Abir Tsafrir, Sideris Symeon, Ellenbogen Tal
Opt Lett. 2024 Mar 1;49(5):1241-1244. doi: 10.1364/OL.507953.
Metasurfaces, typically constructed from spatial arrangements of localized building blocks, can enhance light-matter interactions through local field enhancement or by coherent coupling to extended photonic modes. Recent works have explored how guided mode resonances influence the performance of nonlinear metasurfaces. Here we investigate the modal impact on difference-frequency generation in a waveguide-coupled metasurface platform. The system is constructed from gold split-ring resonators on a high-index TiO waveguide. We find that a symmetric configuration of the metasurface's localized modes and the extended waveguide modes lead to a modest enhancement of the downconversion process. However, when the mirror symmetry of the localized modes with respect to the guided mode propagation breaks, it introduces external chirality. This enables coupling to a higher quality mode, resulting in a 70-fold enhancement of the difference-frequency generation. The capacity to manipulate the nonlocal modes through the design offers broader control over the interaction and new avenues to tailor the nonlinear processes.
超表面通常由局部构建块的空间排列构成，可通过局部场增强或与扩展光子模式的相干耦合来增强光与物质的相互作用。近期的研究探讨了导模共振如何影响非线性超表面的性能。在此，我们研究了在波导耦合超表面平台中模态对差频产生的影响。该系统由高折射率TiO波导上的金裂环谐振器构成。我们发现，超表面局部模式与扩展波导模式的对称配置会使下转换过程略有增强。然而，当局部模式相对于导模传播的镜面对称性被打破时，会引入外在手性。这使得能够耦合到更高品质的模式，从而使差频产生增强70倍。通过设计来操纵非局部模式的能力为相互作用提供了更广泛的控制，并为定制非线性过程开辟了新途径。
