Fig. 1: Ag ND–WS₂ plexcitonic system and its steady-state/ultrafast optical properties.

a Schematic illustration of the Ag ND–WS₂ hybrid system, in which time-resolved pump–probe microscopy was adopted to study its ultrafast optical responses. b Normalized extinction spectra of the Ag ND–WS₂ hybrid system with increasing disk diameter (from bottom to top) in the range of 80–140 nm, with an increment of ~10 nm. The red and blue dashed lines represent the UB and LB of plexcitons, respectively, and the black dashed line indicates the exciton resonance location. c Time-resolved reflection spectra scan of the zero-detuning (disk diameter of 110 nm) Ag ND–WS₂ plexcitonic system under 2.0 eV pump excitation conditions at an incident fluence of 5 µJ cm⁻². The inserted white dashed line indicates the peak energy evolution of UB and LB plexcitons as a function of time. d Reflection spectra of the Ag ND–WS₂ plexcitonic system projected from the cross-section of (c) at t = 100 fs. From bottom to top, the incident fluence increases from 0.2 µJ cm⁻² to 12.5 µJ cm⁻². The grey dashed line is the probe reflection spectrum at −1 ps, which is unaffected by the pump pulse