Lu Chuanyi, Li Hao, Qiu Jing, Zhang Yuting, Liu Shijie, Zheng Yuanlin, Chen Xianfeng
Opt Express. 2022 Jan 17;30(2):1381-1387. doi: 10.1364/OE.447958.
Nonlinear crystalline ridge waveguides, e.g., lithium niobate-on-insulator ridge waveguides, feature high index contrast and strong optical confinement, thus dramatically enhancing nonlinear interaction and facilitating various nonlinear effects. Here, we experimentally demonstrate efficient second-harmonic generation (SHG) and cascaded fourth-harmonic generation (FHG) in a periodically poled lithium niobate (PPLN) ridge waveguide pumped with pulsed laser at the quasi-phase matching (QPM) wavelength, as well as simultaneous SHG and cascaded third-harmonic generation (THG) waves when pumped at the non-QPM wavelength. Furthermore, the ridge waveguide achieves an efficient single-pass SHG conversion efficiency of picosecond pulsed laser at ∼62%. These results may be beneficial for on-chip nonlinear frequency conversion.
非线性晶体脊形波导，例如绝缘体上铌酸锂脊形波导，具有高折射率对比度和强光学限制，从而显著增强非线性相互作用并促进各种非线性效应。在此，我们通过实验证明，在准相位匹配（QPM）波长下用脉冲激光泵浦的周期性极化铌酸锂（PPLN）脊形波导中，能实现高效的二次谐波产生（SHG）和级联四次谐波产生（FHG），以及在非QPM波长泵浦时同时产生SHG和级联三次谐波产生（THG）波。此外，该脊形波导实现了皮秒脉冲激光约62%的高效单通SHG转换效率。这些结果可能对片上非线性频率转换有益。
