A new crystalline medium for 1.5 ?m Yb-Er lasers is proposed: GdCa<sub>4</sub>O(BO<sub>3</sub>)<sub>3</sub> (GdCOB). Its melting point allows crystal growth using platinum instead of iridium crucibles. Spectroscopic and laser tests of the new material are described. A maximum CW output power of 80 mW was achieved in a monolithic microchip cavity under laser diode pumping.
© 2004 Optical Society of America