Abstract
Efficient cladding-pumped three-level Yb fiber lasers are difficult to achieve due to the competing four-level system and necessary high inversions. We demonstrate an efficiency of versus a coupled pump, a record for cladding-pumped fiber lasers with a single-pass pump. 84 W at with was achieved, a record power for flexible fibers. Amplified spontaneous emission was suppressed by . The efficiency is quantum-limited versus an absorbed pump. This is made possible by the use of a photo-darkening-free Yb phosphosilicate core and recent progress in single-mode large-core all-solid photonic bandgap fiber designs, which provide the necessary large core-to-cladding ratio and suppression of the four-level system.
© 2019 Optical Society of America
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