We report on the design, fabrication, and implementation of grating-waveguide structures (GWS) for intracavity polarization and wavelength selection as well as wavelength tuning. The GWS discussed in this Letter is a combination of a low-index leaky-mode waveguide, a subwavelength diffraction grating, and a highly reflective mirror that was designed to operate in Littrow configuration. Using our device as the end mirror of an Yb:YAG thin-disk laser allowed the extraction of beams that exhibit an extremely narrow laser emission bandwidth of FWHM and a high degree of linear polarization of . Moreover, the GWS allows a wavelength tuning range from 1007 to 1053 nm. The high-power suitability and the low loss of the GWS was demonstrated by the intracavity use in an Yb:YAG thin-disk laser with an output power of 325 W in multimode operation () and with 110 W in fundamental-mode operation (), exhibiting optical efficiencies of 53.2% and 36.2%, respectively. An output power of 1.8 kW, corresponding to a power density of 125 kW/cm2 on the grating, was achieved in further higher-power experiments.
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