Impact of ytterbium on photoluminescence from the modifier in TeO₂–ZnO:Ho³⁺ glass

The effect of incorporation of Yb³⁺ ions in Ho³⁺ doped TeO₂–ZnO glass prepared by a melt quenching method is discussed. The amorphous nature of the prepared glass was confirmed by X-ray diffraction analysis. The optical absorption spectrum displayed several peaks, which correspond to the dopant ions embedded into the TeO₂–ZnO glass. The photoluminescence emission spectra measured upon excitation with a 325 nm He–Cd laser revealed a broad emission band of the modifier (ZnO) along with other peaks of the Ho³⁺ ions. A comparison of codoped glass emission with the singly Ho³⁺ doped system showed significant enhancement of the ZnO emissions while the Ho³⁺ peaks were reduced. This may be due to the energy transfer involved between the dopant ions and the glass modifier at an excitation wavelength of 325 nm. The energy transfer mechanism is discussed with a suitable energy level structure and the colour of the light emitted from the glass has been examined by calculating the corresponding colour coordinates.