Deep and shallow trap contributions to the ionic current in the thermal-electric field poling in soda-lime glasses.

In this paper, we investigate the contribution of deep and shallow trapped ions on the second-order nonlinearity during typical poling procedures in soda-lime glass. The zero-electric field potential barriers of each contribution were estimated. The shallow traps, measured through the electrical ionic current, was determined as ~0.34 eV; while deep trap activation energy, measured by means of the thermal/electric field activated luminescence, was estimated ~3.8 eV. The traps show different dependence on its thermal energy onset for different applied electric field. The ionic current is linearly dependent on the electric field. The luminescence has a minimum electric field ~3.6 kV/cm and thermal energy ~31 meV (~87 degrees C) to occur. The average ionic jump lengths for both processes are also estimated, and the deep trap length is about ten times shorter than the shallow trap one. Samples poled at the border of the luminescence onset parameters revealed that the higher its contributions the more stable the induced second order nonlinearity.