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Proceedings Paper

Thin-disk-laser-pumped ytterbium-doped fiber laser with an output power in the kW range
Author(s): A. Popp; A. Voss; Th. Graf; S. Unger; J. Kirchhof; H. Bartelt
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Paper Abstract

We report on an ytterbium-doped fiber laser (FL) pumped by an Yb:YAG thin disk laser [1]. The FL essentially acts as a brilliance converter suitable for applications requiring a diffraction limited kilowatt-class laser source. The FL can be positioned close to the application at the end of a multimode delivery fiber, which solves the length limitation of highpower single-mode delivery caused by non-linear effects in the fibers. The 11 m long fiber used in the experiments has a highly doped (1.3•1026 ions/m3) core with a diameter of 30 μm surrounded by a circular cladding with a diameter of 100 μm. The core has a N.A. of 0.06 and a V-parameter of 5.2. A commercial thin disk laser with a BPP of 4 mm•mrad is used as pump source. At the wavelength of 1030 nm, the pump light absorption is 1.4 dB/m, which is 77 times lower than the peak value at 976 nm. So far, a maximum cw output power of 925 W has been achieved at a pump power of 1203 W [2]. The output power was limited by the incomplete conduction cooling of the fiber and the temperature stability of the acrylate coating. With single pass pumping, an absolute efficiency of 77 % was achieved in good agreement with the simulation result of 81 %. Double-pass pumping will further increase the efficiency. The M2 was measured to be 2.6 with the fiber coiled on a 120 mm diameter cylinder. With a fully optimized fiber, having a smaller V-number and an octagonal pump cladding, an efficiency of 85 % and a beam quality of M2 < 1.5 are expected. We present the preliminary results achieved with a commercially available fiber as well as the recent results obtained with an improved active fiber as described above.

Paper Details

Date Published: 17 May 2010
PDF: 12 pages
Proc. SPIE 7721, Solid State Lasers and Amplifiers IV, and High-Power Lasers, 772102 (17 May 2010); doi: 10.1117/12.854321
Show Author Affiliations
A. Popp, Univ. Stuttgart (Germany)
A. Voss, Univ. Stuttgart (Germany)
Th. Graf, Univ. Stuttgart (Germany)
S. Unger, IPHT Jena (Germany)
J. Kirchhof, IPHT Jena (Germany)
H. Bartelt, IPHT Jena (Germany)

Published in SPIE Proceedings Vol. 7721:
Solid State Lasers and Amplifiers IV, and High-Power Lasers
Thomas Graf; Gerhard G. Paulus; Jacob I. Mackenzie; Vincent Bagnoud; Catherine Le Blanc; Helena Jelinkov√°, Editor(s)

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