Broadband 2 µm fluorescence and energy transfer process in Tm³⁺ doped germanosilicate glass

Glass with the composition of SiO₂-GeO₂-CaCO₃-Li₂CO₃-Nb₂O₅-BaO-Tm₂O₃ has been prepared and its characteristic temperatures have been measured. ΔT (155 °C) of the glass indicates it has good thermal stability. A broadband emission spectrum around 2 µm with full-width at half-maximum close to 237 nm has been obtained, which suggests this germanosilicate glass is a competitive candidate for the ultrashort pulse generation as few broadband emission realized by Tm³⁺ single-doping. The calculated maximum of absorption cross section and emission cross section of the transition Tm³⁺:³F₄→³H₆ was 3.31×10⁻²¹ cm² at 1654 nm and 6.88×10⁻²¹ cm² at 1870 nm, respectively. Besides, the energy transfer mechanism of 2 µm fluorescence behaviors was analyzed theoretically and quantitatively. The energy transfer coefficient C_D-A of cross relaxation process of Tm³⁺ ions was 10.9×10⁻⁴⁰ cm⁶/s in SGT glass. These results indicate that the prepared glass may have promising application in 2 µm fluorescence.