Diode-pumped 1 018-nm ytterbium-doped double-clad f iber laser

We report a 1 018-nm ytterbium-doped double-clad fiber laser pumped by 970-nm diode.A pair of fiber Bragg gratings with reflectivities of 99.9% and 9% at a center wavelength of 1 018.9 nm are employed as cavity mirrors.The ytterbium-doped double-clad fiber is a 2.6-m-long Liekki fiber.Laser output power of 7.5 W at 1 018 nm is obtained under the pump power of 59.2 W. The overall slope efficiency of the fiber laser is about 16%.This low slope efficiency is mainly due to the incomplete absorption of the pump power.