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Proceedings Paper

Efficient generation of cylindrically polarized beams in an Yb:YAG thin-disk laser enabled by a ring-shaped pumping distribution
Author(s): Tom Dietrich; Martin Rumpel; Thomas Graf; Marwan Abdou Ahmed
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Paper Abstract

The efficient generation of a cylindrically (radially or azimuthally) polarized LG01 mode was investigated using a ring-shaped pumping distribution in a high-power Yb:YAG thin-disk laser setup. This was realized by implementing a 300 mm long customized fused silica fiber capillary in the pump beam path of the pumping optics of a thin-disk laser. Furthermore, a grating waveguide mirror based on the leaky-mode coupling mechanism was used as one of the cavity end mirrors to allow sufficient reduction of the reflectivity of the polarization state to be suppressed in the resonator. In order to achieve efficient laser operation, an optimized mode overlap between the ring-shaped pump spot and the excited first order Laguerre-Gaussian doughnut mode is required. This was investigated theoretically by analyzing the intensity distribution generated by different fiber geometries using a commercially raytracing software (Zemax). The output power, polarization state and efficiency of the emitted laser beam were compared to that obtained with a standard flattop pumping distribution. In particular, the thermal behavior of the disk was investigated since the excessive fluorescence caused by the non-saturated excitation in the center of the homogeneously pumped disk leads to a strong heating of the crystal. This considerable heating source is avoided in the case of the ring-shaped pumping and a reduction of the temperature increase on the disk surface of about 21% (at 280 W of pump power) was observed. This should allow higher pump power densities without increasing the risk of damaging the disk or distorting the polarization purity. With a laser efficiency of 41.2% to be as high as in the case of the flattop pumping, a maximum output power of 107 W was measured.

Paper Details

Date Published: 27 April 2016
PDF: 8 pages
Proc. SPIE 9893, Laser Sources and Applications III, 98930M (27 April 2016); doi: 10.1117/12.2230682
Show Author Affiliations
Tom Dietrich, Univ. Stuttgart (Germany)
Martin Rumpel, Univ. Stuttgart (Germany)
Thomas Graf, Univ. Stuttgart (Germany)
Marwan Abdou Ahmed, Univ. Stuttgart (Germany)

Published in SPIE Proceedings Vol. 9893:
Laser Sources and Applications III
Jacob I. Mackenzie; Helena JelÍnková; Takunori Taira; Marwan Abdou Ahmed, Editor(s)

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