Beyond 110 GHz Electro‐Optic Slow‐Light Modulation via Cascaded One‐Dimensional Topological Edge States on Thin‐Film Lithium Tantalate

ABSTRACT High‐speed and broadband electro‐optic modulators are crucial for next‐generation optical interconnects, yet conventional designs face a trade‐off between modulation bandwidth and efficiency. Here, we exploit and implement superlattice structures on thin‐film lithium tantalate to achieve slow‐light‐enhanced electro‐optic modulation with a flat broadband response by cascading 1D topological edge states while maintaining strong field confinement, overcoming the dispersion and bandwidth limitations of conventional slow‐light structures. Leveraging the topological slow‐light effect and capacitively loaded slow‐wave electrodes on a thin‐film lithium tantalate platform, the modulator exhibits co‐optimized performance, with significant improvements in the modulation efficiency V π L of 0.64 V∙cm and bandwidth of >110 GHz without roll‐off. This approach uniquely enables a synergy between the strongly confined topological slow‐light mode and traveling‐wave microwave signal, achieving good electro‐optic velocity and impedance matching. Moreover, non‐return‐to‐zero and four‐level pulse amplitude modulation signals of 120 and 220 Gbps data rates are generated by the topological modulator, respectively. This work demonstrates a promising route for integrating topological photonics with compact, high‐speed, and broadband electro‐optic modulators for next‐generation broadband optical communication and signal processing systems.