Time evolution of depletion region in poled silica

The electric field recorded in silica samples thermally poled during various intervals was measured by etching. The field is nearly uniform and increases to a maximum (similar to3.6x10(8) V/m) in few minutes of poling and subsequently decreases slowly toward a steady level (similar to1.4x10(8) V/m). The depletion layer becomes neutral even before the field reaches steady state. An upper limit of (0.7+/-0.2) mum was found for the thickness of the negatively charged edge of the depletion region. The value of chi((3)) is the same for all poling times. (C) 2003 American Institute of Physics.