Cavity-Enhanced Acousto-Optic Modulators on Polymer-Loaded Lithium Niobate Integrated Platform

On-chip acousto-optic (AO) modulation represents a significant advancement in the development of highly integrated information processing systems. However, conventional photonic devices face substantial challenges in achieving efficient conversion due to the limited overlap between acoustic waves and optical waves. In this study, we address this limitation by demonstrating an enhanced conversion effect of photonic crystal nanobeam cavity (PCNBC) in AO modulation on a polymer-loaded lithium niobate integrated platform. Attributed to the high quality factor to mode volume ratio (Q/V) and optimal light-sound overlap within the nanocavity, PCNBC-based AO modulator exhibits a significantly enhanced extinction ratio of 38 dB with a threshold RF power below -50 dBm, which is two orders of magnitude lower than that based on microring resonator (MRR). In addition, robust digital amplitude shift keying modulations were performed using selected RF and optical channels of the PCNBC-enhanced AO modulators. These findings validate the compelling properties of the PCNBC photonic platform, establishing it as a promising candidate for on-chip integrated microwave photonics, optical transceivers, and computing applications.