Fabrication and Laser Amplification Behavior of Yb3+/Al3+ Co-Doped Photonic Crystal Fiber

Yb³⁺/Al³⁺ co-doped silica glass with the composition of 0.1Yb₂O₃-1Al₂O₃-98.9SiO₂ was prepared by sol–gel method combined with high-temperature sintering. Using this glass as active core, a photonic crystal fiber (PCF) with 105- $\mu \text{m}$ core was fabricated by the stack-capillary-draw technology. The refractive index fluctuation of this core rod is as low as $2 \times 10^{\mathrm {\mathbf {-4}}}$ , implying that highly homogenous silica preform can be realized in this method. Furthermore, this PCF achieved a maximum amplified power of 255 W, with a slope efficiency of 65.7%. It indicates that Yb³⁺-doped silica preform prepared by the sol–gel method can be employed in the field of high-power laser.