We propose a scheme for the generation of counterpropagating polarization-entangled photon pairs from a periodically poled lithium niobate on insulator waveguide. The waveguide is designed to enable a special dispersion relationship between the ${{\rm TM}_{00}}$ and ${{\rm TE}_{00}}$ modes that allows two concurrent counterpropagating quasi-phase-matching type-II spontaneous parametric downconversion processes with a single reciprocal wave vector. Due to the counterpropagating phase-matching geometry, the source has a narrow bandwidth in the order of several gigahertz. The compact source opens up a new method for integrated photonic technologies.

中文翻译：

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基于绝缘体上薄膜铌酸锂的窄带反向传播偏振纠缠光子对

我们提出了一种方案，用于从绝缘体波导上的周期性极化铌酸锂生成反向传播的偏振纠缠光子对。波导旨在实现$ {{\ rm TM} _ {00}} $和$ {{rmrm}} {{00}} $模式之间的特殊色散关系，从而允许两个并发的反向传播准相位匹配具有单个互易波矢量的II型自发参数下变频过程。由于反向传播的相位匹配几何形状，光源的带宽窄至几千兆赫兹。紧凑的光源为集成光子技术开辟了一种新方法。