660 nm and 974 nm Dual-Wavelength Pumped Er³⁺/Dy³⁺ Codoped ZBLAN Fiber Laser

In this work, we experimentally report a wavelength -tunable Er<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup>/Dy<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> codoped ZBLAN fiber laser via employing the strategy of 660 nm and 974 nm dual-wavelength pumping, for the first time, to our knowledge. Based on the combined effects of the <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup>F<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9/2</sub>→<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">4</sup>I<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">9/2</sub> and <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup>H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">13/2</sub>→<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">6</sup>H<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">15/2</sub> transitions from Er<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> and Dy<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3+</sup> ions, respectively, the tunable spectral range of 2930~3681 nm (751 nm) was obtained, representing the broadest level of rare-earth-doped mid-infrared fiber lasers. More importantly, the gain distribution of the laser could be managed by controlling the ratio of the dual-wavelength pump powers, hence yielding an ultraflat subrange of 3.2~3.4 μm, with a low power fluctuation of <3% around 700 mW. This dual-wavelength pumped architecture provides an optional mid-infrared photonics platform for designing broadband tunable oscillators and amplifiers.