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Proceedings Paper

Grating waveguide structures for intracavity generation of beams with azimuthal polarization in an Yb:YAG thin-disk laser
Author(s): Martin Rumpel; Marwan Abdou Ahmed; Andreas Voss; Thomas Graf
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Paper Abstract

We report on the design, fabrication, and spectroscopic characterization as well as on the intra-cavity employment of grating waveguide structures (GWS) for the generation of beams with azimuthal polarization in an Yb:YAG thin-disk laser. Two different GWS concepts are used for the polarization shaping: the first is based on a resonant reflection (RR) behavior whereas the second uses the coupling mechanism to a leaky-mode (LM) similar to what was published for the generation of radially polarized beams1. In both cases the structure combines a multilayer coating and a sub-wavelength grating. The RR structure comprises a partial reflector (R ≈ 88%) and a wave guiding layer. The parameters of the grating (which is integrated into all layers) are designed in order exploit the abnormal reflection caused by constructive interference and was designed with a nominal peak reflectivity higher than 99.99% at the laser wavelength of 1030 nm and within a narrow spectral bandwidth of 2-3 nm FWHM. The LM structure is composed of a standard HR mirror and a grating which was designed to excite a leaky mode of the plane structure. This leads to a reduction of the reflectivity for one polarization at the design wavelength of 1030 nm whereas the orthogonal polarization is not affected and experiences an unchanged high reflectivity. By fabricating these elements with circular grating lines one can generate beams with either radial or azimuthal polarization. Here we discuss the latter case, where azimuthally polarized beams with a laser output power of up to 145 W, an optical laser efficiency of 43%, and high polarization purity were generated. The beam quality factor M2 of the emitted beams was measured to be ≈ 2.3. Moreover, the effect of the heat load in the GWS on its performance will be discussed.

Paper Details

Date Published: 15 May 2012
PDF: 12 pages
Proc. SPIE 8433, Laser Sources and Applications, 84331A (15 May 2012); doi: 10.1117/12.922228
Show Author Affiliations
Martin Rumpel, Univ. Stuttgart (Germany)
Marwan Abdou Ahmed, Univ. Stuttgart (Germany)
Andreas Voss, Univ. Stuttgart (Germany)
Thomas Graf, Univ. Stuttgart (Germany)

Published in SPIE Proceedings Vol. 8433:
Laser Sources and Applications
Thomas Graf; Jacob I. Mackenzie; Helena Jelínková; John Powell, Editor(s)

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