Abstract
A highly efficient (~80%), high power (18.45 W) in-band, core pumped erbium/ytterbium co-doped fiber laser is demonstrated. To the best of our knowledge, this is the highest reported efficiency from an in-band pumped 1.5 µm fiber laser operating in the tens of watts regime. Using a fitted simulation model, we show that the significantly sub-quantum limit conversion efficiency of in-band pumped erbium doped fiber amplifiers observed experimentally can be explained by concentration quenching. We then numerically study and experimentally validate the optimum pumping configuration for power scaling of in-band, cladding pumped erbium doped fiber amplifiers. Our simulation results indicate that a ~77% power conversion efficiency with high output power should be possible through cladding pumping of current commercially available pure Erbium doped active fibers providing the loss experienced by the cladding guided 1535 nm pump due to the coating absorption can be reduced to an acceptable level by better coating material choice. The power conversion efficiency has the potential to exceed 90% if concentration quenching of erbium ions can be reduced via improvements in fiber design and fabrication.
Highlights
High power 1.55 μm erbium (Er) based fiber lasers are attractive for numerous applications, such as materials processing and military applications, where light scattered off-target is a great concern in terms of eye safety
Power scaling of erbium fibers is obviously possible using higher brightness pump sources and core-pumping [12,13] and we describe experiments on an in-band, core pumped EYDF delivering 18.5 W output power at 1562.5 nm with ~80% power conversion efficiency (PCE =/absorbed pump power), which we believe to be a record PCE for a fiber laser operating in the multi-tens of Watt regime [13]
We have demonstrated better than 80% PCE from an erbium doped fiber (EDF) with low pair-induced quenching (PIQ) and further enhancement in PCE may be possible by eliminating the PIQ completely
Summary
High power 1.55 μm erbium (Er) based fiber lasers are attractive for numerous applications, such as materials processing and military applications, where light scattered off-target is a great concern in terms of eye safety. Power scaling of erbium fibers is obviously possible using higher brightness pump sources and core-pumping [12,13] and we describe experiments on an in-band, core pumped EYDF delivering 18.5 W output power at 1562.5 nm with ~80% power conversion efficiency (PCE = (output signal power-input signal power)/absorbed pump power), which we believe to be a record PCE for a fiber laser operating in the multi-tens of Watt regime [13] This approach is limited by the scalability of high power single mode pump sources and is much less desirable than diode based solutions. We validate this prediction with cladding pumped experiments identifying in the process that excess pump loss in this instance due to the high absorption by the cladding materials is an impediment to this in current commercial fibers
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