Recent advances in 3.5 μm erbium-doped mid-infrared fiber lasers

The performance of mid-infrared Er³⁺-doped fiber lasers has dramatically improved in the last few years. In this paper we present an overview of the progress in 3.5 μm fiber lasers based on the dual-wavelength pumping approach. The cross-section of the excited state absorption transition used by the 1973 nm second pump is found experimentally. A numerical simulation of the expected Q-switched behavior of this fiber laser is presented. This shows that increasing the power of the 977 nm pump is important to achieve high peak power pulses.