1State Key Laboratory of Advanced Optical Communication Systems and Networks, School of Physics and Astronomy, Shanghai Jiao Tong University, Shanghai 200240, China
2Shanghai Research Center for Quantum Sciences, Shanghai 201315, China
3Jinan Institute of Quantum Technology, Jinan, Shandong 250101, China
4Collaborative Innovation Center of Light Manipulation and Applications, Shandong Normal University, Jinan, Shandong 250358, China
The lithium niobate crystal is a multifunctional optical material with excellent comprehensive properties. For the past decades, lithium niobate crystal has attracted significant attention in optics researches. Recently, lithium niobate on insulator (LNOI), also known as lithium niobate thin film (LNTF), has been considered as a revolutionary technology in optics that rejuvenates lithium niobate for LNOI-based integrated photonics. A LNTF is irreplaceable in frequency conversion since it is one of the best nonlinear crystals. In this study, we summarize the most recent progress of LNTF in nonlinear frequency conversions, such as second-order nonlinearities, third-order nonlinearities, cascaded nonlinearities, and optical frequency comb. Finally, we present the prospect for photonic integrated circuits (PIC) on the LNOI platform.