Propagation of exciton polaritons in a 1D photonic crystal-WS2 system

Exciton–polaritons (EPs) formed by strong coupling between excitons and optical modes combine the advantages of photons and excitons, providing a promising platform for applications in quantum information processing, quantum communication, and quantum transport. Using the transfer matrix method, finite-element simulations, and a coupled harmonic oscillator model, we investigate the strong coupling between bloch surface waves (BSWs) of 1D photonic crystals and excitons of WS2. The reflectance spectrum, Hopfield coefficients, entanglement entropy, group velocity, and propagation length of the EPs are calculated. At resonance, the hybrid system reaches maximum entanglement entropy, corresponding to a maximally hybridized exciton–photon state with equal excitonic and photonic contributions. The group velocity of EPs in the photonic-like regime is significantly large, greatly beyond the bare exciton transport. By introducing the lifetime ratio of the exciton to the BSW mode, we identify three distinct regimes of propagation length, which, respectively, favor high-speed interconnects, coherent synergy, or strong nonlinearity. This study provides a framework for understanding BSW-exciton polaritons and offers design guidelines for high-performance polaritonic devices.