Spectroscopic properties of Tm3+/Al3+ co-doped sol–gel silica glass

Abstract Tm 3+ /Al 3+ co-doped silica glass was prepared by sol–gel method combined with high temperature sintering. Glasses with compositions of x Tm 2 O 3 –15 x Al 2 O 3 –(100 − 16 x ) SiO 2 (in mol%, x = 0.1, 0.3, 0.5, 0.8 and 1.0) were prepared. The high thulium doped silica glass was realized. Their spectroscopic parameters were calculated and analyzed by Judd–Ofelt theory. Large absorption cross section (4.65 × 10 −21 cm 2 at 1668 nm) and stimulated emission cross section (6.00 × 10 −21 cm 2 at 1812 nm), as well as low hydroxyl content (0.180 cm −1 ), long fluorescence lifetime (834 μs at 1800 nm), large σ em × τ rad (30.05 × 10 −21 cm 2 ms) and large relative intensity ratio of the 1.8 μm ( 3 F 4 → 3 H 6 ) to 1.46 ( 3 H 4 → 3 F 4 ) emissions (90.33) are achieved in this Tm 3+ /Al 3+ co-doped silica glasses. According to emission characteristics, the optimum thulium doping concentration is around 0.8 mol%. The cross relaxation (CR) between ground and excited states of Tm 3+ ions was used to explain the optimum thulium doping concentration. These results suggest that the sol–gel method is an effective way to prepare Tm 3+ doped silica glass with high Tm 3+ doping and prospective spectroscopic properties.