Photonic crystal microring resonators on a hybrid silicon nitride-on-lithium niobate platform

Photonic crystal resonators (PhCRs) have been widely used in nonlinear integrated photonics for frequency engineering applications. A microwave-assisted frequency converter based on PhCRs provides precisely controlled bidirectional frequency conversion. Using a hybrid silicon nitride-on-lithium niobate-on-insulator platform, we demonstrate a high-quality PhCR for the first time, to the best of our knowledge, for voltage-driven flexible frequency conversion using the electro-optic effect (0.85 pm/V) without etching lithium niobate. The fabricated PhCR has a large supermode splitting bandwidth of 14.6 GHz and an intrinsic quality factor of 1.47 × 10⁵. Using different periodic corrugation amplitudes in the fabricated PhCRs enables the precise control of mode-splitting bandwidth with a 93.5-MHz/nm bandwidth-to-amplitude ratio.