On the efficiency of Tm-doped 2-µm lasers

Koop van Dalfsen, S. Aravazhi, C. Grivas, Sonia Maria García Blanco, Markus Pollnau

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    A potassium double tungstate layer with the composition KY0.40Gd0.29Lu0.23Tm0.08(WO4)2 was grown onto a pure KY(WO4)2 substrate by liquid-phase epitaxy, microstructured by standard lithography and Ar-ion etching, and overgrown by a pure KY(WO4)2 layer. The end-facets were polished. Laser experiments were performed on these buried, ridge-type channel waveguides in a resonator with one butt-coupled mirror and Fresnel reflection from the other end-facet, resulting in a high output-coupling degree of 89%, compared to intrinsic round-trip losses of only 2%. By pumping with a Ti:Sapphire laser at 794 nm, 1.6 W of output power at 1.84 μm with a maximum slope efficiency of ~80% was obtained. To the best of our knowledge, this result represents the most efficient 2-μm channel waveguide laser to date. We determined the optimum Tm3+ concentration in double tungstate channel waveguides to be at least 8at.% for efficient lasing. The theoretical limit of the slope efficiency depends on the Stokes efficiency which here is 43.2%, the outcoupling efficiency which here is 99%, and the pump quantum efficiency. The pump quantum efficiency of a 2-µm Tm3+ laser pumped around 800 nm hinges on the efficiency of its cross-relaxation process. By fitting the macroscopic cross-relaxation parameter which linearly depends on the Tm3+ concentration to concentration-dependent luminescence-decay data, calculating the overall decay rate of the pump level, and deriving the concentration-dependent pump quantum efficiency, we obtain a theoretical limit for the slope efficiency of 83% for the chosen Tm3+ concentration. The experimental slope efficiency of ~80% closely approaches this limit.
    Original languageUndefined
    Title of host publicationSolid State Lasers XXIV
    Place of PublicationBellingham, USA
    PagesPaper 93421U
    Number of pages6
    ISBN (Print)978-1-62841-432-5
    Publication statusPublished - Apr 2015
    EventSolid State Lasers XXIV 2015 - San Francisco, United States
    Duration: 6 Feb 201512 Feb 2015
    Conference number: 24

    Publication series

    NameProceedings of the SPIE


    ConferenceSolid State Lasers XXIV 2015
    Country/TerritoryUnited States
    CitySan Francisco


    • slope efficiency
    • EWI-25964
    • IOMS-APD: Active Photonic Devices
    • 2-µm laser
    • IR-95790
    • Potassium double tungstate
    • thulium laser
    • cross-relaxation process
    • METIS-312573
    • Waveguide laser

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