Rational Design of Yb3+-Doped Quaternary Fluorophosphate Glass Fiber via a Phase Diagram-Based Predictive Framework

The rational design of multicomponent laser glasses in high-dimensional compositional spaces remains a significant challenge due to the limitations of traditional trial-and-error methods. This study proposes and validates a systematic predictive framework which integrates thermodynamic glass-forming region (GFR) calculation and a phase diagram approach for the Zn(PO 3 ) 2 –Ba(PO 3 ) 2 –Al(PO 3 ) 3 –BaF 2 quaternary system. Thermodynamic modeling effectively delineated the quaternary GFR with a high experimental overlap ratio of 83.7%, demonstrating its capability to navigate complex compositional boundaries. Furthermore, macroscopic physical properties including density, glass transition temperature and crystallization resistance, and local structural-dependent spectroscopic characteristics were accurately predicted (average deviation below 6.49%) based on congruently melting compound motifs. Based on high-throughput screening of the spectroscopic figure of merit, an optimized composition (20Zn(PO 3 ) 2 –34Ba(PO 3 ) 2 –30Al(PO 3 ) 3 –16BaF 2 ) was selected for fiber fabrication. The resulting Yb 3+ -doped fiber exhibited a competitive net gain of 5.47 dB/cm at 1064 nm. Under 976 nm pumping, efficient laser oscillation was achieved with a high signal-to-noise ratio of 50 dB and a low threshold of 11.8 mW. These results confirm that the phase-diagram-based methodology significantly accelerates the material development cycle, offering a robust framework for designing high-performance gain media for narrow-linewidth and ultrafast laser applications.