We numerically investigate the low-voltage electro-optic (EO) switching at a telecommunication wavelength and modulation of second harmonic generation (SHG) in lithium niobate (LN) resonant waveguide gratings (RWGs) working at quasi-bound states in the continuum (BICs). The external applied voltage V₀ = 0.4 V can realize the transmission changing from near zero at V₀ = 0 to 70 % in the feasible RWGs nanostructure at quasi-BICs wavelength under both TM-and TE-polarization. The tuning efficiency, i.e. the shift of resonance wavelength at external per-voltage, arrives up to 121 pm/V and 56 pm/V under TM- and TE-polarization, respectively. Besides the switching of linear transmission, SHG from the LN RWGs is also effectively modulated by external voltages. Several orders of magnitude change in SHG conversion efficiency are achieved for the external voltage varying from V₀ = 0 V to 1 V. The low-voltage switching, high tuning efficiency and dramatical modulation of SHG are ascribed to the ultra-high Q-factor at quasi-BICs which is sensitively affected by the refractive index of LN based on EO effect. The results show that the LN RWGs nanostructure working at quasi-BICs is promising for the application in high-performance EO linear and nonlinear devices.

我们数值研究了通信波长下的低压电光 (EO) 开关和铌酸锂 (LN) 谐振波导光栅 (RWG) 中工作在连续体准束缚态 (BIC) 中二次谐波产生 (SHG) 的调制). 外加电压V ₀  = 0.4 V可实现传输从V _{0接近零变化} = 0 到 70% 在可行的 RWGs 纳米结构中，在 TM 和 TE 偏振下的准 BICs 波长。调谐效率，即谐振波长在外部电压下的偏移，在 TM 和 TE 偏振下分别达到 121 pm/V 和 56 pm/V。除了线性传输的切换外，来自 LN RWG 的 SHG 还受到外部电压的有效调制。对于从V ₀ = 0 V 到 1 V变化的外部电压，SHG 转换效率实现了几个数量级的变化。SHG 的低压开关、高调谐效率和显着调制归因于超高Q-准 BIC 的因子，它受基于 EO 效应的 LN 折射率的敏感影响。结果表明，在准 BICs 工作的 LN RWGs 纳米结构有望应用于高性能 EO 线性和非线性器件。