Anisotropy in laser performance of Yb:GdCa4O(BO3)3 crystal

We report distinct laser performance of Yb:GdCa4O(BO3)(3) crystals cut along different principal optical axes using an unpolarized diode pump. The continuous-wave (cw) laser oscillation generated with y-cut crystal is polarized either with E parallel to x or with E parallel to z depending on the output coupling (T) utilized; a specific T = 3% leads to a special situation in which the two orthogonal polarization states coexist oscillating at different wavelengths. The laser oscillation achieved with x- and z-cut crystals is also polarized, but with a fixed polarization of E parallel to z and E parallel to x, respectively. The most efficient laser operation is obtained with the y-cut crystal, generating a cw output power of 73.5 W at 1083-1085 nm with an optical-to-optical efficiency of 63%, the slope efficiency being as high as 84%. (C) 2008 Optical Society of America.