基于绝缘体上铌酸锂平台，设计了周期极化的铌酸锂薄膜波导结构，利用铌酸锂良好的非线性性质并结合灵活的相位匹配方案，分析了结构色散对极化周期的影响。此外，借助波导模式有效折射率随温度变化的不同，通过改变材料温度，有效扩展了频率转换的带宽，实现了1.5 ~1.6 μm范围内的倍频，最终获得562%的归一化转换效率，为芯片光子学参量转换的进一步研究提供了理论基础。

Lithium niobate (LN) thin film has received much attention as an integrated photonic platform, due to its rich and great photoelectric characteristics, based on which various functional photonic devices, such as electro-optic modulators and nonlinear wavelength converters, have been demonstrated with impressive performance. As an important part of the integrated photonic system, the long-awaited laser and amplifier on the LN thin-film platform have made a series of breakthroughs and important progress recently. In this review paper, the research progress of lasers and amplifiers realized on lithium niobate thin film platforms is reviewed comprehensively. Specifically, the research progress on optically pumped lasers and amplifiers based on rare-earth ions doping of LN thin films is introduced. Some important parameters and existing limitations of the current development are discussed. In addition, the implementation scheme and research progress of electrically pumped lasers and amplifiers on LN thin-film platforms are summarized. The advantages and disadvantages of optically and electrically pumped LN thin film light sources are analyzed. Finally, the applications of LN thin film lasers and amplifiers and other on-chip functional devices are envisaged.

铌酸锂薄膜调制器具有体积小、带宽高、半波电压低的优点，在光纤通讯和光纤传感领域具有重要应用价值，是近年来的研究热点。本文梳理了铌酸锂薄膜调制器的波导结构、耦合结构、电极结构的研究进展，总结了LN薄膜波导的制备工艺，并深入分析了不同结构调制器的性能。基于SOI和LNOI结构，薄膜调制器实现了V_πL<2 V∙cm，双锥形耦合方案实现了耦合损耗<0.5 dB/facet，行波电极结构实现了调制带宽>100 GHz。铌酸锂薄膜调制器的性能在大多数方面优于目前商用铌酸锂调制器，随着波导工艺进一步提升，将成为铌酸锂调制器的热门方案。最后对铌酸锂薄膜调制器的发展趋势和应用前景进行了展望。

The heterogeneous integration of silicon thin film and lithium niobate (LN) thin film combines both the advantages of the excellent electronics properties and mature micro-processing technology of Si and the excellent optical properties of LN, comprising a potentially promising material platform for photonic integrated circuits. Based on ion-implantation and wafer-bonding technologies, a 3 inch wafer-scale hybrid mono-crystalline Si/LN thin film was fabricated. A high-resolution transmission electron microscope was used to investigate the crystal-lattice arrangement of each layer and the interfaces. Only the H-atom-concentration distribution was investigated using secondary-ion mass spectroscopy. High-resolution X-ray-diffraction ω–2θ scanning was used to study the lattice properties of the Si/LN thin films. Raman measurements were performed to investigate the bulk Si and the Si thin films. Si strip-loaded straight waveguides were fabricated, and the optical propagation loss of a 5-μm-width waveguide was 6 dB/cm for the quasi-TE mode at 1550 nm. The characterization results provide useful information regarding this hybrid material.

We use the nonlinear coupled-mode theory to theoretically investigate second-harmonic generation (SHG) in subwavelength x-cut and z-cut lithium niobate (LN) thin-film waveguides and derive the analytical formula to calculate SHG efficiency in x-cut and z-cut LN thin-film waveguides explicitly. Under the scheme of optimal modal phase matching (MPM), two types of LN thin films can achieve highly efficient frequency doubling of a 1064 nm laser with a comparable conversion efficiency due to very consistent modal field distribution of the fundamental wave and second-harmonic wave with efficient overlap between them. Such a robust MPM for high-efficiency SHG in both the subwavelength x-cut and z-cut LN thin-film waveguides is further confirmed in a broad wavelength range, which might facilitate design and application of micro–nano nonlinear optical devices based on the subwavelength LN thin film.