Effective nonlinear optical properties of shape distributed composite media
CCAST (World Laboratory), PO Box 8730, Beijing 100080, PR China
2 Department of Physics, Suzhou University, Suzhou 215006, PR China
Corresponding author: a email@example.com
Published online: 4 June 2003
The effective linear and nonlinear optical properties of metal/dielectric composite media, in which ellipsoidal metal inclusions are distributed in shape, are investigated. The shape distribution function is assumed to be , where is the Heaviside function, Δ is the shape variance and Li are the depolarization factors of the ellipsoidal inclusions along i-symmetric axes (i=x,y). Within the spectral representation, we adopt Maxwell-Garnett type approximation to study the effect of shape variance Δ on the effective nonlinear optical properties. Numerical results show that both the effective linear optical absorption and the modulus of the effective third-order optical nonlinearity enhancement exhibit the nonmonotonic behavior with Δ. Moreover, with increasing Δ, the optical absorption and the nonlinearity enhancement bands become broad, accompanied with the decrease of their peaks. The adjustment of Δ from 0 to 1 allows us to examine the crossover behavior from no separation to large separation between optical absorption and nonlinearity enhancement peaks. As , i.e., the ellipsoidal shape deviates slightly from the spherical one, the dependence of on Δ becomes strong first and then weak with increasing the imaginary part of inclusions' dielectric constant. In the dilute limit, the exact formula for the effective optical nonlinearity is derived, and the present approximation characterizes the exact results better than old mean field one does.
PACS: 42.65.-k – Nonlinear optics / 82.70.Dd – Colloids / 81.05.Rm – Porous materials; granular materials / 72.20.Ht – High-field and nonlinear effects
© EDP Sciences, Società Italiana di Fisica, Springer-Verlag, 2003