Static and dynamic profile of the electric field within the bulk of fused silica glass during and after thermal poling

We use the electric-field-induced second-harmonic (EFISH) technique to characterize, for the first time to our knowledge, the profile of the electric field induced within the bulk of fused silica glass samples both during and after thermal-poling treatment. During thermal poling, the initially homogeneous electric field decays exponentially from the anodic to the cathodic surface. After the poling treatment, a permanent electric field is induced within the bulk of the sample. It also decays exponentially from a positive value on the anodic surface to a negative value on the cathodic surface. The exponential decay constant depends on the thickness of the sample, the poling time, and the temperature. The temperature evolution of this constant makes it possible to retrieve the activation energy of the rapidly moving ionic species. This ensemble of observations indicates that modifications to models previously proposed are necessary.