Upconversion luminescence and energy transfer in the fluorophosphate glasses with low phosphate content doped with Tm3+ and Yb3+ions

• Published in: Journal of non-crystalline solids. X 2021-09, Vol.11-12, p.100065, Article 100065
• Main Authors: Kolobkova, Elena, Grabtchikov, Alexander, Khodasevich, Inna
• Format: Article
• Language: English
• Subjects: Cooperative energy transfer; Cross-relaxation; Fluorophosphates glass; Tm3+ ions; Upconversion luminescence; Yb-Yb dimers
• ISSN: 2590-1591; 2590-1591
• DOI: 10.1016/j.nocx.2021.100065

We report an experimental observation of the upconversion in fluorophosphate glasses doped with different concentrations of Tm3+ ions (from 1020 to 1015 ion/cm3) and a constant content of Yb3+ ions (1021 ion/cm3) when pumped by a diode laser with a wavelength of 975 nm with a change in the pumping power density from 2.0 to 14.5 kW/cm2. Possible mechanisms of population of the upper 1D2, 2G4 and 3F2,3 states of Tm3+ ions were discussed depending on their concentration. The role of cross-relaxation processes in the population of the upper excited levels is considered. A change in the values of n-parameter of the luminescence at 475 nm (1G4) from 3 to 2 and high upconversion at low Tm3+ ions concentrations (about 1018-1015 ion/cm3) were attributed to the cooperative energy transfer from Yb-Yb* dimers. It was found that Tm3+/Yb3+ co-doped fluorophosphate glasses could be promising as up-converting materials. •The concentration dependence of the UC luminescence of Tm3+/Yb3+ co-doped fluorophosphate glasses was studied.•Mechanisms of population of the state 2D1,3F2,3,1G4 and 1P0 of Tm3 + ions were discussed depending on their concentration.•The cooperative energy transfer from Yb-Yb* dimmers led to the high upconversion at low Tm3+ ions concentrations.