Dynamics of the second-order nonlinearity in thermally poled silica glass

We study the temporal evolution of both the second-order nonlinear coeffici ent and of the nonlinear thickness in thermally poled silica-glass slides b y using a high-resolution all-optical technique. A time delay in the nonlin earity formation is observed, followed by an increase to a maximum, and a f inal decrease. The thickness is shown to increase at a rate that differs si gnificantly from that reported for the corresponding ionic charge fronts. O ur measurements also show strong dependencies on sample thickness and these can be attributed to different electric fields in the depletion region. (C ) 2001 American Institute of Physics.