Fractals: Localization of dipole excitations and giant optical polarizabilities

Highly localized optical modes laser-excited on silver colloid fractal clusters were observed using photon scanning tunnelling microscopy (PSTM). The spatial distribution of the modes excited shows the frequency and polarization selectivity suggested by numerical simulations. The localization of the optical excitations on fractals results in very high local fields leading to the huge enhancement of resonant Rayleigh, Raman and, especially, nonlinear light scattering. The experimental results verify the main concepts of the developed resonant optical theory of fractals.