Giant fluctuations of the intensities of local optical fields in fractal clusters are established, dependent on a high Q factor (low dissipation) of an optical resonance. We have shown that the nonlinear-optical enhancement by fractals is due to these fluctuations and not to a high mean magnitude of the local field. We have calculated the distribution function P(G) of a relative local-field intensity G and found a new scaling dependence, P(G)∝${\mathit{G}}^{\mathrm{-}\mathrm{\varepsilon }}$, with the index ɛ independent of an excitation frequency and dissipation rate.

• Received 30 April 1993

DOI:https://doi.org/10.1103/PhysRevLett.72.2486