Yb/Ce Codoped Aluminosilicate Fiber With High Laser Stability for Multi-kW Level Laser

Further power scaling and stable laser performance were demonstrated in the Yb/Ce codoped aluminosilicate fiber fabricated through low-temperature chelate gas phase deposition technique. The molar ratio of Ce/Yb was designed and optimized to be 0.58 for low background loss, effective photodarkening suppression, and no additional thermal load. The background loss of this active fiber was 4.7 dB/km and its photodarkening loss at equilibrium was as low as 3.9 dB/m at 633 nm. Benefiting from low-temperature deposition technique, the fiber showed uniform core composition devoid of clustering and central ‘dip’ of refractive index profile and 0.19 mol% Yb
₂
O
₃
was homogeneously dissolved into the fiber core plus with 0.41 mol% Al
₂
O
₃
, 0.11 mol% Ce
₂
O
₃
, and 0.32 mol% SiF
₄
. Based on a master oscillator power amplifier laser setup, 5.04 kW laser output at 1079.80 nm was achieved with a slope efficiency of 81.1%. Stabilized at 5kW-level laser for over 60 minutes, the output power presented almost no power degradation, directly confirming a noticeable photodarkening mitigation.