Buried waveguide in neodymium-doped phosphate glass obtained by femtosecond laser writing using a double line approach

We fabricate a buried channel waveguide in neodymium-doped phosphate glass using a double line approach by femtosecond laser writing. Raman spectra reveal an expansion of the glass network in the laser irradiated region. Given the stress-induced positive refractive index change, waveguiding between two separated tracks is demonstrated. The refractive index difference profile of the waveguide is reconstructed from the measured near-field mode. Propagation loss is measured by scattering technique. Microluminescence spectra reveal that the Nd 3+ fluorescence property is not significantly affected by waveguide formation process, which indicates that the inscribed waveguide is a good candidate for active device.