发表机构
ICFO–Institut de Ciencies Fotoniques, The Barcelona Institute of Science and Technology; University of Vienna, Faculty of Physics, Vienna Center for Quantum Science and Technology (VCQ); Center for Nanophotonics, NWO Institute AMOLF; Department of Physics, Dokuz Eylül University; Centro de Física de Materiales CSIC-UPV/EHU and Materials Physics Center（ICFO-光子科学研究所，巴塞罗那科学技术研究院; 维也纳大学物理学院，维也纳量子科学与技术中心; 纳米光子学中心，NWO AMOLF研究所; 德古兹埃勒大学物理系; CSIC-巴斯克国立大学物质物理学中心和材料物理中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过原子级薄晶体银薄膜中的量子限制与等离激元共振协同作用，实现了二次谐波产生的显著增强，为超紧凑非线性光学器件提供了可扩展方案。
AI 中文摘要
现有材料固有的弱非线性光学响应，加上中心对称介质中对称性禁止的二阶过程进一步限制，严重制约了在深度亚波长、超薄体积中的高效频率转换。应对这一挑战对于非线性纳米光子学的发展至关重要。在此，我们展示了通过垂直电子量子限制与横向等离激元增强的相互作用，原子级薄、外延生长的晶体银薄膜能够规避这些限制。我们制备了表现出与电子量子阱相关的增强非线性响应的原子级薄膜，随后将其图案化为周期性纳米带和纳米三角形阵列，这些阵列支持红外局域表面等离激元共振。与未图案化的薄膜相比，这些结构中的强近场限制进一步增强了二次谐波产生。对纳米结构几何形状的精确控制使得等离激元共振的光谱调谐成为可能，从而也实现了增强谐波频率的调谐。我们的发现建立了一种在量子限制金属中激活稳健二阶非线性的方法，其中固有尺寸效应与等离激元共振协同作用。高质量外延生长与微芯片制造技术的兼容性，为片上频率转换、传感和量子光子应用中的超紧凑非线性光学元件提供了一条可扩展的路径。
英文摘要
The intrinsically weak nonlinear optical response of existing materials, further constrained by symmetry-forbidden second-order processes in centrosymmetric media, severely limits efficient frequency conversion in deeply subwavelength, ultrathin volumes. Addressing this challenge is crucial for the development of nonlinear nanophotonics. Here, we show that atomically thin, epitaxially grown crystalline silver films circumvent these restrictions through the interplay of vertical electronic quantum confinement and lateral plasmonic enhancement. We fabricate atomically thin films that exhibit an enhanced nonlinear response associated with electronic quantum wells, and subsequently pattern them into periodic nanoribbon and nanotriangle arrays sustaining infrared localized surface plasmon resonances. Strong near-field confinement in these structures further boosts second-harmonic generation compared to unpatterned films. Precise control over nanostructure geometry enables spectral tuning of the plasmonic resonance, and consequently, the enhanced harmonic frequency. Our findings establish an approach for activating robust second-order nonlinearities in quantum-confined metals, where intrinsic size effects and plasmonic resonances act synergistically. The compatibility of high-quality epitaxial growth with microchip fabrication technology offers a scalable route toward ultracompact nonlinear optical components for on-chip frequency conversion, sensing, and quantum photonic applications.
Comments16 pages, 13 figures, 47 references
