Effective nonlinear optical properties and optical bistability in composite media containing spherical particles with different sizes

We study the effective nonlinear optical properties of composite media in which identical nonlinear nanospheres are randomly embedded in the linear host medium. In the weakly-nonlinear case, we aim at the effective linear permittivity and effective third-order nonlinear susceptibility with effective medium theory combined with the linear Mie theory. We show that large enhancement of optical nonlinear susceptibility can be achieved at the surface plasmon resonant wavelength, which can be tuned by changing the size of nanoparticles. Our numerical results are compared with those in the quasistatic limit or/and from Comsol simulations, good agreement is found. In the strong-nonlinear case, based on nonlinear Mie theory and self-consistent mean-field method, we study the optical bistability of the composite media. The optical bistability and tristability are found, and the bistable threshold fields are found to be strongly dependent on the sizes of nanoparticles and the incident wavelength. Such nonlinear nanocomposites with large optical nonlinearity and tunable bistable behavior are envisioned for use as nonlinear optical nanodevices such as optical nanoswitches, optical nanomemories and so on. (C) 2016 Optical Society of America