Erbium-doped ZBLAN fiber laser pumped at 1.7 µm for emission at 2.8 µm.

In this paper, a novel, to the best of our knowledge, efficient pump scheme for an erbium-doped fluoride fiber laser with emission at 2.8 µm in the mid-infrared region is proposed and demonstrated. A singular pump source at 1.7 µm is used to excite Er ions from ground state I to lower laser level I, and then further boost the ions to I, where a non-radiation transition occurs for the Er ions to reach upper laser level I. This scheme can efficiently recycle ions on the lower laser level I by excited-state absorption, therefore realizing population inversion and enhancing laser efficiency. In our demonstration, a 660-mW laser output at 2.8 µm is achieved from a 1.7-µm core-pumped erbium-doped fluoride fiber laser, where the slope efficiency versus launched pump power is 23.7%. The proposed innovative pump scheme shows great potential to realize high-power, high-efficiency erbium-doped fiber lasers at 2.8 µm.