Up-conversion photoluminescence characteristics of Yb³⁺:Er³⁺:Tm³⁺ co-doped borosilicate glasses

Yb³⁺:Er³⁺:Tm³⁺co-doped borosilicate glasses are prepared. Their strong up-conversion photoluminescence spectra in a range from ultra-violet to near-infrared, which are excited by a 978-nm laser diode, are measured, and the mechanisms of energy transfer among Yb³⁺, Er³⁺ and Tm³⁺ ions are discussed. The results show that there is an unexpected wavelength at 900-nm emission from Yb³⁺ Stark splitting levels to pump Tm³⁺ ions and there exists an optimum pump power. The concentration of the Tm³⁺ dopant gives rise to a prominent effect on the intensity of visible and near-infrared emissions for the Yb³⁺:Er³⁺:Tm³⁺ co-doped borosilicate glasses.