512 Gbps/λ dual‐polarization thin‐film lithium niobate modulators based on an electro‐optic equalizer

Driven by the development of AI applications, optical communication systems experience an exponential surge in the demand for high data rates. Thin-film lithium niobate (TFLN) electro-optic (EO) modulators have been extensively studied and show potential for application in next-generation optical communication systems. In this paper, we present a dual-polarization (DP) TFLN EO modulator integrated based on an EO equalizer, fabricated on the lithium-niobate-on-insulator (LNOI) platform. The device consists of an 11-mm-long forward modulation section and a 4.5-mm-long reverse modulation section. It achieves a half-wave voltage (V_π) of 4 V for both Y-polarization (Y-pol) and X-polarization (X-pol), and exhibits an on-chip insertion loss of 2.5 dB for Y-pol and 2.8 dB for X-pol at a wavelength of 1,550 nm. A 3-dB EO bandwidth exceeding 110 GHz with low EO roll-off is achieved for both TE and TM modes. Furthermore, the modulator supports a data transmission rate of 512 Gbit/s in 4-level pulse amplitude modulation (PAM4) format, corresponding to 256 Gbit/s per polarization. This work demonstrates a beyond 400 G/λ solution for implementing a high-speed, and large-bandwidth modulator on a conventional LNOI platform.