Fig. 1. Flow chart of fabrication of extra-large-core active fiber based on glass phase-separation technique

Fig. 2. Property characterization of Yb3+ doped silica glass rod. (a) Photograph of sintered silica rod; (b) absorption spectrum; (c) FTIR spectrum; (d) XRD spectrum

Fig. 3. Refractive index profile of Yb3+ doped fiber (inset: sectional view of Yb3+ doped fiber)

Fig. 4. (a) Schematic of Yb3+ doped all-fiber MOPA test system; (b) slope efficiency of Yb3+ doped double-clad fiber laser; (c) spectrum of Yb3+ doped fiber laser