Ultra‐Compact and Ultra‐High Speed Topological Photonic Crystal Modulator Based on Thin Film Lithium Niobate

Abstract Thin‐film lithium niobate (TFLN) modulators are indispensable components in integrated photonics. To address the demands of future dense photonic integrated circuits (PICs), a compact and high‐speed modulator is essential. However, current TFLN modulators suffer from large sizes, posing significant challenges in meeting these requirements. By leveraging the topological photonic crystal (TPhC) structure, a better optical confinement is achieved, and the interaction between the light and the TFLN is enhanced. This enables a substantial reduction in device size while simultaneously improving response speed. Therefore, an ultra‐compact and ultra‐high speed TPhC modulator based on TFLN is demonstrated. Its footprint is only 57.6 µm 2 while tuning efficiency is as high as 24.3 pm V −1 . The bandwidth of the TPhC modulator is calculated to exceed 200 GHz due to the peaking enhancement effect, while an experimental bandwidth of over 110 GHz has been measured. Clear eye diagrams for 220 Gb s −1 high‐speed signals are experimentally demonstrated, achieving a bit‐switching energy as low as 0.2 fJ.