Strong coupling in metal-WS₂ hybrid system

Metallic particle array as an effective plasmonic cavity has attracted great interest. Coupling between such plasmonic cavity and gain materials have been reported. In this work, we studied two kinds of polaritons in such system. First, we studied the strong coupling between groove localized surface plasmon resonance (LSPR) and lattice surface plasmon polariton in a metallic groove array. We found that the optical response of such system is different from the ordinary weak coupling surface lattice resonance. A giant Rabi splitting of ~440 meV was observed, both angle and pitch tuning. The underlying mechanism is analyzed. Next, we studied the coupling between the metallic grating and the exciton in WS₂ monolayer. LSPR was used. The parallel electric field within the groove can provide an effective coupling to the excitons of monolayer WS₂. To overcome the problem of angle tuning reported in previous work, we developed a depth chirped grating to realize the resonance tuning. A moderate Rabi splitting of 56 meV was observed. These works demonstrate the potential application in strong coupling devices based on plasmonic cavity.