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Proceedings Paper

On the efficiency of Tm-doped 2µm lasers
Author(s): K. van Dalfsen; S. Aravazhi; C. Grivas; S. M. García-Blanco; M. Pollnau
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Paper 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.

Paper Details

Date Published: 20 February 2015
PDF: 6 pages
Proc. SPIE 9342, Solid State Lasers XXIV: Technology and Devices, 93421U (20 February 2015); doi: 10.1117/12.2077490
Show Author Affiliations
K. van Dalfsen, Univ. Twente (Netherlands)
S. Aravazhi, Univ. Twente (Netherlands)
C. Grivas, Univ. of Southampton (United Kingdom)
S. M. García-Blanco, Univ. Twente (Netherlands)
M. Pollnau, Univ. Twente (Netherlands)
KTH Royal Institute of Technology (Sweden)

Published in SPIE Proceedings Vol. 9342:
Solid State Lasers XXIV: Technology and Devices
W. Andrew Clarkson; Ramesh K. Shori, Editor(s)

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