The thin-disk laser (TDL) is a promising solid state laser concept since it combines good power scalability with high efficiency and small thermal lensing effects. Therefore this concept is a good candidate for near diffraction limited multi-kilowatt operation. In addition, due to its low depolarization losses, the TDL can be operated polarized without sacrificing its efficiency. To exploit the full potential of the TDL concept, the small thermally induced wave front distortions of the disk have to be compensated. At the same time, the intensity distribution of the output beam can be formed according to the requirements of the application. The wave front can be either corrected by a static graded-phase mirror or by an adaptive mirror. For the TDL, a thermally driven adaptive mirror was developed. The polarization state of the radiation field is another important aspect which can be optimized for specific processes. For example, a radially polarized beam promises significantly increased process efficiency for cutting sheet metal. The polarization state oscillating inside the resonator can be controlled by means of a polarization selective resonant grating-waveguide mirror. We describe the successive steps of development towards optical elements optimized for the intra-cavity beam shaping of the TDL.
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