Yb

Composite optical fibers with Yb3+ doped crystals embedded in glass matrices combine the benefits of crystalline and glassy phases for photonic applications. This work demonstrates the feasibility of preparing composite fibers within glass systems. YbPO4 crystals were incorporated into silica via solution doping of the soot layer during MCVD, followed by collapse and fiber drawing. Electron and Raman microscopy confirmed the survival of ~100 nm crystals after processing up to 2100 °C. Another fiber was prepared by embedding LiNbO3:Yb3+ crystals in phosphate glass using direct doping method. Both fibers demonstrate the potential of post-treatment-free, crystal-in-glass fibers for laser applications.