Evidence of space-charge effects in thermal poling

The in situ thermal poling processes in germanosilicate fibers for positive and negative poling voltages are significantly different. Thermal poling o f silica fibers consists of two processes: the faster linear process of cha rge migration and the subsequent single exponential process of charge ioniz ation. Both the shielding electrical field due to charge migration and the ionization electrical field due to charge ionization are able to be frozen- in at room temperature acid lead to the residual linear electrooptic effect s, The observations support that the mechanism of the induced electrooptic effects is based on space charge electrical fields instead of dipole/bond o rientation.