Dispersion-Managed Wavelength-Switchable and Tunable Figure-9 Er: Fiber Laser

Wavelength-switchable and tunable fiber lasers are widely applied for their flexible output performance, but their realization remains constrained by factors such as gain bandwidth, dispersion effects, and gain competition. In this work, leveraging the inherent dual-peak gain profile of Er: fiber in conjunction with the controllable cavity end-mirror reflection loss, we investigate the laser characteristics of the wavelength-switchable and tunable ultrashort pulses in an all-polarization-maintaining (PM) figure-9 fiber laser across different dispersion regions (from −0.1127 ps<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup> to +0.0227 ps<sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sup>) in the 1.5 μm waveband for the first time, to the best of our knowledge. Specifically, the laser can generate single-wavelength pulses in both anomalous and normal dispersion regions, with the central wavelength switchable between 1532 nm and 1557 nm. In the near-zero dispersion region, switchable synchronous dual-wavelength pulses can be achieved by balancing wavelength-related gain and loss, and such pulses have a 2 nm tuning range. In addition, the generation and evolution of pulse states in different dispersion regions have been simulated by establishing the corresponding theoretical model, showing excellent agreement with the experimental results. Our results deepen the understanding of gain dynamic traits and provide a foundation for studying mode-locking nonlinear evolutionary paths and dual-wavelength generated behavior.