Xia Meng, Chen Yuhua, Zhou Jiaxin, Wang Yuefeng, Huang Di, Zhang Xingwang
Suzhou Institute of Nano-Tech and Nano-Bionics (SINANO), Chinese Academy of Sciences (CAS), Suzhou, Jiangsu, 215123, P. R. China.
School of Nano-Tech and Nano-Bionics, University of Science and Technology of China, Hefei, Anhui, 230026, P. R. China.
Adv Mater. 2024 Sep;36(36):e2400214. doi: 10.1002/adma.202400214. Epub 2024 Jul 26.
Owing to their strong exciton effects and valley polarization properties, monolayer transition-metal dichalcogenides (1L TMDs) have unfolded the prospects of spin-polarized light-emitting devices. However, the wavefront control of exciton emission, which is critical to generate structured optical fields, remains elusive. In this work, the experimental demonstration of spin-locked vortex emission from monolayer Tungsten Disulfide (1L WS) integrated with Silicon Nitride (SiN) PhC slabs is presented. The symmetry-protected bound states in the continuum (BIC) in the SiN PhC slabs engender azimuthal polarization field distribution in the momentum space with a topological singularity in the center of the Brillouin zone, which imposes the resonantly enhanced WS exciton emission with a spin-correlated spiral phase front by taking advantage of the winding topologies of resonances with the assistance of geometric phase scheme. As a result, exciton emission from 1L WS exhibits helical wavefront and doughnut-shaped intensity beam profile in the momentum space with topological charges locked to the spins of light. This strategy on spin-dependent excitonic vortex emission may offer the unparalleled capability of valley-polarized structured light generation for 1L TMDs.
由于其强大的激子效应和谷极化特性，单层过渡金属二卤化物（1L TMDs）展现出了自旋极化发光器件的前景。然而，激子发射的波前控制对于产生结构化光场至关重要，目前仍然难以实现。在这项工作中，展示了与氮化硅（SiN）光子晶体平板集成的单层二硫化钨（1L WS）的自旋锁定涡旋发射的实验演示。SiN光子晶体平板中的连续统中对称保护的束缚态（BIC）在动量空间中产生方位角极化场分布，在布里渊区中心具有拓扑奇点，通过借助几何相位方案利用共振的缠绕拓扑结构，这使得具有自旋相关螺旋相位前沿的WS激子发射得到共振增强。结果，1L WS的激子发射在动量空间中呈现螺旋波前和甜甜圈形状的强度光束轮廓，拓扑电荷锁定到光的自旋。这种基于自旋相关激子涡旋发射的策略可能为1L TMDs提供无与伦比的谷极化结构化光产生能力。
