FT-IRRS, UV–Vis–NIR absorption and green upconversion in Er3+ doped lead silicate glass

Abstract

Fourier transform infrared reflection spectroscopic (FT-IRRS), ultraviolet–visible–near infrared (UV–Vis–NIR) absorption and green upconversion fluorescence properties of an Er3+ ion doped high PbO (72.5 wt.%) content lead silicate glass have been studied at room temperature. FT-IRRS and UV–Vis–NIR absorption spectral band positions have been discussed quantitatively with theoretical calculation and covalent bonding characteristics of the glass respectively. NIR radiation upconversion into green fluorescence has been investigated by exciting at 979 nm. Two green upconverted bands with doublet characteristics originating from 4S3/2→4I15/2 and 2H11/2→4I15/2 transitions have been found to be centered at 550 (strong) and 530 (weak) nm respectively. These bands have been justified from the evaluation of the absorption, normal (down conversion) fluorescence and excitation spectra. The upconversion processes have been explained by the excited state absorption (ESA) and energy transfer (ET) mechanisms involving population of energy levels by multiphonon deexcitation and thermal effects. It is evident from IRRS studies that the upconversion phenomenon is expedited by the low multiphonon relaxation rate in lead silicate glass owing to its low phonon energy (990 cm−1) compared to that in silica glass (1122 cm−1).