Effect of core-cladding interface on thermal poling of germano-silicate optical waveguides

We report on the effect of the interface between silica and germano-silicat e glass during thermal poling of optical waveguides. By measuring the depth of the nonlinear region, using the Maker's fringes technique combined with etching in hydrofluoric acid, we conclude that the germania-doped layer ac ts as a barrier for the migration of cations at standard poling temperature and voltage. It is also found that the problem can be circumvented by poli ng at higher temperature and voltage, e.g. 320 degreesC and 8 kV. (C) 2001 Published by Elsevier Science B.V.