Unveiling the Influence of Line Shape of Surface Plasmon Resonances on Exciton–Plasmon Strong Coupling

Strong coupling between surface plasmon resonance (SPR) modes and excitons holds great potential for many chemical and physical applications. However, a clear understanding on how far‐field spectral characteristics of SPR (linewidths and intensity) affect the coupling strength remains unclear because these parameters are difficult to be individually tuned. These spectral characteristics are associated with the damping rate and field enhancement that depend on the morphology of the plasmonic nanostructure. In this work, the influence of the SPR line shape on exciton‐plasmon coupling is systematically investigated by delicately tuning the linewidths and resonance intensities of the plasmonic arrays. It is found that the SPR modes with narrow linewidths or large intensity are favorable for the exciton–plasmon system to achieve strong coupling. The obtained clear relationships between the SPR line shape and coupling strength provide guidance for the design and optimization of exciton‐plasmon coupling systems, favoring the highly efficient manipulation of exciton polaritons and enabling specific applications driven by strong coupling. The influence of the spectral line shape of the plasmonic cavities on strong coupling is deeply explored thanks to the finely modulation of the damping rate (γp) and resonance strength (R). The near‐field properties can be reflected accurately and intuitively by spectral line shape, providing an effective and intuitive method for strong coupling optimization and prospective applications.