标题： 锂铌酸盐薄膜中纳米区域极化解锁反向非线性光生成 显示英文标题

标题： Nanodomain poling unlocking backward nonlinear light generation in thin film lithium niobate

摘要： 非线性频率转换在电信、信号处理和计算应用中提供了强大的能力。 薄膜铌酸锂（TFLN）由于其强电光效应和二阶非线性，已成为一种有前途的集成光子学平台，可通过周期极化加以利用。 然而，x切向TFLN的传统极化技术仅能实现微米量级的最小周期尺寸，这阻碍了涉及反向传播波的有效相互作用的生成。 在此，我们报告了x切向TFLN的可扩展周期极化，周期小至215纳米，并实现了用于反向和后向传播相位匹配的器件。 我们估计转换效率分别为1474$\%$/W/cm$^2$和45$\%$/W/cm$^2$，通过测量和频生成，我们确认非线性生成发生在期望的方向。 我们报告了反向传播的自发参量下转换，并首次报告了后向传播器件的自发参量下转换。 这一技术进步实现了对TFLN中域几何的前所未有的精确控制，并导致了具有为量子信号处理、量子计算和计量学量身定制的空间和光谱特性的光子对的生成。 显示英文摘要

摘要： Nonlinear frequency conversion offers powerful capabilities for applications in telecommunications, signal processing, and computing. Thin-film lithium niobate (TFLN) has emerged as a promising integrated photonics platform due to its strong electro-optic effect and second-order nonlinearity, which can be exploited through periodic poling. However, conventional poling techniques in x-cut TFLN are limited to minimum period sizes on the order of microns, preventing the efficient generation of interactions involving counter-propagating waves. Here we report scalable periodic poling of x-cut TFLN with periods down to 215 nm and realize devices for counter- and back-propagating phase matching. We estimate conversion efficiencies of 1474 $\%$/W/cm$^2$ and 45 $\%$/W/cm$^2$ respectively, and measuring sum frequency generation we confirm that the nonlinear generation takes place in the desired direction. We report spontaneous parametric down conversion for the counter-propagating and, for the first time, for a backward propagating device. This technological advance provides the control of domain geometry in TFLN with an unprecedented precision and leads into the generation of photon pairs with spatial and spectral properties tailored for quantum signal processing, quantum computing and metrology.