Effects of ion clustering and excited state absorption on the performance of Ho-doped fiber lasers

Abstract

The effects of ion clustering and excited state absorption occurring in holmium doped fiber lasers are investigated experimentally and theoretically. It is found that the slope efficiencies of holmium-doped fiber lasers are reduced by inhomogeneous upconversion associated with the clustering of Ho3+ ions. Via theoretical analysis based upon Judd-Ofelt theory. it is also found that the effect of excited state absorption on the performance of Ho doped fiber lasers is negligible, a fact indicating that ion clustering is the dominant cause of the lower-than-expected slope efficiencies observed in holmium-doped fiber lasers. We argue that ion clustering is an intrinsic flaw of holmium-doped fibers and is difficult to eliminate, because our research efforts arc based on commercially available low-concentration fiber, which is fabricated with state-of-the-art techniques. (C) 2019 Optical Society of America under the terms of the OSA Open Access Publishing Agreement