Lithium-niobate microcavities have not only the ability to resonantly enhance light–matter interaction but also excellent nonlinear optical properties, thereby providing an important platform for nonlinear optical investigations. In this paper, we report the observation of multi-peak spectra in the near infrared range in lithium-niobate microcavities on a chip under the pump of a 1550 nm continuous laser. Such a multi-peak spectrum was attributed to the sum-frequency of the pump laser and its background. The conversion efficiencies of the sum-frequency processes are of the order of 61.5%W-1. The influences of the phenomenon on nonlinear processes were further discussed.

绝缘体上铌酸锂薄膜凭借铌酸锂晶体优异的光学性能和薄膜器件的易加工和可集成特性，被视为理想的集成光学平台。除了波导、调制器等传输、控制器件方面的研究之外，最近铌酸锂薄膜激光器的研究也取得了显著的进展。文中将对最近迅速发展的铌酸锂薄膜微腔激光器的研究现状进行综述。首先，介绍铌酸锂晶体和铌酸锂薄膜稀土离子掺杂的主要技术方案，以及近期有关于稀土离子掺杂铌酸锂薄膜微纳光学器件制备方面的探索；其次，总结近年来掺铒铌酸锂薄膜微盘腔、微环腔激光器方面的研究进展；然后，阐述微腔激光器体系几种常见的实现单模激光器方法的工作机理，介绍研究者们利用“游标效应”调制模式损耗等方式实现掺铒铌酸锂薄膜单模激光器的研究进展；最后，基于目前报导的铌酸锂薄膜激光器研究成果，对目前研究存在的局限性以及未来的研究方向进行了探讨。

Lithium niobate on insulator (LNOI), as an emerging and promising optical integration platform, faces shortages of on-chip active devices including lasers and amplifiers. Here, we report the fabrication of on-chip erbium-doped LNOI waveguide amplifiers based on electron beam lithography and inductively coupled plasma reactive ion etching. A net internal gain of ～30 dB/cm in the communication band was achieved in the fabricated waveguide amplifiers under the pump of a 974 nm continuous laser. This work develops new active devices on LNOI and may promote the development of LNOI integrated photonics.