We demonstrate that electric-field-assisted ion-exchange in glass allows one to obtain a structure with close to a step-like concentration and conductivity profiles. Application of DC voltage to the ion-exchanged glass results in charge accumulation. The electric field induces symmetry breaking and provides quadratic optical susceptibility in the glass. Nonlinear optical properties of modified glass are studied using the Maker fringe technique. Particularly, we study the influence of the nonlinear susceptibility tensor components ratio \(χ_{zxx} : χ_{zzz} \) on resulting characteristics. Comparing modeling and experiments, we deduced the ratio 1:3 which corresponds to Kleinman symmetry of isotropic materials.