Output-coupling-dependent polarization state of a continuous-wave Yb:YCa_4O(BO_3)_3 laser

High-power continuous-wave laser operation was demonstrated with a y-cut Yb:YCa(4)O(BO(3))(3) crystal, showing critical dependence on the output coupler used. Polarized laser oscillation with E||x was obtained at 1085.6 nm by using a coupler of 0.5% transmission, yielding an output power of 7.3 W with an optical-to-optical efficiency of 63%. Higher output couplings (>/=2%) led to polarized oscillation with E||z at laser wavelengths </= 1055.5 nm, the highest output power was 6.5 W. Dual-wavelength operation in the two polarization states was realized with a coupler of 1% transmission, the output powers for the two orthogonal polarizations were 3.15 W at 1084.3 nm (E||x) and 3.45 W at 1061.3 nm (E||z). The slope efficiency for output couplers with transmission in the 0.5%-2% range was 81%-83%.