform, including waveguides, grating couplers, and microring cavities. The measured highest optical Q factor of the microring cavities is beyond 10 7 , corresponding to the lowest waveguide propagation loss of ∼1.88 dB /m. The photorefractive effect in such lithium tantalate microring cavities was experimentally demonstrated to be 500 times weaker than that in lithium niobate microcavities. This work lays the foundation for a lithium tantalate integrated platform for achieving a series of on-chip optically functional devices, such as periodically poled waveguides, acousto-optic modulators, and electro-optic modulators.