Wen Xinglin, Zhou Yunxi, Chen Sijie, Yao Wendian, Li Dehui
School of Optical and Electronic Information, Huazhong University of Science and Technology, Wuhan 430074, China.
Wuhan National Laboratory for Optoelectronics, Optical Valley Laboratory, Huazhong University of Science and Technology, Wuhan 430074, China.
Nanophotonics. 2023 Aug 1;12(17):3529-3534. doi: 10.1515/nanoph-2023-0368. eCollection 2023 Aug.
Due to the short valley polarization time, it is hardly to separate opposite valley pseudospin of transition metal dichalcogenides (TMDs) for their practical applications in valleytronics. Coupling TMDs to unidirectional surface plasmon polariton (SPP) can overcome this obstacle. However, it is required to break the symmetry to induce the asymmetric coupling between valley exciton dipole and SPP to route valley exciton in previously proposed strategies. Herein, by utilizing a new mechanism that near-field interference can create directional SPP in symmetric nanostructures, we realize directional routing of valley exciton emission of monolayer WSe at room temperature with a symmetric nano-slits array. The near-field interference enabled directional SPP in our device not only render the exciton diffusion length increase from 0.9 to 3.0 μm, but also lead to a valley exciton separation length of 0.7 μm with degree of valley polarization up to 22 %. This valley excitons separation is attributed to the non-flat WSe in the nano-slits region, which makes the exciton dipoles present in-plane and out-of-plane simultaneously. Our work provides a convenient and promising strategy towards room temperature on-chip integrated valleytronic devices.
由于谷极化时间短，在谷电子学的实际应用中，很难分离过渡金属二硫属化物（TMDs）的相反谷赝自旋。将TMDs与单向表面等离激元极化激元（SPP）耦合可以克服这一障碍。然而，在先前提出的策略中，需要打破对称性以诱导谷激子偶极子与SPP之间的不对称耦合，从而引导谷激子。在此，通过利用一种新机制，即近场干涉可以在对称纳米结构中产生定向SPP，我们在室温下利用对称纳米狭缝阵列实现了单层WSe谷激子发射的定向路由。我们器件中由近场干涉实现的定向SPP不仅使激子扩散长度从0.9增加到3.0μm，而且导致谷激子分离长度为0.7μm，谷极化程度高达22%。这种谷激子分离归因于纳米狭缝区域中不平坦的WSe，这使得激子偶极子同时呈现面内和面外状态。我们的工作为室温片上集成谷电子器件提供了一种便捷且有前景的策略。
