Waveguides and nonlinear index of refraction of borate glass doped with transition metals

• A new composition of borate glass containing ZnO, PbO and Nb2O5 has been developed.
• Fs-laser was used to produce 3D waveguides and study the nonlinear refractive index.
• The main contribution for n2 is from the glass matrix, being 4.5 × 10−20 m2/W from VIS-NIR.
• The waveguide in Fe doped glass has a total loss of 0.6 ± 0.1 dB/mm at 632.8 nm.

The ability to write 3D waveguides by femtosecond laser micromachining and the nonlinear refractive index (n2) spectrum of a new borate glass matrix, containing zinc and lead oxides – (BZP) have been investigated. The transparent matrix was doped with transition metals (CdCl2, Fe2O3, MnO2 and CoO) in order to introduce electronic transitions in visible spectrum, aiming to evaluate their influence on the waveguides and n2 spectrum. We observed that n2 is approximately constant from 600 to 1500 nm, exhibiting an average value of 4.5 × 10−20 m2/W, which is about twice larger than the one for fused silica. The waveguide profile is influenced by the self-focusing effect of the matrix owing to its positive nonlinear index of refraction in the wavelength used for micromachining. A decrease in the waveguide loss of approximately four times was observed for the sample doped with Fe in comparison to the other ones, which may be associated with the change in the optical gap energy.