Widely wavelength-tunable electro-optical Q-switched Er³⁺:ZBLAN fiber laser emitting near 2.8  µm

Mid-infrared (MIR) pulsed fiber lasers are widely used because their wavelengths match the molecular fingerprint region and have strong absorption peaks in water. In this work, to our knowledge, the first MIR fiber laser with tunable wavelength and electro-optical Q-switching is demonstrated by using a <i>L</i><i>a</i>₃<i>G</i><i>a</i>₅<i>S</i><i>i</i><i>O</i>₁₄ crystal. The stable Q-switched pulses can be tuned smoothly over a wavelength range of 2705.6-2824.8 nm. The 119.2 nm tuning range is the widest recorded for Q-switched <i>E</i><i>r</i>³⁺-doped fiber lasers operating around the 2.8 µm band. At a pump power of 3.6 W and a repetition rate of 10 kHz, the laser produces an average output power of 274.5 mW with a pulse width of 17.4 ns. The calculated maximum pulse energy is ∼27.5µ<i>J</i>, with a maximum peak power of ∼1.6<i>k</i><i>W</i>. Additionally, the signal-to-noise ratio (SNR) is 54 dB, demonstrating excellent pulse stability. The wide tunable range, narrow pulse width, and good stability demonstrate that it is possible to develop an efficient wavelength-tunable MIR pulsed laser using electro-optical Q-switching. These features make it highly promising for applications in laser surgery, polymer processing, and free-space communications.