Integrated electro-optics on thin-film lithium niobate

Electro-optics bridges electronics and photonics and serves as a foundation for a wide array of applications from communications and computing to sensing and quantum information. Integrated electro-optic approaches, in particular, enable essential electronic high-speed control for photonics while offering photonic parallelism for electronics. Recent developments in thin-film lithium niobate photonics have advanced its use for electro-optics. This technology offers not only the necessary strong electro-optic coupling but also ultralow optical loss and high microwave bandwidth. Its tight field confinement and compatibility with established nanofabrication techniques allow for excellent reconfigurability and scalability, aiding the creation of devices and systems that were deemed nearly impossible in bulk systems. Building on this platform, various new electro-optic devices have emerged, which surpass the current state of the art and introduce functionalities that previously did not exist. Thin-film lithium niobate provides a unique platform to explore various areas of physics, including photonic non-Hermitian synthetic dimensions, active topological physics and quantum electro-optics. In this Review, we present the fundamental principles of electro-optics, drawing connections between fundamental science and state-of-the-art technology. We discuss the accomplishments and prospects of integrated electro-optics enabled by the thin-film lithium niobate platform.