Dispersion engineered high quality lithium niobate microring resonators

Lithium niobate (LN) exhibits outstanding material properties with great potential for many applications. Recent advance in LN integrated photonics on chip-scale platforms has shown significant advantages in device engineering and functionality innovation. Precise engineering of group-velocity dispersion (GVD) is crucial for many important nonlinear photonic applications. In this paper, we demonstrate high-Q LN microring resonators, with optical Q above 1 million, whose GVD can be flexibly controlled in both normal and anomalous dispersion regimes, with a value between −0.128 ps2/m and 0.043 ps2/m in the telecom band, by controlling the device cross section and by utilizing the birefringence. We are able to achieve a small anomalous GVD of −0.015 ps2/m that is even smaller than that of a silica optical fiber. The flexible engineering of GVD paves a critical step towards broad nonlinear photonic applications in high-Q LN microring resonators.