Figure 5. Time evolution of the dipolar moment of the nanoparticle p₁(t) of a 10-nm silver nanoparticle.

The nanoparticle is under constant excitation from the probe field E₀, while the pump is switched on from t = 0 on. (a) Example of stable regime (amplifying regime, under spasing threshold). (b) Example of onset of the spasing regime (above threshold).