AI 中文总结
该工作提出一套自洽的Floquet-Bloch理论，统一处理空间周期性、非绝热时间调制和材料色散，以因果方式描述色散时变超表面的散射与模态结构，并经全波仿真验证，揭示了激子谐波增强和光子时间晶体中动量带隙的物理机制。
AI 中文摘要
时变超表面中的光与物质相互作用产生了超越静态系统极限的现象。时间调制使得光与物质之间能够进行能量交换，电磁场在动量和频率上均发生耦合，这对广泛的光子学应用具有重要意义。然而，要精确描述此类系统，需要一种能够捕捉时空变化交织效应并以因果方式考虑色散的理论，因为实际光学材料表现出频率依赖的响应和有限的时域记忆。本文发展了一套自洽的Floquet-Bloch理论，用于捕捉色散时变超表面的响应，通过物理上一致的构成关系保证因果性。该理论在统一框架内处理空间周期性、非绝热时间调制和材料色散，不仅能够获取超表面的散射响应，还能揭示其固有的模态结构。该公式通过全波仿真得到验证。作为示例，首先将其应用于激子时变超表面中的非对称Floquet谐波产生，其中激子色散实现了选择性谐波增强。随后，利用该理论研究基于超表面的光子时间晶体，揭示了模态色散如何调控动量带隙的形成与动力学。这项工作为理解色散时变超表面及其潜在物理机制建立了一个综合平台。
英文摘要
Light-matter interaction in time-varying metasurfaces brings about phenomena that transcend the limits of static systems. Temporal modulation enables energy exchange between light and matter, and electromagnetic fields are coupled in both momentum and frequency, with implications across a broad range of photonic applications. Nevertheless, a precise description of such systems necessitates a theory that captures the intertwined effects of spatiotemporal variations while accounting for dispersion in a causal manner, as realistic optical materials exhibit frequency-dependent response and finite temporal memory. Here, a self-contained Floquet-Bloch theory is developed to capture the response of dispersive, time-varying metasurfaces, respecting causality through physically consistent constitutive relations. The theory treats spatial periodicity, nonadiabatic temporal modulation, and material dispersion within a unified formalism, providing access not only to the metasurface's scattering response but also to its inherent modal structure. The formulation is validated against full-wave simulations. As illustrative examples, it is first applied to asymmetric Floquet harmonic generation in an excitonic time-varying metasurface, where excitonic dispersion enables selective harmonic enhancement. It is then used to investigate metasurface-based photonic time crystals, revealing how modal dispersion governs momentum-bandgap formation and dynamics. This work establishes a comprehensive platform for understanding dispersive, time-varying metasurfaces and their underlying physical mechanisms.
