光子晶体中能谷调控光传输的理论与实验研究

In this project, we will theoretically and experimentally study the valley controlled light propagation in photonic crystals by exploiting the valley degree of freedom. We will demonstrate the coupling mechanism between valley, orbital and pseudo-spin degrees of freedom by studying various kinds of photonic crystals with different structures or materials. A set of topological invariants will be employed to characterize the topological distinction between topological phases. The classification of topological phases in photonic crystals will be illustrated and the valley-polarized topological phase with non-zero valley Chern number will be put forward. Based on this novel topological phase, optical two-dimensional or quasi three-dimensional slab structures will be designed and the valley-protected scattering-immune transport of will be studied. It will pave a new way for the design of low-loss photonic integrated devices. In addition, spin or orbital angular momentum based vortex optical fields will be used to manipulate valley bulk or edge states, far-field transmission spectra and near-field electromagnetic field scanning will be used to detect the transport of valley states. Photonic valley Hall effect and its induced beam splitting, which provide a new route to light manipulation in nanostructures, will be also studied. Through the project, we aim to unveil some novel physics, phenomena and effect in valley photonics, realize high efficient light propagation and optical manipulation by employing the valley degree of freedom, and also lay a theoretical foundation for the design of photonic devices such as the low-loss photonic integrated waveguides and photonic splitters.

本项目拟从物理机制和实验探索两方面，以能谷自由度为切入点，重点研究光子晶体中的能谷调控光传输行为。拟通过设计不同空间构型和材料成分的光子晶体，揭示能谷与轨道、赝自旋等內禀自由度的耦合机制，建立完备的拓扑不变量数组，阐明光子晶体中不同拓扑相的区别与联系，实现拓扑相分类并发现能谷陈数非零的新型能谷拓扑相。拟基于新型能谷拓扑相，设计结构简单的光学二维/准三维波导结构，研究能谷保护抗散射传输行为，为开发低损耗光子集成器件提供设计思路。拟结合自旋/轨道角动量等结构光场实现对能谷态的调控，结合远场谱线测量与近场探测表征能谷态的传输，研究光能谷霍尔效应及其诱导光束分离，为微纳结构中光场调控提供新思路和新途径。我们期待通过本项目的实施，揭示若干能谷相关的新物理、新现象、新效应，以能谷为新型自由度实现高效光传输和结构光场调控，为低损耗光子集成波导、光分束器等器件开发提供理论基础。

光具有传输频带宽、传输速度快、传输载量大等优点，人们希望实现精准光场调控，使光成为下一代信息载体。本项目以能谷自由度为切入点，从物理机制和实验探索两方面研究光子晶体中的能谷调控光传输行为。按照执行计划，本项目顺利完成了项目全部研究内容，实现了全部研究目标：1）利用完美电导体上光子晶体阵列实现了二阶拓扑相、利用各向异性非磁性光子晶体实现了自旋霍尔拓扑相、利用频率自由度实现了频段依赖能谷拓扑相，实现了光子晶体的拓扑相分类和挖掘了新型能谷拓扑相。2）在绝缘层硅上制备出能谷光子晶体平板，证实了近红外波段下能谷保护的宽带抗散射传输。提出了硅基叠层拓扑光子晶体波导，获得了两种拓扑保护边界态。3）实现了光束偏转、自旋偏振光单向传输、频率依赖光学能谷霍尔效应等新型光传输行为，证实了光子晶体中的能谷霍尔效应及其光束分离方面的应用前景。系列光子晶体成果深入研究了光子晶体中的能谷调控光传输行为的新现象，为光场调控带来了新途径和新思路，丰富了拓扑光子学的研究内容，也为片上集成光波导、片上微腔、波分解复用器、光分束器等新型光子器件设计提供了新原理和新方法。.项目执行期内，标注资助的研究论文无论在质量和数量两方面都超过预期目标，发表SCI论文12篇，含Physical Review Letters、Nature Communications、Laser & Photonics Reviews、Physical Review Applied等5篇代表性论文。PRL的局域角态工作陆续被国内外研究小组在其他体系证实，Nat. Commun.的硅基波导抗散射光传输实验方案被多个国外光学实验小组采纳。受邀完成了3个邀请报告，并在多个会议上作口头报告。此外，项目负责人陈晓东副教授获广东省杰出青年基金资助（2019），目前在读硕士生2名。