Figure 4.

Experimentally measured interferometric autocorrelation traces of the photoemission from a single nanosponge and the simulation based on a phenomenological localization model. The data (filled circles) are taken from nanosponges A (a) and B (b) and are compared to the model simulations (solid line). In the insets, the measurements and simulations are shown on a logarithmic intensity scale. In the simulation, the response of nanosponge A is taken as the sum of a short-lived, delocalized, dipolar plasmon mode (field decay time τ_P=5 fs; nanosponge B: τ_P=3 fs) and seven (nanosponge B: nine) localized, long-lived plasmon modes with decay times of τ_H=50 fs (nanosponge B: τ_H=40 fs). In the simulation, a fifth-order optical nonlinearity is assumed.