[2] [2] CHEN Kunfeng, WU Jian, HU Qianyu, et al. Omni-functional crystal: Advanced methods to characterize the composition and homogeneity of lithium niobate melts and crystals［J］. Exploration, 2022, 2(4): 20220059.

[6] [6] ZHOU Chao, MA Jianan, XIANG Xiaoyi, et al. Femtosecond laser processing of lithium niobate crystal: principle and applications［J］. Prog Phys, 2020, 40(3): 69-83.

[7] [7] BURROWS L, Now entering, Lithium Niobate Valley. 2017; Available from: https://www.seas.harvard.edu/news/2017/12/now-entering-lithium- niobate-valley.

[8] [8] YAN Zhiwei, WANG Qiang, XIAO Meng, et al. Probing rotated weyl physics on nonlinear lithium niobate-on-insulator chips［J］. Phys Rev Lett, 2021, 127(1): 013901.

[9] [9] CHIH-LIN I, HAN Sen, and BIAN Shuangfeng. Energy-efficient 5G for a greener future［J］. Nature Electron, 2020, 3(4): 182-184.

[10] [10] ZHANG Bin, LI Lingqi, WANG Lei, et al. Second harmonic generation in femtosecond laser written lithium niobate waveguides based on birefringent phase matching［J］. Opt Mater, 2020, 107: 110075.

[11] [11] POHL D, M REIG ESCALé, M MADI, et al. An integrated broadband spectrometer on thin-film lithium niobate［J］. Nature Photon, 2019, 14(1): 24-29.

[12] [12] WANG Cheng, ZHANG Mian, CHEN Xi, et al. Integrated lithium niobate electro-optic modulators operating at CMOS-compatible voltages［J］. Nature, 2018, 562(7725): 101-104.

[13] [13] WANG Ceng, ZHANG Mian, YU Mengjie, et al. Monolithic lithium niobate photonic circuits for Kerr frequency comb generation and modulation［J］. Nat Commun, 2019, 10(1): 978.

[14] [14] XU Mengyue, HE Mingbo, ZHANG Hongguang, et al. High-performance coherent optical modulators based on thin-film lithium niobate platform［J］. Nat Commun, 2020, 11(1): 3911.

[15] [15] ZHANG Mian, BUSCAINO B, WANG Cheng, et al. Broadband electro-optic frequency comb generation in a lithium niobate microring resonator［J］. Nature, 2019, 568(7752): 373-377.

[18] [18] SHI Guoqiang, XUE Dongfeng. A multiscale view in functional materials［J］. Pro Nat Sci-Mater, 2023. DOI: 10.1016/j.pnsc.2022.09.017.

[19] [19] SHI Guoqiang, XUE Dongfeng. Perspective on multiple degrees of freedom in crystal materials［J］. Sci China Technol Sc, 2022, 65(11): 2787-2789.

[20] [20] KONG Yongfa, BO Fang, WANG Weiwei, et al. Recent progress in lithium niobate: Optical damage, defect simulation, and on-chip devices［J］. Adv Mater, 2020, 32(3): e1806452.

[21] [21] SCHMIDT F, A L KOZUB, U GERSTMANN, et al. Electron polarons in lithium niobate: Charge localization, lattice deformation, and optical response［J］. Crystals, 2021, 11(5): 542.

[22] [22] BHATT R, I BHAUMIK, S GANESAMOORTHY, et al. Control of intrinsic defects in lithium niobate single crystal for optoelectronic applications［J］. Crystals, 2017, 7(2): 23.

[23] [23] PETERSON G, and CARNEVALE A. 93Nb NMR Linewidths in nonstoichiometric lithium niobate［J］. J Chem Phys, 1972, 56, 4848.

[24] [24] KSTERS M, B STURMAN, P WERHEIT, et al. Optical cleaning of congruent lithium niobate crystals［J］. Nature Photon, 2009, 3(9): 510-513.

[25] [25] GOPALAN V, T E MITCHELL, Y FURUKAWA, et al. The role of nonstoichiometry in 180° domain switching of LiNbO3 crystals［J］. Appl Phys Lett, 1998, 72(16): 1981-1983.

[26] [26] CHEN Kunfeng, LI Yanlu, PENG Chao, et al. Microstructure and defect characteristics of lithium niobate with different Li concentrations［J］. Inorg Chem Front, 2021, 8(17): 4006-4013.

[27] [27] HE Xiangke, XUE Dongfeng, KITAMURA K. Defects and domain engineering of lithium niobate crystals［J］. Mater Sci Eng: B, 2005, 120(1-3): 27-31.

[29] [29] XUE Dongfeng, BETZLER K.Influence of optical-damage-resistant dopants on the nonlinear optical properties of lithium niobate［J］. Appl Phys B, 2014, 72(6): 641-645.

[30] [30] XUE Dongfeng, BETZLER K, HESSE H. Chemical bond analysis of the second order nonlinear optical behavior of Zn-doped lithium niobate［J］. Opt Commun, 2000, 182(1-3): 167-173.

