2pm/V in Poled Bismuth-Zinc-Borate High Index Glass

Thermal poling freezes an intense static electric field (Edc) in glass resulting in a permanent second-order nonlinearity via a rectification process: χ
⁽²⁾
=3χ
⁽³⁾
E
dc
. The low third-order nonlinearity limits the χ
⁽²⁾
of silica glass to 0.7 pm/V. Hence, poling of high χ
⁽³⁾
glasses offers an attractive route towards glass based integrated electro-optical modulators and frequency converters for which χ
⁽²⁾
of the order of 5 pm/V or higher would be desirable. In the present work 2 pm/V have been demonstrated in poled bismuth-zinc-borate glass planar waveguides with opportunely chosen substrates having lower electrical resistance than the guiding region. The innovative sample configuration, which provided a 4-fold improvement in the induced χ
⁽²⁾
compared to bulk glasses [1], was suggested by a poling model that takes into account both ionic and electronic conduction. The χ
⁽²⁾
is found to be limited by the onset of nonlinear conductivity. This work opens the way to a further enhancement of χ
⁽²⁾
through tailoring the nonlinear conductivity via the glass composition and preparation.