Periodically poled lithium niobate (PPLN) waveguides are a powerful platform for efficient wavelength conversion. Conventional PPLN converters, however, typically require long device lengths and high pump powers due to the limited nonlinear interaction strength. Here we use a nanostructured PPLN waveguide to demonstrate an ultrahigh normalized efficiency of $2600\%/\mathrm{W}-{\mathrm{cm}}^2$ for second-harmonic generation of 1.5 μm radiation, more than 20 times higher than that in state-of-the-art diffused waveguides. This is achieved by a combination of sub-wavelength optical confinement and high-fidelity periodic poling at a first-order poling period of 4 μm. Our highly integrated PPLN waveguides are promising for future chip-scale integration of classical and quantum photonic systems.

中文翻译：

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纳米光子周期极化铌酸锂波导中的超高效波长转换

周期性极化铌酸锂（PPLN）波导是有效波长转换的强大平台。但是，由于有限的非线性相互作用强度，传统的PPLN转换器通常需要较长的器件长度和较高的泵浦功率。在这里，我们使用纳米结构的PPLN波导来证明超高归一化效率$2600％/\mathrm{w\; ^}-{\mathrm{厘米}}^{\mathrm{2个}}$产生1.5微米辐射的二次谐波，比最新的扩散波导高20倍以上。这是通过以4μm的一阶极化周期将亚波长光学限制和高保真周期性极化相结合来实现的。我们高度集成的PPLN波导有望在未来的经典和量子光子系统芯片级集成中发挥作用。