发表机构
University of Southern Denmark; Eastern Institute of Technology（南丹麦大学; 东方理工大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
提出一种铌酸锂上超表面架构，将二次谐波产生与波前整形分离，实现自旋解耦的光束偏转和自旋复用全息，为非线性超光学提供可扩展平台。
AI 中文摘要
非线性超表面（NMSs）能够利用超薄纳米光子平台同时产生和操控谐波光。然而，传统非线性超表面通常采用单片单层结构，其中频率转换、偏振选择和波前工程相互交织，在同一非线性超原子内同时发生，使得这些功能本质上相互依赖，并对材料选择、结构对称性和可用的几何参数空间施加了限制。在此，我们提出并实验验证了一种铌酸锂上超表面架构，该架构将谐波光的产生与波前操控在物理上分离开来。在该平台中，z切薄膜铌酸锂（LN）层凭借其固有的体二次非线性作为自旋选择性二次谐波源，而覆盖其上的介质超表面随后独立地塑造所产生的谐波场的波前。这一两步过程，由于谐波产生与波前整形解耦，消除了与传统非线性超原子相关的对称性限制，并使得成熟的线性超表面设计策略能够直接应用于谐波波前工程。作为概念验证演示，我们实现了自旋解耦的二次谐波光束偏转和自旋复用全息术，实现了将具有正交自旋态的谐波信号高对比度路由到不同衍射通道，以及独立全息图像的高保真重建。通过将谐波波前控制从超原子工程转向模块化系统级设计，我们的方法为集成非线性超光学开辟了一条通用途径，并为先进光学功能提供了一个可扩展的平台。
英文摘要
Nonlinear metasurfaces (NMSs) enable simultaneous generation and manipulation of harmonic light with ultrathin nanophotonic platforms. However, conventional NMSs typically adopt a monolithic single-layer configuration in which frequency conversion, polarization selection and wavefront engineering are intertwined to simultaneously occur within the same nonlinear meta-atoms, making these functionalities intrinsically interdependent and imposing constraints on material choice, structural symmetry, and the available geometric parameter space. Here, we propose and experimentally demonstrate a metasurface-on-lithium-niobate architecture that physically separates harmonic light generation and wavefront manipulation. In this platform, a z-cut thin-film LN layer serves as a spin-selective second-harmonic source through its intrinsic bulk second-order nonlinearity, while an overlaid dielectric metasurface subsequently and independently molds wavefronts of generated harmonic fields. The two-step process, by virtue of harmonic generation being decoupled from wavefront shaping, removes symmetry constraints associated with conventional nonlinear meta-atoms and enables the direct transfer of well-established linear metasurface design strategies to harmonic wavefront engineering. As proof-of-concept demonstrations, we realize spin-decoupled second-harmonic beam steering and spin-multiplexed holography, achieving high-contrast routing of harmonic signals with orthogonal spin states into distinct diffraction channels and high-fidelity reconstruction of independent holographic images. By redirecting the harmonic wavefront control from the meta-atom engineering to the modular system-level design, our approach establishes a versatile route toward integrated nonlinear meta-optics and provides a scalable platform for advanced optical functionalities.
