Single-mode visible laser oscillation in Pr-doped double-clad structured waterproof fluoro-aluminate glass fibre

A Pr-doped double-clad structured waterproof fluoride glass fibre (Pr:DC-WPFGF) was successfully drawn, and the laser oscillation was demonstrated. The maximum output power was measured as 251.7 mW at 639.0 nm. The Pr:DC-WPFGF was designed to be single-mode fibre, with 0.08 of numerical aperture and 5.2 mu m of core diameter. The beam-quality factor, M-2, was measured and evaluated to be 1.0.