Optical and spectroscopic properties of rare earth-doped (80−x)TeO2-xGeO2-10Nb2O5-10K2O glasses

► Estimation of the Er3+:1.5 nm PL lifetime by ACS and Judd-Ofelt methods. ► ACS method as a simpler approach to estimate de lifetime of rare-earths transitions to ground state. ► Increase of Er3+:1.5 nm PL lifetime, FWHM and Ω2 parameter related with the increase of germanium content. ► FWHM of 74 nm registered for a tellurite rich glass composition doped with 5% ErO1.5. ► Study of the up-conversion luminescence of Er, Yb and/or Tm doped germanotellurite glasses.