Ultrafast Nonlinear Optical Response in Multilayer Silica-Capped Gold Nanoparticle Films

摘要

Gold nanoparticles were prepared by NaBH_4 reduction method, and homogeneous SiO_2 were coated on gold nanoparticles and assembled into densely-packed 3-dimensional arrays by the layer-brayer self-assembly (LBL) technique. Every layer of films exhibited densely packed 2-dimensional arrays of Au@SiO_2 composite nanoparticles and the film thickness was controllable through the number of deposition cycles. These multilayer films exhibited high volume fraction of gold nanoparticles (0.047). The imaginary part of the third-order nonlinear optical susceptibility (Imx~(3)) with different deposition layer have been investigated by femtosecond pump and probe spectroscopy. The Imx~(3) value is about (-8.7±3.3)×10~(-11) esu and almost not dependent with the layer numbers which indicates every layer of our films has the same structural and optical properties.