[31] [31] XUE Dongfeng, BETZLER K, HESSE H. Induced Li-site vacancies and non-linear optical behavior of doped lithium niobate crystals［J］. Opt Mater, 2001, 16(3): 381-387.

[32] [32] XUE Dongfeng HE Xiangke. Dopant occupancy and structural stability of doped lithium niobate crystals［J］. Phys Rev B, 2006, 73(6): 064113.

[33] [33] XUE Dongfeng, IYI N, KITAMURA K. Influence of temperature on the structure and charge distribution of lithium niobate single crystals［J］. Jpn J Appl Phys, 2002, 41(11B): 7029-7032.

[34] [34] XUE Dongfeng, KITAMURA K. Dielectric characterization of the defect concentration in lithium niobate single crystals［J］. Solid State Commun, 2002, 122(10): 537-541.

[35] [35] XUE Dongfeng, KITAMURA K. An estimation of nonlinear optical properties of lithium niobate family ferroelectrics by the chemical bond model［J］. Jpn J Appl Phys, 2003, 42(Part 1, No. 9B): 6230-6233.

[36] [36] XUE Dongfeng, KITAMURA K. Compositional dependence of cationic displacements in lithium niobate and lithium tantalate crystals［J］. J Phys Chem Solids, 2005, 66(2-4): 585-588.

[37] [37] ZHANG Xu, XUE Dongfeng. Bond energy prediction of Curie temperature of lithium niobate crystals［J］. J Phys Chem B, 2007, 111(10): 2587-2590.

[38] [38] FONTANA M D, BOURSON P. Microstructure and defects probed by Raman spectroscopy in lithium niobate crystals and devices［J］. Appl Phys Rev, 2015, 2(4): 040602.

[39] [39] XU Hankun, LIN Kun, LI Wenjie, et al. Local structure manipulates nonlinear optical properties in non-stoichiometric lithium niobate［J］. J Phys Chem C, 2022, 126(34): 14735-14741.

[40] [40] ROSHCHUPKIN D V, ROSHCHUPKINA H D, IRZHAK D V, et al. X-ray topography analysis of acoustic wave fields in the SAW-resonator structures［J］. T-UFFC, 2005, 52(11): 2081-2087.

[41] [41] CAPELLE B, DETAINT J, EPELBOIN Y, et al. Crystalline quality of the trigonal piezoelectric materials and effects of the extended defects［J］. T-UFFC, 2012, 59(5): 1013-1022.

[42] [42] CASTILLA H de, BLANGER P, ZEDNIK RICARDO J. High temperature characterization of piezoelectric lithium niobate using electrochemical impedance spectroscopy resonance method［J］. J Appl Phys, 2017, 122: 244103.

[43] [43] FRANKE I, TALIK E, ROLEDER K, et al. Temperature stability of elastic and piezoelectric properties in LiNbO3 single crystal［J］. J Phys D: Appl Phys, 2005, 38: 4308-4312

[44] [44] NATAF G F, AKTAS O, GRANZOW T, et al. Influence of defects and domain walls on dielectric and mechanical resonances in LiNbO3［J］. J Phys: Condens Matter, 2016, 28: 015901.

[45] [45] GONNISSEN J, BATUK D, NATAF G F, et al. Direct observation of ferroelectric domain walls in LiNbO3: Wall-meanders, kinks, and local electric charges［J］. Adv Funct Mater, 2016, 26: 7599-7604.

[47] [47] Du Wanying, Zhang Zibo, Xu Jiaqi, et al. Electro-optic property of Ti4+-doped LiNbO3 single crystal［J］. Opt Mater Exp, 2016, 6(8): 2593-2599.

[49] [49] FURUKAWA Y, KITAMURA K, TAKEKAWA S, et al. Photorefraction in LiNbO3 as a function of ［Li］/［Nb］ and MgO concentrations［J］. Appl Phys Lett 2000, 77(16): 2494-2496.

[51] [51] HE Yali, XUE Dongfeng. Bond-energy study of photorefractive properties of doped lithium niobate crystals［J］. J Phys Chem C 2007, 111(35): 13238-13243.

[52] [52] SCHWESYG J R., MARKOSYAN A, FALK M, et al. Optical loss mechanisms in magnesium-doped lithium niobate crystals in the 300 to 2950 nm wavelength range［C］//Advances in Optical Materials. Optical Society of America, Istanbul, Turkey, 2011: AIThE3.

[53] [53] SCHWESYG J R, KAJIYAMA M C C, FALK M, et al. Light absorption in undoped congruent and magnesium-doped lithium niobate crystals in the visible wavelength range［J］. Appl Phys B. 2010(100): 109-115.

[54] [54] FURUKAWA Y, KITAMURA K, ALEXANDROVSKI A, et al. Green-induced infrared absorption in MgO doped LiNbO3［J］. Appl Phys Lett, 2001, 78(14): 1970-1972.