Figure 2.

Spectral characterization of the nanosponges. Experimentally measured (full lines) and calculated (dark dashed lines) extinction spectra for nanosponges A (a) and B (b) from Figure 1. The incident field is polarized along the semi-minor axis of the ellipsoids. The spectra are normalized to the extinction maximum of nanosponge A. The narrower resonances on top of the fundamental dipole resonance are attributed to the coherent, resonant interaction of the dipole mode with the localized long-lived modes. Calculated scattering spectra (dark dashed lines) for the half-ellipsoidal nanosponges with the same overall dimensions are in good general agreement with the experimental data but underestimate the mode-coupling. Long-lived modes can, however, be seen in the calculated absorption spectra (light dashed lines, 10-fold enhanced).