Power scaling of cladding-pumped Er,Yb-doped fiber lasers at 1.5 μm

An efficient double-clad erbium-ytterbium co-doped fiber laser pumped by two high-power diode-stacks at 975nm is reported. Using a simple external cavity configuration at one end of the fiber and the 3.6% Fresnel reflection from a cleaved fiber end facet at the opposite end of the fiber to provide the necessary feedback for lasing, we obtained a maximum output power of 159W at 1565nm in a beam with beam quality factor (M2) similar to 1.9 for 466W of launched pump power. The corresponding slope efficiency with respect to launched pump power was 34%. The maximum output power was limited by the available pump power. A strategy for increasing the output power and improving the beam quality based on the use of a double-clad fiber design with a helical-core trajectory is considered.