Fig. 4. Electron transition dynamics.

(A) Picosecond transient absorption spectra of the gain material without plasmon cavity. (B) Evolution of transient absorptive signature of S₁→S_n (470 nm, τ = 21.5 ps) and T₂→T_n (570 nm, τ = 25.3 ps) along with time, corresponding to a fast intersystem crossing. (C) Decay of transient absorption at 430 nm represents nonradiative relaxation of SiO₂ (τ = 6.8 ps). The dip of about 490 to 530 nm could be attributed to the overlap of ground-state absorption and fluorescence emission. OD, optical density.