Design of ZBLAN Dy-Doped Fiber Laser in the 560-600nm Band

Yellow Dy-doped ZBLAN fiber lasers emitting in the 560600 nm window is highly desirable for biomedical imaging, laser display, lidar and atmospheric sensing, yet their performance is still limited by sub-optimal gain design. Here we present an optimization of the Dy: ZBLAN fiber laser that simultaneously tunes the dopant concentration and the linear-cavity length. A four-level rate-equation model was established and coupled with pump-power and signal-power propagation equations; the system was numerically solved in MATLAB with experimentally reported spectroscopic parameters. Parametric sweeps show that increasing the Dy concentration from51024m-3to21025m-3and adjusting the cavity to 5 m maximizes population inversion while keeping re-absorption loss low. At the identified optimum the laser reaches an external slope efficiency of 38 % and produces 3.77 W of continuous-wave output at 574 nm when pumped with 10 W at 453 nm; the lasing threshold is about equal to 1 W, and no backward pump is required. The model also predicts a nearly linear outputpump characteristic and negligible backward signal, confirming good unidirectional operation. These results provide clear design rules for watt-level, narrow-band yellow fiber lasers and lay the groundwork for compact sources in advanced photonic applications.