Fractals in microcavities: Giant coupled, multiplicative enhancement of optical responses

A novel class of optical materials, microcavities doped with nanostructured fractal aggregates, was studied. Fractal aggregate optical excitations may be concentrated in regions smaller than the diffraction limit of conventional optics, resulting in large local fields. Seeding the aggregates into microcavities further increases the local fields because of light trapping by microcavity resonance modes. These microcomposites possess unique optical properties, including very large probabilities of radiative processes. In our experiments, lasing at extremely low pump intensities, below 1 mW, and strongly enhanced Raman scattering was observed in fractal-microcavity-dye composites.