近日，法国巴黎城市大学和法国国家科学研究中心的Giuseppe Leo及其研究团队取得一项新进展。经过不懈努力，他们利用介质超表面揭示设计型涡旋的非线性生成机制。相关研究成果已于2025年1月16日在国际知名学术期刊《光：科学与应用》上发表。

本文展示并分析了通过介质超全息图生成高纯度二次谐波（SH）光学涡旋的方法。通过全波模拟和适当的制造工艺，研究人员实现了将非结构化泵浦光束高效地倍频为拓扑荷从1到10的二次谐波涡旋。得益于对二次谐波相位的准局部控制，干涉测量和模态纯度测量证实了所生成的二次谐波涡旋质量高，与设计意图的偏差极小。

通过对实验数据和半解析计算的系统比较，研究人员还深入揭示了超表面生成的谐波光束中出现幽灵涡旋的现象，强调了简单设计的重要性，这种设计可以轻松地以高保真度转化为实际制造的设备。这项研究结果凸显了非线性介质超表面在多功能结构化光生成和操控方面的潜力，为集成光子系统的未来发展铺平了道路。

据悉，涡旋光束目前正吸引着从基础研究到多个有前景应用领域的广泛关注。尽管其在笨重光学器件中的生成限制了其在集成复杂系统中的应用，但超表面最近在产生光学涡旋方面已被证明是成功的，尤其是在线性领域。在对于经典和量子信息未来具有战略重要性的非线性领域，迄今为止，轨道角动量的产生仅停留在定性层面，且尚未讨论设计与实验结果之间的差异。

附：英文原文

Title: Unravelling the nonlinear generation of designer vortices with dielectric metasurfaces

Author: Coudrat, Laure, Boulliard, Guillaume, Grard, Jean-Michel, Lematre, Aristide, Degiron, Aloyse, Leo, Giuseppe

Issue&Volume: 2025-01-16

Abstract: Vortex beams are currently drawing a great deal of interest, from fundamental research to several promising applications. While their generation in bulky optical devices limits their use in integrated complex systems, metasurfaces have recently proven successful in creating optical vortices, especially in the linear regime. In the nonlinear domain, of strategic importance for the future of classical and quantum information, to date orbital angular momentum has only been created in qualitative ways, without discussing discrepancies between design and experimental results. Here, we demonstrate and analyze the generation of high-purity second harmonic (SH) optical vortices via dielectric meta-holograms. Through full-wave simulations and a proper fabrication protocol, we achieve efficient frequency doubling of an unstructured pump beam into SH vortices with topological charges from 1 to 10. Interferometric and modal-purity measurements confirm the generation of high-quality SH vortices with minimal deviations from the intended design thanks to a quasi-local control over the SH phase. Through systematic comparisons between experimental data and semi-analytical calculations, we also provide a clear insight into the occurrence of ghost vortices in the metasurface-generated harmonic beams, highlighting the importance of simple designs that can be readily transposed into fabricated devices with high fidelity. Our findings underscore the potential of nonlinear dielectric metasurfaces for versatile structured-light generation and manipulation, paving the way for future developments in integrated photonic systems.

DOI: 10.1038/s41377-025-01741-0

Source: https://www.nature.com/articles/s41377-025-01741-0