The structural and refractive index changes in the waveguides written by femtosecond laser in Er-doped silicate glasses

Waveguides with low propagation losses were written in erbium-doped silicate glasses by tightly focused femtosecond laser pulses. Raman spectra measurements and 2-D refractive index mapping in the micro-areas near the focus were carried out. The results supported that the refractive index change induced by fs laser pulses comes from the increase of the low rank ring structures in the silicate network.