Effect of AlPO4 join concentration on optical properties and radiation hardening performance of Yb-doped Al2O3-P2O5-SiO2 glass

Abstract

A series of Yb-doped silica glasses containing equimolar amounts of P2O5 and Al2O3 were prepared using a sol-gel method combined with high-temperature sintering. Raman spectroscopy confirmed the formation of AlPO4 join with a P/Al ratio of 1. However, for a P/Al ratio slightly larger than 1, both the AlPO4 join and P=O bond are formed. Based on the absorption, emission spectra, and electron paramagnetic resonance measurements, it was determined that the increase of the AlPO4 join concentration in Yb-doped silica glass leads to (i) a decrease in the refractive index with a factor of 1.1005 × 10-4 (which allows for a low numerical aperture facilitating single-mode laser), (ii) the sustained spectroscopic properties of Yb3+, (iii) a decrease in Yb cluster concentration, and (iv) an improved radiation hardening performance (beneficial to high-power space lasers). These results suggest that Yb-doped Al2O3-P2O5-SiO2 glass with an appropriate concentration of AlPO4 join has potential applications in high-power space fiber lasers.