Optical second harmonic generation in poled MgO-ZnO-TeO2 and B2O3-TeO2 glasses

Optical second harmonic generation has been observed in electrically poled MgO-ZnO-TeO2 and B2O3-TeO2 glasses. The theoretical Maker fringe curve fitted to the experimental data leads to the fact that the poled region is almost identical with the sample thickness. In other words, the poled region is not restricted to the surface of the sample. For the MgO-ZnO-TeO2 glasses, the second harmonic intensity is higher in the glass with lower glass transition temperature when the poling temperature is constant. It is thought that the orientation of asymmetrical tellurite structural units which possess electric dipole moments causes the optical second harmonic generation and that the orientation takes place as a result of the structural relaxation of the tellurite network around the glass transition temperature. The second harmonic intensity and the second-order non-linear coefficient are larger for the MgO-ZnO-TeO2 glasses than for the B2O3-TeO2 glasses. This phenomenon is explainable in terms of the difference in the glass network structure between these two systems.