Lasing in a femtosecond-laser-written single-scan waveguide fabricated in Tm-doped BGG glass

We report lasing action in a femtosecond-laser-inscribed waveguide in thulium-doped barium-gallium-germanium oxide (BGG) glass. A laser cavity was assembled with this waveguide that provided a single-mode output of 62 mW when pumped at 1.6 µm. The waveguide was fabricated using a single laser scan to create a near-circular cross section with a positive refractive index change of approximately 3.5 × 10^-3. Analysis of the laser-modified region was performed using electron-probe microanalysis and Raman spectroscopy. These findings establish BGG glass as a promising platform for the fabrication of mid-infrared integrated photonic devices.