Effect of mixed TeO2–B2O3 glass former in Ho3+/Yb3+-doped glass system: Raman spectroscopy, Judd-Ofelt and luminescence investigations

Abstract

In this work, glass with composition (75-x)B2O3-xTeO2-11Bi2O3–10Li2O-1Ho2O3-3Yb2O3 (x = 10–60 mol%) were synthesized using the melt quenching technique to investigate the effect of mixed glass former between TeO2 and B2O3 on the spectroscopic properties of glass. The Raman Spectroscopy has revealed a structural depolymerization undergone by the glasses with a sudden increment at x = 30 mol% that might arise from structural competition between TeO2 and B2O3. Optical absorption spectra have revealed 9 absorption peaks corresponding to Ho3+ ion transitions while one peak belongs to Yb3+ ion transition. The bonding parameter signifies the glasses are ionic in nature. The oscillator strength and Judd-Ofelt parameter Ω2,4,6 have reduced against increment of TeO2 concentration indicated a low asymmetry and low rigidity except for x = 30 mol% that may be due to strong interaction between TeO2 and B2O3. The radiative properties such as spontaneous emission probability, branching ratio, radiative lifetime and stimulated emission cross-section have showcased the glass potential for laser application. The luminescence spectra of studied glasses upon 450 nm excitation have disclosed two main emission bands which are 530 nm and 642 nm that corresponding to 5F4–5I8 and 5F5–5I8, of Ho3+ respectively whilst an extra emission recorded at 738 nm was ascribed to 5F4–5I7 of Ho3+ due to energy transfer process from Yb3+ to Ho3+. The emission intensity of the samples has enhanced with the TeO2 addition due to reduction of phonon energy. CIE 1931 diagram has shown a greener emission colour of glass samples over TeO2 addition.