Quasibound states in continuum-induced double strong coupling in perovskite and WS2 monolayers

In recent years, the formation of exciton-polaritons in semiconductor materials has attracted major interest because of their exotic optical properties, allowing the study of many interesting physical phenomena, such as superfluids and Bose-Einstein condensation. Here, we demonstrate a double strong coupling regime in a perovskite and tungsten disulfide (WS2) monolayer using single and dual quasibound states in the continuum (QBIC). Except for supporting exciton resonance, bi(phenethylammonium)tetraiodoplumbate perovskite thin film is patterned as a grating to act as a single symmetry-protected bound state in the continuum (BIC) or dual BICs by harnessing its high index. A WS2 monolayer is sandwiched inside the perovskite nanowire so that a single BIC can be strongly coupled to both exciton resonances of perovskite and WS2 monolayers with a Rabi splitting of 380 and 42.2 meV. We found that the Q factor and thickness of perovskite film play a central role in governing the coupling strength. In addition, we demonstrate that double strong coupling can be satisfied by using dual QBICs, where each QBIC is individually coupled to the exciton of either a perovskite or a WS2 monolayer. The design approach achieves a Rabi splitting as high as 353.6 and 31.80 meV in the perovskite and the WS2 monolayer, respectively. This is a demonstration of a double strong coupling regime using a single structure based on perovskite and WS2 monolayers. The realization of double strong coupling paves the way for the emergence of polaritonic devices with advanced functionalities, such as dual wavelength polariton nanolasers.