Abstract

Major reported power scaling in the eye-safe ~1.5 μm fiber lasers has been based on the cladding pumped Yb-Er-co-doped fibers pumped into Yb-absorption band [1]. Very few results are known on the resonantly cladding-pumped Yb-free Er-doped fibers - the approach, which can actually offer much higher efficiency as well as power scalability due to very low quantum defect (QD) and, hence, potentially QD-limited efficiency operation and much lower pump-induced heat deposition [2-4]. The [3] was the first known effort exploiting the most scalable LMA fiber approach. The [4] was the first effort to scale significantly beyond the ~1 W power level. Single-frequency output power of 9.3 W was obtained in a MOPA configuration from resonantly cladding-pumped Yb-free EDFA with the optical-to-optical conversion slope efficiency of ~46% [4]. This efficiency, obtained with the commercially available (COTS) highly concentrated Er-doped fibers happened to be the highest reported on Er-doped fibers before [4], but it surely is not sufficient to support the expected QD-limited operation. Power scaling to the ~47 W output power level at 1590 nm was achieved recently [5], which additionally points to significant scaling potential of the above approach.

© 2009 IEEE