Power and efficiency scaling of Er: ZBLAN fiber laser

We report on a 976 nm pumped erbium doped fluoride (Er:ZBLAN) fiber laser emitting at 2.8 µm with nearly 70 W of output power in a quasi-continuous wave (Q-CW) regime with the slope efficiency versus launched pump power of ∼20%. It is believed to be the highest Q-CW power ever demonstrated from an Er:ZBLAN fiber laser . We also present the results of a study demonstrating that the Er:ZBLAN fiber laser slope efficiency versus absorbed pump power increases monotonically with the pump wavelength from 19% to 29% over the wavelength range of 960–985 nm. The achieved slope efficiency of 29% is, to the best of our knowledge, the highest efficiency ever reported for an Er:ZBLAN fiber non-cascaded laser. (letter)