Ultra‐High‐Efficiency and Ultra‐Compact Mach–Zehnder Electro‐Optic Modulator Enabled by Topological Photonic Crystal

ABSTRACT The exponential growth of artificial intelligence (AI)‐driven data traffic is accelerating the evolution of optical interconnects toward chip‐scale integration. However, conventional electro‐optic (EO) modulators suffer from limited modulation efficiency and large device footprint, which restrict integration density and system performance. Here, by leveraging the strong slow‐light effect at the topological interface states (TIS) of the TPhC waveguide, a TPhC‐assisted EO modulator based on the Mach‐Zehnder Interferometer (MZI) was constructed, enabling the realization of an EO modulator with ultra‐high efficiency and an ultra‐compact configuration. The TPhC‐assisted‐MZI (TPhC‐A‐MZI) modulator has a compact modulation length of 63.56 µm, exhibiting a simulated modulation efficiency of 0.08 V∙cm and reaching 0.159 V∙cm in experiments. The modulator achieves a 3 dB EO bandwidth exceeding 110 GHz in both theoretical predictions and experimental measurements, with a peaking enhancement effect. We also demonstrate the transmission of 140 Gb/s non‐return‐to‐zero (NRZ) and 180 Gb/s 4‐level pulse amplitude (PAM4) modulation signals experimentally. Our proposed TPhC‐A‐MZI modulator with ultra‐high modulation efficiency and ultra‐compact structure shows great potential and paves the way for the development of high‐density, high‐speed, and large‐scale photonic integrated circuits (PICs) in the future.