Energy transfer upconversion in Er³⁺-Tm³⁺ codoped sodium silicate glass

Er³⁺/Tm³⁺ doped and codoped Na₂O-SiO₂-ZnO (NSZO) glasses were prepared by the conventional melt-quenching method. The amorphous nature of the prepared glasses was confirmed by the X-ray diffraction analysis. The optical absorption spectrum displayed several peaks, which correspond to Er³⁺ and Tm³⁺ dopant ions embedded into the NSZO glass. Both dopants experienced upconversion emission under 980 nm excitation. Efficient energy transfer from Er³⁺ to Tm³⁺ was observed in the co-doped samples to enhance the near infrared emission of the Tm³⁺ ions.