The build-up time of the thermal lens effect induced by a Gaussian beam in
the DO3-doped sol-gel system xTiO(2).(100 - x)SiO2 at different composition
s, both in the liquid and gel phases has been measured in a Z-scan geometry
. While the pure titania samples show a minimum of the thermal diffusivity,
a maximum is found for x approximate to 30. The sol to gel transformation
leads to an increase of the build-up times at all compositions. (C) 1999 El
sevier Science B.V. All rights reserved.