Enhancement of excitonic absorption in WS₂ mediated by Huygens Si metasurfaces

Excitons in two-dimensional (2D) transition metal dichalcogenides are essential in optical responses. However, the absorption intensity remains limited at room temperature. This study presents a Huygens Si metasurface (MS) platform to enhance WS₂ excitonic absorption via coherent coupling and degenerate critical coupling (DCC), achieving near-unity total absorption up to 0.90. Different Mie modes contributed to this enhancement, originating from distinct physical effects. Notably, we demonstrated Miexcitons and observed an anticrossing phenomenon between the excitons and electric dipole (ED) mode induced by the coherent coupling. The intensity of the coherent coupling was significantly amplified by the DCC, resulting in an 18-fold increase in WS₂ absorption compared to that on a Si substrate. This platform provides a promising approach for advancing light-exciton interactions and the development of optical devices using 2D semiconductors.