Integrated photon-pair sources are crucial for scalable photonic quantum systems. Thin-film lithium niobate is a promising platform for on-chip photon-pair generation through spontaneous parametric down-conversion (SPDC). However, the device implementation faces practical challenges. Periodically poled lithium niobate (PPLN), despite enabling flexible quasi-phase matching, suffers from poor fabrication reliability and device repeatability, while conventional modal phase matching (MPM) methods yield limited efficiencies due to inadequate mode overlaps. Here, we introduce a layer-poled lithium niobate (LPLN) nanophotonic waveguide for efficient photon-pair generation. It leverages layer-wise polarity inversion through electrical poling to break spatial symmetry and significantly enhance nonlinear interactions for MPM, achieving a notable normalized second-harmonic generation (SHG) conversion efficiency of 4615% W⁻¹cm⁻². Through a cascaded SHG and SPDC process, we demonstrate photon-pair generation with a normalized brightness of 3.1 × 10⁶ Hz nm⁻¹ mW⁻² in a 3.3 mm long LPLN waveguide, surpassing existing on-chip sources under similar operating configurations. Crucially, our LPLN waveguides offer enhanced fabrication reliability and reduced sensitivity to geometric variations and temperature fluctuations compared to PPLN devices. We expect LPLN to become a promising solution for on-chip nonlinear wavelength conversion and non-classical light generation, with immediate applications in quantum communication, networking, and on-chip photonic quantum information processing.

集成光子对源对于可扩展的光子量子系统至关重要。薄膜铌酸锂是通过自发参量下转换（SPDC）产生片上光子对的有前途的平台。然而，设备的实现面临着实际挑战。周期性极化铌酸锂（PPLN）尽管能够实现灵活的准相位匹配，但其制造可靠性和器件可重复性较差，而传统的模态相位匹配（MPM）方法由于模式重叠不足而效率有限。在这里，我们引入了一种层极化铌酸锂（LPLN）纳米光子波导，用于有效产生光子对。它通过电极化利用分层极性反转来打破空间对称性并显着增强 MPM 的非线性相互作用，实现显着的归一化二次谐波产生 (SHG) 转换效率 4615% W ^-1 cm ^-2 。通过级联SHG和SPDC工艺，我们在3.3毫米长的LPLN波导中展示了归一化亮度为3.1 × 10 ⁶ Hz nm ^-1 mW ^-2的光子对生成，在类似的操作配置下超越了现有的片上源。至关重要的是，与 PPLN 器件相比，我们的 LPLN 波导具有更高的制造可靠性，并降低了对几何变化和温度波动的敏感性。我们预计 LPLN 将成为片上非线性波长转换和非经典光产生的有前途的解决方案，并立即应用于量子通信、网络和片上光子量子信息处理。