Disordered Yb:GdYCOB crystal: Polarized spectroscopy, thermal lensing and diode-pumped lasers

We report on the Czochralski growth, polarized optical spectroscopy, thermal lensing and diode-pumped laser operation of a Yb3+-doped monoclinic "mixed" calcium rare-earth oxoborate crystal, Gd0.235Y0.672Yb0.093Ca4O(BO3)(3) (Yb:GdYCOB). The absorption, stimulated-emission and gain cross-section spectra are determined for light polarizations E || X, Y, Z. The maximum sigma(SE) above the zero-phonon line is 0.61 x 10(-20) cm(2) at 1022.4 nm (for E || Z) and the luminescence lifetime of Yb3+ ions is 2.37 ms. The gain spectra of Yb:GdYCOB extend beyond 1.15 mu m. The thermal lens is studied for the three principal cuts, X-cut, Y-cut and Z-cut, and it is found to be positive. A continuous-wave diode-pumped X-cut Yb:GdYCOB laser generates 9.27 W at similar to 1050 nm with a slope efficiency of 68.2%, linear laser polarization (E || Z) and nearly diffraction-limited beam (M-x,y(2) < 1.16). A continuous wavelength tuning from 1020.9 to 1086.3 nm (a tuning range of similar to 65 nm) is achieved for the Z-cut crystal and the laser polarization E || X.