Liu Shijie, Zheng Yuanlin, Chen Xianfeng
Opt Lett. 2017 Sep 15;42(18):3626-3629. doi: 10.1364/OL.42.003626.
Whispering-gallery-mode (WGM) microcavities are very important in both fundamental science and practical applications, among which on-chip second-order nonlinear microresonators play an important role in integrated photonic functionalities. Here we demonstrate resonant second-harmonic generation (SHG) and cascaded third-harmonic generation (THG) in a lithium niobate-on-insulator (LNOI) microdisk resonator. Efficient SHG in the visible range was obtained with only several mW input powers at telecom wavelengths. THG was also observed through a cascading process, which reveals simultaneous phase matching and strong mode coupling in the resonator. Cascading of second-order nonlinear processes gives rise to an effectively large third-order nonlinearity, which makes on-chip second-order nonlinear microresonators a promising frequency converter for integrated nonlinear photonics.
回音壁模式（WGM）微腔在基础科学和实际应用中都非常重要，其中片上二阶非线性微谐振器在集成光子功能中发挥着重要作用。在此，我们展示了绝缘体上铌酸锂（LNOI）微盘谐振器中的共振二次谐波产生（SHG）和级联三次谐波产生（THG）。在电信波长下仅输入几毫瓦的功率，就获得了可见光范围内的高效SHG。通过级联过程还观察到了THG，这揭示了谐振器中同时存在的相位匹配和强模式耦合。二阶非线性过程的级联产生了有效的大三阶非线性，这使得片上二阶非线性微谐振器成为集成非线性光子学中一种很有前景的频率转换器。
