Molecular Polaritons Generated from Strong Coupling between CdSe Nanoplatelets and a Dielectric Optical Cavity

We demonstrate the formation of CdSe nanoplatelet (NPL) exciton-polaritons in a distributed bragg reflector (DBR) cavity. The molecule-cavity hybrid system is in the strong coupling regime with an 83 meV Rabi splitting, characterized from angle-resolved reflectance and photoluminescence measurements. Mixed quantum-classical dynamics simulations are used to investigate the polariton photo-physics of the hybrid system by treating the electronic and photonic degree of freedom (DOF) quantum mechanically, and the nuclear phononic DOF classically. Our numerical simulations of the angle-resolved photoluminescence (PL) agree excellently with the experimental data, providing a fundamental explanation of the asymmetric intensity distribution of the upper and lower polariton branches. Our results also provide mechanistic insights into the importance of phonon-assisted non-adiabatic transitions among polariton states which are reflected in the various features of the PL spectra. Our work proves the feasibility of coupling nanoplatelets into a dielectric cavity to form a hybrid system and provides a new platform for investigating cavity-mediated physical and chemical processes.