Radially polarized beams with an output power of 275 W, M2=2.3 and an efficiency of about 52.5% were generated from an Yb:YAG thin-disk laser. An intra-cavity circular resonant waveguide grating was used as a polarization selective mirror inside the laser cavity. We report on the design and the fabrication using a scanning beam interference lithography system and discuss the calculated and measured performances of the presented polarizing grating mirrors.