多波段拓扑群速度控制：从慢光到光存储
Long-range coupling enabled multiband group-velocity control of topological edge states from slow light to light stopping
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中文总结 AI 辅助
研究通过将NNN耦合引入光子晶格建立拓扑光子平台，实现群速度工程。利用NNN耦合打开带隙、平坦边缘态色散，实现拓扑慢光控制及多波段拓扑光存储，为相关光电器件提供新设计原则。
中文摘要 AI 辅助
我们将次近邻（NNN）耦合引入哈珀 - 霍夫施塔特光子晶格，以建立用于群速度工程的长程拓扑光子平台。NNN耦合不仅打开了先前封闭的带隙，还使边缘态色散平坦，为拓扑慢光控制提供了潜在途径。理论计算表明带隙支持具有相反符号的带隙陈数。传播模拟证明了反手性边缘态的稳健、拓扑保护的慢光传输，且所有三个拓扑带隙中慢光边缘态的存在实现了宽带拓扑慢光。通过进一步调整NNN耦合参数，可实现多个拓扑光存储状态。这些结果确立了长程NNN耦合作为拓扑群速度工程的有效机制，并为拓扑慢光器件、光学延迟线和集成多波段光子系统提供了新的设计原则。
英文摘要
Topological edge states provide robust optical transport immune to disorder, yet their propagation velocity is usually constrained by the intrinsic band dispersion, limiting dynamic control of topological light transport. We introduce long-range next-nearest-neighbor (NNN) couplings into a Harper--Hofstadter photonic lattice and establish a versatile platform for group-velocity engineering. We demonstrate that the NNN couplings play two distinct roles: the vertical coupling opens a previously closed topological band gap by lifting the degeneracy of bulk bands, while the horizontal coupling reshapes the edge-state dispersion through momentum-dependent corrections, enabling controllable topological slow-light transport. Furthermore, the band-gap Chern numbers associated with different gaps exhibit opposite signs, giving rise to topological edge states with opposite chiralities. Propagation simulations reveal robust unidirectional transport of these counter-chiral edge states with reduced group velocities. By continuously tuning the NNN coupling strength, the group velocity of topological edge modes can be reduced toward zero at specific momenta, resulting in topological light-stopping effects. These results demonstrate that long-range NNN couplings provide an effective mechanism for engineering momentum-dependent topological group velocities and offer new possibilities for robust slow-light devices, optical delay lines, and multiband integrated photonic systems.
