Germanium-doped multi-layer waveguides containing a silicon oxy-nitride layer as a charge trapper are thermally poled in an air environment. Compared to the waveguides without the trapping layer, the induced linear electro-optic coefficient increases more than 20%. A comparable rise in the internal field is found. Our results demonstrate an optimization of the optical nonlinearity by shaping the built-in internal field with the charge-trapping layer.
Applied Physics B, 2004, Vol 78, Issue 3-4, p. 371-375