Transport and Spatial Separation of Valley Coherence via Few Layer WS2 Exciton–Polaritons

• Published in: ACS photonics Vol. 11; no. 3; pp. 1078 - 1084
• Main Authors: De-Eknamkul, Chawina, Huang, Wenzhuo, Zhang, Xingwang, Ren, Yundong, Cubukcu, Ertugrul
• Format: Journal Article
• Language: English
• Published: American Chemical Society 20.03.2024
• Subjects: atomically thin waveguide; guided-mode resonance; directional propagation; 2D materials; WS2
• ISSN: 2330-4022; 2330-4022
• DOI: 10.1021/acsphotonics.3c01484

The optical response in two-dimensional transition-metal dichalcogenides (2D TMDCs) is dominated by excitons. The lack of spatial inversion symmetry in the hexagonal lattice within each TMDC layer leads to valley-dependent excitonic emission of photoluminescence. Here, we demonstrate experimentally the spatial separation of valley coherent emission into orthogonal directions through self-resonant exciton polaritons of a free-standing three-layer (3L) WS2 waveguide. This was achieved by patterning a photonic crystal consisting of a square array of holes, allowing for the far-field probing of valley coherence of engendered exciton–polaritons. Furthermore, we report a detailed experimental modal characterization of this coupled system in good agreement with the theory. Momentum space measurements reveal a degree of valley coherence in the range 30–60%. This work provides a platform for the manipulation of valley excitons in coherent light–matter states for potential implementations of valley–coherent optoelectronics.