Size-dependent optical nonlinearity of Au nanocrystals

Abstract

Gold nanoparticles of different sizes are prepared by laser ablation of the gold target in deionized water. The UV/visible absorption spectra show surface plasmon resonance bands that are redshifted in wavelength with an increase in particle size. An increase in particle size is observed with increasing laser pulse energy. The optical absorptive nonlinearity of the nanoclusters shows an optical-limiting-type nonlinearity, which finds application in the fabrication of optical-limiting devices. The limiting efficiency decreases with an increase in particle size. The Au nanoparticle shows good nonlinear refraction, which is of a self-defocusing nature. Both the real and imaginary parts of nonlinear susceptibility increase with a decrease in particle size. A stable nonlinear device is fabricated by incorporating Au nanocrystals in a polymer matrix.