Lasing action at around 1.9 μm from an ultrafast laser inscribed Tm-doped glass waveguide.

We report optical guiding and laser action at around 1.9 μm in a Tm³⁺-doped fluorogermanate glass waveguide fabricated using ultrafast laser inscription. A monolithic laser cavity was constructed by directly butt coupling dielectric mirrors to each facet of the 6.0 mm long Tm³⁺-doped waveguide. When the waveguide was pumped by a Ti:sapphire laser tuned to 791 nm, laser oscillation was achieved at around 1.91 μm. This waveguide laser exhibited a maximum slope efficiency of 6% and a maximum output power of 32 mW when pumped with 620 mW of incident laser power.