Effective nonlinear optical properties of metal-dielectric composite media with shape distribution

The effective linear and nonlinear optical properties have been investigated in granular metal-dielectric composites taking the geometric shape of inclusions into account. Recently derived Maxwell-Garnett-type approximations are generalized to study the spectral function for composites in which the metal inclusions have a uniform distribution of geometric shapes. The numerical results show that the spectral density function becomes a prominent peak around small spectral value s within the non-self-consistent Maxwell-Garnett approximation but a broad continuous spectrum around large s besides the prominent peak around small s within the self-consistent Maxwell-Garnett approximation. Based on the spectral representation, we investigate the optical absorption and third-order nonlinear optical susceptibility. The results indicate that the shape distribution can lead to the separation of the nonlinearity enhancement peak from the absorption peak and thereby make the figure of merit more attractive.