Large second-harmonic signal in thermally poled lead glass-silica waveguides

Thermal poling of silica-lead glass-silica waveguides formed by laser ablation of lead glass and e-beam evaporation of the silica cladding is reported. A large nonlinearity localized within the Pb-glass layer was found by scanning the probe laser beam across an angle-polished sample, and a peak second-order nonlinear susceptibility ${\chi }^{\text{(2)}}$ as high as 15 pm/V was achieved in the Pb-glass layer. A simple theoretical model based on charge transport in the different materials during poling is proposed to explain complex ${\chi }^{\text{(2)}}$ profile. The large third-order nonlinearity of lead glass plays a key role in the generation of the large second-harmonic signal.