Fig. 1. Spectral distribution of the LSP resonances in a plasmonic sphere.

Fig. 2. Polarization charge density of the first few resonant modes of a plasmonic sphere.

Fig. 3. (a) Time evolution of the position X of a harmonic oscillator in a parabolic potential U. (b)–(d) Time evolution of a parametrically driven oscillator with time-varying potential. (b) Below threshold, the oscillation decays. (c) At the threshold of parametric regeneration, the dissipations are exactly compensated. (d) Above threshold, the parametric gain causes the oscillations to grow exponentially.

Fig. 4. Polarization density amplitude term P11,0(e) of a silver sphere immersed in an MNA background medium. In order to better highlight the relaxation oscillations occurring in the system, we show a case in which the PPR threshold is exceeded by a large margin (Ap=20APPR). The dashed lines show the oscillation limits predicted by the asymptotic Eq. (12).

Fig. 5. Absorption cross-section of the plasmonic particle normalized to the geometrical cross-section as a function of the incident intensity.

Fig. 6. Orange curve shows the instantaneous pump power Winc. The blue curve shows the instantaneous pump power Wabs absorbed by the particle via PPR of the n=11, m=0 mode. The dashed vertical lines indicate the times at which the pump intensity is equal to the PPR threshold.