Beirow, FriederEckerle, MichaelDannecker, BenjaminDietrich, TomAbdou Ahmed, MarwanGraf, Thomas2018-03-082018-03-0820181094-4087500657637http://nbn-resolving.de/urn:nbn:de:bsz:93-opus-ds-97007http://elib.uni-stuttgart.de/handle/11682/9700http://dx.doi.org/10.18419/opus-9683We report on a high-power passively mode-locked radially polarized Yb:YAG thin-disk oscillator providing 125 W of average output power. To the best of our knowledge, this is the highest average power ever reported from a mode-locked radially polarized oscillator without subsequent amplification stages. Mode-locking was achieved by implementing a SESAM as the cavity end mirror and the radial polarization of the LG*01 mode was obtained by means of a circular Grating Waveguide Output Coupler. The repetition rate was 78 MHz. A pulse duration of 0.97 ps and a spectral bandwidth of 1.4 nm (FWHM) were measured at the maximum output power. This corresponds to a pulse energy of 1.6 μJ and a pulse peak power of 1.45 MW. A high degree of radial polarization of 97.3 ± 1% and an M2-value of 2.16 which is close to the theoretical value for the LG*01 doughnut mode were measured.eninfo:eu-repo/semantics/openAccess500article