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.