Upconversion fluorescence in Er 3+-doped Na 2O–GeO 2 glasses

Abstract

Electron spin resonance (ESR) and upconversion fluorescence spectra have been investigated for Er 3+-doped Na 2O–GeO 2 glasses with molar compositions of xNa 2O · (100 − x)GeO 2 · 0.7Er 2O 3 prepared by the melt quenching method. The g-value for Er 3+ derived from ESR spectrum and both the peak position and the integrated intensity of upconversion fluorescence spectra changed in the so-called germanate anomaly region of the glass. The upconversion fluorescence intensity correlated to the electron–phonon coupling strength.