Boosting Strong Coupling in a Hybrid WSe₂Monolayer-Anapole-Plasmon System

The exciton-polaritonic states are generated by the strong interaction between photons and excitons in confined nanocavities. To achieve strong coupling between excitons in TMDCs and optical modes in cavities is quite challenging due to fabrication issues, modal and material dispersion in the cavity, and the weak confinement of the optical field. Hence, investigation of new photonic structures to achieve strong coupling in TMDCs materials is necessary to develop polariton-based devices. Here, we report the observation of the strong coupling between an anapole mode in a slotted silicon nanodisk and an exciton in a WSe2 monolayer, leading to the creation of anapole-exciton polaritons. Furthermore, we have also demonstrated a strong anapole-plasmon and anapole-plasmon-exciton coupling in Si-Ag, and Si-Ag-WSe2 heterostructures, respectively. The observed polaritonic hybrid states have a large Rabi splitting (159 meV) accompanied by high localized field enhancement (157 times increase) in the near field and at a normal incident angle, suggesting a crucial step toward the creation of exciton-polariton nanodevices.