光子时间晶体中的动态手性
Dynamic Chirality in Photonic Time Crystals
- City University of Hong Kong（香港城市大学）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
提出时空光子时间晶体，通过方位角行波介电调制实现合成旋转，解除模态简并产生手性模式，实现可调圆二色性，为无机械运动可重构手性光子学提供新策略。
AI中文摘要：
时间调制为主动波控制提供了一种根本不同的自由度，超越了静态空间结构。光子时间晶体（PTCs）基于电磁参数在时间上的周期性调制，通过实现光与调制之间的可控能量交换，将光子带工程从空间扩展到时间。然而，利用PTCs来合成旋转动力学从而控制手性和圆二色性（CD）仍 largely 未被探索。在此，我们提出一种时空PTC，其中心圆柱元件由方位角行波介电常数调制驱动。尽管结构在几何上是静态的，但其介电分布随时间演化为有效旋转的图案。这种合成旋转解除了一种静态模态简并，产生两个具有相反轨道角动量的非简并反向旋转态。这些手性模式选择性地耦合到左旋和右旋圆偏振光，产生可调谐的CD。此外，时空调制在Floquet复制带之间诱导轨道角动量转换。我们的工作揭示了动态手性响应的微观起源，并建立了一种无需机械运动即可实现可重构手性光子学的策略。
英文摘要：
Temporal modulation offers a fundamentally distinct degree of freedom for active wave control beyond static spatial structuring. Photonic time crystals (PTCs), based on periodic modulation of electromagnetic parameters in time, have expanded photonic band engineering from space to time by enabling controlled energy exchange between light and the modulation. Yet, the use of PTCs to synthesize rotational dynamics and thereby control chirality and circular dichroism (CD) remains largely unexplored. Here, we propose a spatiotemporal PTC whose central cylindrical element is driven by an azimuthally traveling-wave permittivity modulation. Although the structure is geometrically static, its dielectric profile evolves as an effectively rotating pattern in time. This synthetic rotation lifts a static modal degeneracy and produces two nondegenerate counter-rotating states with opposite orbital angular momenta. These chiral modes selectively couple to left- and right-circularly polarized light, giving rise to tunable CD. In addition, the spatiotemporal modulation induces orbital angular-momentum conversion between the Floquet replica bands. Our work reveals the microscopic origin of dynamic chiral response and establishes a strategy for reconfigurable chiral photonics without mechanical motion.
