Fabrication of Yb/Ce/P co-doped fluoroaluminosilicate fiber with excellent photodarkening suppression and kW-level laser performance

A Yb/Ce/P (ytterbium/cerium/phosphorus) co-doped 20/400 µm fluoroaluminosilicate double clad fiber is fabricated by conventional modified chemical vapor deposition (MCVD) technology and solution doping process. The measurement shows the fiber core is doped with ∼0.21 mol% Yb2O3, ∼0.05 mol% Ce2O3, ∼0.83 mol% P2O5, ∼0.37 mol% SiF4 and ∼1.61 mol% Al2O3, respectively. Through co-doping a certain concentration of Ce2O3, P2O5, SiF4 and Al2O3 in the fiber core, it is found that the Yb/Ce/P co-doped 20/400 µm fluoroaluminosilicate fiber shows excellent photodarkening (PD) suppression, and PD loss is about 0 dB/m at 633 nm. Based on an all-fiber laser oscillator system and pumped directly by 915 nm laser diodes, a 1.9 kW laser at 1080 nm is achieved with slope efficiency is about 77.1% (pumped at 915 nm), and the beam factor of M2 is 1.32, which clearly reveals that the Yb/Ce/P co-doped fluoroaluminosilicate fiber is a promising candidate for laser applications with enhanced PD resistivity.