发表机构
Politecnico di Milano; Institute of Photonic and Nanotechnology (IFN) - Consiglio Nazionale delle Ricerche (CNR); Institute of Photonics and Quantum Sciences, Heriot-Watt University; ICFO - Institut de Ciències Fotòniques, the Barcelona Institute of Science and Technology; Università degli Studi di Brescia（米兰理工大学; 光子与纳米技术研究所（IFN）- 意大利国家研究委员会（CNR）; 赫瑞-瓦特大学光子与量子科学研究所; ICFO - 巴塞罗那科学和技术理工学院光子科学研究所; 布雷西亚大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
研究连续谱中的准束缚态对介电超表面非线性光物质相互作用的影响，通过脉冲持续时间和共振耦合控制非线性自作用机制，明确不同激发 regime 及响应，模拟再现相关现象，推动其在超快和非线性纳米光子学中的应用。
AI 中文摘要
连续谱中的准束缚态可实现特殊的场限制，降低介电超表面中非线性光-物质相互作用的泵浦强度阈值。本文展示了脉冲持续时间和共振耦合如何控制非局域超表面中共振增强三次谐波产生的非线性自作用机制，识别出两种与共振模式相互作用不同的激发 regime，模拟再现了两种 regime 的情况。这些结果阐明了具有连续谱中准束缚态的超表面中的非线性自作用。
英文摘要
Quasi-bound states in the continuum (qBICs) enable exceptional field confinement, strongly reducing the pump intensity threshold for nonlinear light-matter interaction in dielectric metasurfaces. As a result, nonlinear self-action effects, often elusive in bulk nonlinear media, emerge at moderate excitation intensities. Here, nonlinear self-action in resonantly enhanced third-harmonic (TH) generation from a dielectric metasurface supporting a qBIC resonance is investigated across distinct temporal excitation regimes. These regimes establish different coupling conditions between the excitation and the resonant mode, causing the same nonlinear self-action to emerge through complementary intensity-dependent signatures. Under spectrally narrow picosecond excitation, resonance-enhanced TH generation shows pronounced deviations from cubic scaling at high intensities. In contrast, broadband femtosecond excitation transiently drives the resonance, encoding the nonlinear response in the spectral reshaping and broadening of the TH signal. Simulations reproduce both regimes: continuous-wave modeling captures picosecond power scaling and the role of higher-order nonlinear susceptibilities, while time-domain simulations resolve femtosecond dynamics. These results clarify how pulse duration, bandwidth, and resonant coupling determine the observable signatures of nonlinear self-action in resonant dielectric metasurfaces, linking field confinement to conversion efficiency, power-law scaling, and ultrafast spectral dynamics.
Comments26 pages, 14 figures
