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On the efficiency of Tm-doped 2-mu m lasers
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2015 (English)In: Solid State Lasers XXIV: Technology and Devices, SPIE - International Society for Optical Engineering, 2015, Vol. 9342, 93421UConference paper (Refereed)
Abstract [en]

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 endfacet, 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 mu m with a maximum slope efficiency of similar to 80% was obtained. To the best of our knowledge, this result represents the most efficient 2-mu m 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-mu m 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 luminescencedecay 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 similar to 80% closely approaches this limit.

Place, publisher, year, edition, pages
SPIE - International Society for Optical Engineering, 2015. Vol. 9342, 93421U
, Proceedings of SPIE, ISSN 0277-786X
Keyword [en]
potassium double tungstate, thulium laser, 2-mu m laser, waveguide laser, cross-relaxation process, slope efficiency
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URN: urn:nbn:se:kth:diva-169161DOI: 10.1117/12.2077490ISI: 000353888400049ScopusID: 2-s2.0-84929501334ISBN: 978-1-62841-432-5OAI: diva2:820474
Conference on Solid State Lasers XXIV - Technology and Devices, FEB 08-10, 2015, San Francisco, United States

QC 20150612

Available from: 2015-06-12 Created: 2015-06-11 Last updated: 2015-06-12Bibliographically approved

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Pollnau, Markus
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Materials- and Nano Physics
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