High-power red laser oscillation of 311.4 mW in Pr3+-doped waterproof fluoro-aluminate glass fibre excited by GaN laser diode

A high-power red fibre laser with a Pr-doped waterproof fluoro-aluminate glass fibre (Pr:WPFGF) is reported. Even though a Pr: WPFGF is a fluoride material, it possesses low deliquescence and enough long-term stability. A blue/violet GaN laser diode at 442 nm was launched into the Pr: WPFGF (core diameter 8 mu m, length 40 mm), both end surfaces of which were directly coated to construct a resonator. The maximum output power was measured to be 311.4 mW at 800 mW pumping power. The oscillation wavelength was 638 nm and the slope efficiency was calculated to be 41.6%. These results showed good agreement with theoretical predictions.