Grating waveguide structures for intracavity generation of beams with azimuthal polarization in an Yb:YAG thin-disk laser

Martin Rumpel; Marwan Abdou Ahmed; Andreas Voss; Thomas Graf

doi:10.1117/12.922228

15 May 2012 Grating waveguide structures for intracavity generation of beams with azimuthal polarization in an Yb:YAG thin-disk laser

Martin Rumpel, Marwan Abdou Ahmed, Andreas Voss, Thomas Graf

Author Affiliations +

Proceedings Volume 8433, Laser Sources and Applications; 84331A (2012) https://doi.org/10.1117/12.922228
Event: SPIE Photonics Europe, 2012, Brussels, Belgium

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.

Citation Download Citation

Martin Rumpel, Marwan Abdou Ahmed, Andreas Voss, and Thomas Graf "Grating waveguide structures for intracavity generation of beams with azimuthal polarization in an Yb:YAG thin-disk laser", Proc. SPIE 8433, Laser Sources and Applications, 84331A (15 May 2012); https://doi.org/10.1117/12.922228

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