Mid-infrared (MIR) fiber lasers hold great promise for several applications in the environment and the biomedical sectors. Now, most of these applications present high requirements in terms of average or peak power, pulse energy, or in terms of spectrum coverage. To date, laser emission from mid-IR fiber lasers at wavelength longer than 2.5 μm were mainly obtained from fluorozirconate glass optical fibers doped with either Er ⁺³ , Ho ⁺³ or Dy ⁺³ rare-earth ions. In particular, the Er ⁺³ ion has shown trend exceeding performances in the neighborhood of both 3.0 and 3.5μm . Accordingly, 42W of output power near the O-H molecular bond fundamental absorption peak as well as nearly 6W at the peak of the C-H molecular bond absorption were reported. Mid-IR fiber laser pulsed counterparts were also developed involving both Q-switched and gain-switched regimes of operation and leading to pulsed output in the ns range near both 3.0 and 3.5 μm. Pulse energies exceeding the 100 mJ level with an average power of 10 W were namely produced from a rugged monolithic cavity operating at 2825 nm. The femtosecond regime was also studied via a fiber based ring laser cavity and 207 fs pulses with 3.5 kW peak power near 2.8 μm were obtained. This femtosecond FL was subsequently used to seed an Er ⁺³ -doped-fiber amplifier, resulting (via the soliton self-frequency shift process) in a watt level femtosecond fiber source tunable from 2.8 to 3.6μm .

A survey of the previous recent developments in both cw and pulsed Mid-Infrared fiber lasers will be presented.