Novel Near-infrared Pump Wavelengths for Dysprosium Fiber Lasers

We report two new near-infrared pump wavelengths at 0.8 μm and 0.9 μm for dysprosium (Dy
³⁺
)-doped mid-infrared fiber lasers, which are free from detrimental pump excited state absorption that has limited all previous Dy
³⁺
fiber lasers using longer near-infrared pump wavelengths (i.e., 1.1 μm, 1.3 μm, and 1.7 μm). The maximum measured laser slope efficiencies were 18.5% and 23.7% with respect to launched pump power for 0.8 μm and 0.9 μm pump wavelengths, respectively. These new pump wavelengths provide higher fractional Stokes limits (which are 70% and 79% for 0.8 μm and 0.9 μm pumping wavelengths, respectively) than previous demonstrations. While our measured efficiencies are still below the Stokes limit, we have identified the causes to be background loss and multi-mode behaviour at the pump wavelengths; both easily solvable for future systems. A numerical model was used to confirm performance, paving the way to efficient future near-infrared-pumped, potentially diode-pumped Dy
³⁺
fiber lasers emitting in the mid-infrared.