ARTICLE High-performance coherent optical modulators based on thin-film lithium niobate platform Mengyue Xu 1 , Mingbo He 1 , Hongguang Zhang 2,3 , Jian Jian 1 , Ying Pan 1 , Xiaoyue Liu 1 , Lifeng Chen 1 , Xiangyu Meng 1 , Hui Chen 1 , Zhaohui Li 1 , Xi Xiao 2,3 ✉ , Shaohua Yu 2,3 , Siyuan Yu 1 & Xinlun Cai 1 ✉ The coherent transmission technology using digital signal processing and advanced mod- ulation formats, is bringing networks closer to the theoretical capacity limit of optical fibres, the Shannon limit. The in-phase/quadrature electro-optic modulator that encodes informa- tion on both the amplitude and the phase of light, is one of the underpinning devices for the coherent transmission technology. Ideally, such modulator should feature a low loss, low drive voltage, large bandwidth, low chirp and compact footprint. However, these require- ments have been only met on separate occasions. Here, we demonstrate integrated thin-film lithium niobate in-phase/quadrature modulators that fulfil these requirements simulta- neously. The presented devices exhibit greatly improved overall performance (half-wave voltage, bandwidth and optical loss) over traditional lithium niobate counterparts, and sup- port modulation data rate up to 320 Gbit s -1 . Our devices pave new routes for future high- speed, energy-efficient, and cost-effective communication networks. https://doi.org/10.1038/s41467-020-17806-0 OPEN 1 State Key Laboratory of Optoelectronic Materials and Technologies and School of Electronics and Information Technology, Sun Yat-sen University, 510006 Guangzhou, China. 2 National Information Optoelectronics Innovation Center, China Information and Communication Technologies Group Corporation (CICT), 430074 Wuhan, China. 3 State Key Laboratory of Optical Communication Technologies and Networks, China Information and Communication Technologies Group Corporation (CICT), 430074 Wuhan, China. ✉ email: xxiao@wri.com.cn; caixlun5@mail.sysu.edu.cn NATURE COMMUNICATIONS | (2020)11:3911 | https://doi.org/10.1038/s41467-020-17806-0 | www.nature.com/naturecommunications 1 1234567890():,;