Crystallization effect on non-linear optical response of silicate glass and glass-ceramics containing gold nanoparticles

Silicate glasses and glass-ceramics containing gold nanoparticles have been prepared by a conventional melt-quenching method and the subsequent two-st ep heat treatment processes. The relaxation time of non-linear optical resp onse of the gold nanoparticles has been evaluated from femtosecond pump-pro be measurements. The gold nanoparticles are precipitated through a heat tre atment. A second heat treatment leads to the precipitation of Li2SiO3 nanoc rystals on the gold nanoparticles. The relaxation of non-linear optical res ponse consists of two components; one is a fast relaxation within a few pic oseconds, which originates from an electron-phonon coupling process, and th e other is a slow relaxation due to a thermal diffusion of excess heat from nanoparticles to the glass matrix. Crystallization does not affect the rel axation of the fast component, while the relaxation time of the slow compon ent decreases with an increase in the degree of crystallinity. We propose t hat the increased thermal conductivity in precipitated crystals, i.e., Li2S iO3 nanocrystals, leads to the increase in the speed of the relaxation proc ess which works by thermal diffusion from metal particles to the matrix. (C ) 2001 Elsevier Science B.V. All rights reserved.