Optical nonlinearity enhancement via geometric anisotropy

We investigate the effects of geometric anisotropy on the optical nonlinearity of metal nanocrystals in a dielectric host. By invoking the effective medium approximation for anisotropic composite media, we calculate the spectral density as a function of volume fraction and anisotropy. The results show that anisotropy not only changes the spectral function substantially and thereby has a pronounced effect on the nonlinearity, but also separates the absorption peak from the nonlinearity enhancement peak so that the figure of merit may be increased by orders of magnitude. We propose the use of electrorheological effect (e.g., during annealing) to realize these gains in optical nonlinearity.