We report the generation and control of second harmonic generation (SHG) from a series of LaTiO₃/SrTiO₃ superlattices. We demonstrate that the nonlinear optical susceptibility χ⁽²⁾ and the SHG pattern can be tuned by tailoring the number of superlattice interfaces. Significantly, unlike the conventional ABC-type nanostructures, our AB-type nanostructures can also produce SHG signals. The χ⁽²⁾ value (24.3 pm/V) is even one to two orders of magnitude greater than the conventional ones. Hence, we demonstrate that SHG is a local microscopic process—it does not rely on macroscopic broken inversion symmetry. Moreover, we show that temperature dependence or structural phase transition can further enhance the SHG intensity. Our results introduce a scheme for SHG, extending the generation and control of SHG in nano-photonics to nearly all the accessible centrosymmetric materials.

我们报告了一系列LaTiO ₃ / SrTiO ₃超晶格的二次谐波产生（SHG）的产生和控制。我们证明，可以通过调整超晶格界面的数量来调整非线性光学磁化率χ ^（2）和SHG模式。重要的是，与传统的ABC型纳米结构不同，我们的AB型纳米结构也可以产生SHG信号。的χ ^（2）值（24.3 pm / V）甚至比常规值大一到两个数量级。因此，我们证明了SHG是局部微观过程-它不依赖于宏观破碎反演对称性。此外，我们表明温度依赖性或结构相变可以进一步提高SHG强度。我们的结果介绍了SHG的方案，将纳米光子学中SHG的生成和控制扩展到几乎所有可访问的中心对称材料。