Anderson localization of surface plasmons and nonlinear optics of metal-dielectric composites

A scaling theory of local-field fluctuations and optical nonlinearities is developed for random metal-dielectric composites near a percolation thresho ld. The theory predicts that in the optical and infrared spectral ranges th e local fields are very inhomogeneous and consist of sharp peaks representi ng localized surface plasmons. The localization maps the Anderson localizat ion problem described by the random Hamiltonian with both on- and off-diago nal disorder. The local fields exceed the applied field by several orders o f magnitudes resulting in giant enhancements of various optical phenomena. The developed theory quantitatively describes enhancement in percolation co mposites for arbitrary nonlinear optical process. It is shown that enhancem ent strongly depends on whether a nonlinear multiphoton scattering includes the act of photon subtraction (annihilation). The magnitudes and spectral dependencies of enhancements in optical processes with photon subtraction, such as Raman and hyper-Raman scattering, Kerr refraction, and four-wave mi xing, are dramatically different from those in processes without photon sub traction, such as in sum-frequency and high-harmonic generation. At percola tion, a dip in dependence of optical processes on the metal concentration i s predicted. [S0163-1829(99)15547-4].