Spectroscopic properties of Tm3+-Ho3+ codoped SiO2-Al2O3-CaO-SrO glasses

Tm3+-Ho3+ codoped 50SiO2-10Al2O3-25CaO-15SrO glasses with good thermal stability are prepared by a melt-quenching method. Efficient emission of Ho3+:5I7 is observed upon excitation with an 800 nm laser. The sample doped with 1 mol% Tm2O3 and 0.1 mol% Ho2O3 presents a broadband spectrum with a full width at half-maximum of 345 nm. The sample doped with 1 mol% Tm2O3 and 0.7 mol% Ho2O3 has the maximum emission intensity of Ho:5I7 to5I8. With increased Ho2O3 content, the fluorescence intensity ratio of emission from Ho:5I7 to that from Tm:3F4 linearly increases. The emission cross-section and energy-transfer efficiency are also calculated. The maximum emission cross-section of the transition from Ho:5I7 to 5I8 is 3.72×10−21 cm2 at 2065 nm. When the sample is doped with 1 mol% Tm2O3 and 1 mol% Ho2O3, the transfer efficiency from Tm3+ to Ho3+ is 0.954. The emission cross-section, energy-transfer constants, and fluorescence efficiency in 50SiO2-10Al2O3-25CaO-15SrO glass are larger than those in silicate glasses without alkali ions, indicating that 50SiO2-10Al2O3-25CaO-15SrO glass is a favorable glass host for 2 μm lasers.