title: Progress in rare-earth-doped mid-infrared fiber lasers.
abstract: The progress, and current challenges, in fabricating rare-earth-doped chalcogenide-glass fibers for developing mid-infrared (IR) fiber lasers are reviewed. For the first time a coherent explanation is forwarded for the failure to date to develop a gallium-lanthanum-sulfide glass mid-IR fiber laser. For the more covalent chalcogenide glasses, the importance of optimizing the glass host and glass processing routes in order to minimize non-radiative decay and to avoid rare earth ion clustering and glass devitrification is discussed. For the first time a new idea is explored to explain an additional method of non-radiative depopulation of the excited state in the mid-IR that has not been properly recognized before: that of impurity multiphonon relaxation. Practical characterization of candidate selenide glasses is presented. Potential applications of mid-infrared fiber lasers are suggested.
authors.affiliation: Novel Photonic Glasses Group, George Green Institute for Electromagnetics Research, Electrical Systems and Optics Research Division, Faculty of Engineering, University Park, University of Nottingham, Nottingham NG7 2RD, UK. angela.seddon@nottingham ac.uk
authors.forename: Angela B
authors.initials: AB
authors.lastname: Seddon
authors.forename: Zhuoqi
authors.initials: Z
authors.lastname: Tang
authors.forename: David
authors.initials: D
authors.lastname: Furniss
authors.forename: Slawomir
authors.initials: S
authors.lastname: Sujecki
authors.forename: Trevor M
authors.initials: TM
authors.lastname: Benson
mesh_terms: D018011:Chalcogens / Q000737:chemistry*; D003198:Computer Simulation; D017076:Computer-Aided Design; D003460:Crystallization; D004867:Equipment Design; D019544:Equipment Failure Analysis; D005336:Fiber Optic Technology / Q000295:instrumentation*; D005898:Glass / Q000737:chemistry; D007259:Infrared Rays; D007834:Lasers; D008674:Metals, Rare Earth / Q000737:chemistry*; D008904:Miniaturization; D008962:Models, Theoretical; D012031:Refractometry / Q000295:instrumentation*
chemical_list: D018011:Chalcogens; D008674:Metals, Rare Earth