Ion-cut lithium niobate on insulator technology: Recent advances and perspectives

Lithium niobate (LiNbO3 or LN) is a well-known multifunctional crystal that has been widely applied in various areas of photonics, electronics, and optoelectronics. In the past decade, "ion-cut" has become the key technique to produce wafer-size, high-quality, sub micrometer-thickness crystalline LiNbO3 thin films, i.e., lithium-niobate-on-insulator (LNOI). With the rapid development of LNOI technology and the tremendous progress of associated surface structuring and engineering techniques over the last few years, many novel chip-integrated LiNbO3-based devices and applications with reduced cost, complexity, power, and size, are demonstrated, boosting the resurgence of integrated photonics based on this material. The remarkable achievements are largely facilitated by the most recent technological progress in photonic integration and performance optimization of LNOI on-chip devices, such as high-quality surface domain engineering, advanced heterogeneous integration technology, powerful dispersion engineering, fine polishing lithography, and wafer-scale fabrication. Accordingly, batch-compatible chip-integrated platforms for more complex photonic integrated circuits, such as quantum optical circuits, are within reach. This article provides a timely review of the key advances in LNOI technology and a reasonable perspective on the near-future directions for both integrated photonics and applied physics communities.