On the efficiency of Tm-doped 2-µm lasers

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

    Research output: Chapter in Book/Report/Conference proceedingConference contributionAcademic

    Abstract

    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
    PublisherSPIE
    PagesPaper 93421U
    Number of pages6
    ISBN (Print)978-1-62841-432-5
    DOIs
    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
    PublisherSPIE
    Volume9342

    Conference

    ConferenceSolid State Lasers XXIV 2015
    CountryUnited States
    CitySan Francisco
    Period6/02/1512/02/15

    Keywords

    • 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

    Cite this

    van Dalfsen, K., Aravazhi, S., Grivas, C., García Blanco, S. M., & Pollnau, M. (2015). On the efficiency of Tm-doped 2-µm lasers. In Solid State Lasers XXIV (pp. Paper 93421U). (Proceedings of the SPIE; Vol. 9342). Bellingham, USA: SPIE. https://doi.org/10.1117/12.2077490