Large third-order nonlinear refractive index coefficient based on gold nanoparticle aggregate films

Abstract

Au nanoparticles show large third-order nonlinear effect and ultra-fast response. Here a high nonlinear aggregate film based on self-assembled gold nanoparticles is reported and its third-order nonlinear refractive index coefficient is measured by Z-scan experiment. The third-order nonlinear refractive index coefficient of the Au nanoparticle aggregate film (γ1 = 9.2 × 10−9 cm2/W) is found to be larger than that of an 8-nm-thick sputtered Au film (γ2 = 6.5 × 10−9 cm2/W). This large nonlinear effect can be attributed to the strong field enhancement due to localized plasmon resonances between Au nanoparticles. The result shows that the self-assembled Au nanoparticle aggregate film could be a promising candidate as a third-order nonlinear optical material.