Efficient, tunable, zero-line diode-pumped, continuous-wave Yb^3+:Ca_4LnO(BO_3)_3 (Ln = Gd, Y) lasers at room temperature and application to miniature lasers

We demonstrate an efficient cw 976-nm-diode-pumped ${\mathrm{Yb}}^{3+}:{\mathrm{Ca}}_4\mathrm{GdO}({\mathrm{BO}}_3{)}_3$ laser. At room temperature we obtained 814 mW of power with a slope efficiency of 77% and a small-signal gain per round trip of 1.67. We also demonstrate that the ${\mathrm{Yb}}^{3+}:{\mathrm{Ca}}_4\mathit{Ln}\mathrm{O}({\mathrm{BO}}_3{)}_3$ $(\mathit{Ln}=\mathrm{Gd}, \mathrm{Y})$ crystals are suitable for a plano–plano microchip-type cavity. With this microlaser we have obtained an average power of 300 mW, which corresponds to an optical–optical conversion efficiency of 27%.