Spectroscopic and laser properties of Al-P co-doped Yb silica fiber core-glass rod and large mode area fiber prepared by sol-gel method

Abstract

A large-size (empty set5 mm) Yb3+-doped silica fiber core-glass rod with an Al-P co-doped composition: 0.035Yb(2)O(3)-1.0Al(2)O(3)-1.0P(2)O(5)-97.965SiO(2) (mol%) was prepared by the sol-gel method combined with high-temperature melting technology. We successfully solved the doping homogeneity problem caused by the volatility of P2O5. The doping homogeneity of the glass rod was very high with the maximum refractive index fluctuation Delta n < 2 x 10(-4). The refractive index of the glass rod was very low because of the equimolar amounts of Al and P co-doping, which yielded an AlPO4 structure. A large-mode-area single cladding fiber (LMA SCF) and photonic crystal fiber (LMA PCF) with core diameters of 35 and 50 mu m, respectively, were drawn from this glass rod. Owing to the low refractive index of the core-glass rod and the corresponding low numerical aperture (NA, 0.033) of the core, the LMA SCF exhibited a high laser beam brightness with M-2 = 1.3-1.4. The LMA PCF exhibited the maximum output power, which was limited by the available pumping power, of 46 W and the slope efficiency of 61%. (C)2015 Optical Society of America