The investigation of the photo-inscription of waveguides in Barium Gallo-Germanate glass (BGG: BaO, GeO2, Ga2O3) is presented. This type of glass has been chosen because of its robustness, its chemical stability and its transmission throughout the whole visible region up to 5 µm. Irradiation with a focused femtosecond laser pulse train of different BGG samples leads to relatively high positive refractive index changes over a wide range of exposure conditions. Waveguides with a controllable diameter ranging from 4 to 35 µm and index change up to 10-2 were inscribed. A glass sample with custom molecular composition, adding a halogen component to remove hydroxyl ions and reduce the absorption band near 3 µm, was fabricated.
Inscription of low-loss waveguides was performed, supporting only two transverse modes at the wavelength of 2.78 µm, and matching well with single-mode fluoro-zirconate fibres at this wavelength. An upper bound for the propagation losses of 0.5±0.1 dB/cm was determined along the waveguides, mainly due to absorption of hydroxyl ions in the glass, which can further be reduced by improving the purification process. The results presented show the great potential of the BGG glass family for the fabrication of core waveguides operating in the 2-5 µm spectral range and open a pathway towards the integration of mid-IR photonic devices based on BGG glasses.