Up-conversion and down-shifting emission traits of Er3+-doped CdO–V2O5–ZnO–B2O3 novel inverted glasses for photonic applications

Er 3+ -doped CdO–V 2 O 5 –ZnO–B 2 O 3 (CVZB-Er) inverted glasses were synthesized by the melt-quenching method. X-ray diffraction (XRD) patterns showed an amorphous structure in all Er 3+ doping ranges. This fact was verified by the line shape of Raman spectra , which revealed two broad vibrational bands attributed to V 2 O 5 and B 2 O 3 glass former species. The direct optical band gap ( E g d ) values were found around 2.74 eV, without tendency with Er 3+ concentration. Under 980 nm laser excitation, the down-shifting emission spectra exhibited the featured near-infrared Er 3+ : 4 I 13/2 → 4 I 15/2 emission band. Meanwhile, the upconverting (UC) emission spectra , with color purities up to 97 %, displayed the well-known green and red emission bands related to relaxations from the ( 2 H 11/2 , 4 S 3/2 ) and 4 F 9/2 excited states to the 4 I 15/2 ground one, respectively. This process is dominated by a linear decay mechanism, as revealed by the dependence of the intensity versus the excitation laser power. The Judd-Ofelt (JO) parameters, obtained by the least-square method from the experimental and calculated oscillator strengths , resulted in Ω 2 = 6.43 × 10 −20 cm 2 , Ω 4 = 0.96 × 10 −20 cm 2 and Ω 6 = 1.53 × 10 −20 cm 2 for the CVZB glass activated with 2.8 mol% of Er 3+ . Such values are close to those reported in other glass systems. Moreover, the radiative transitions arising from the 4 I 13/2 and 4 S 3/2 , states to the 4 I 15/2 ground one presented radiative branching ratio ( β R ) values higher than 0.6, and total radiative transfer probabilities A T ( 4 I 13/2 → 4 I 15/2 ) = 782.46 s −1 and A T ( 4 S 3/2 → 4 I 15/2 ) = 10248.56 s −1 . For the 4 I 13/2 → 4 I 15/2 emission transition, laser parameters such as the stimulated emission cross-section (σ em (λ) = 1.57 × 10 −20 cm 2 ), gain bandwidth (σ em (λ) × Δλ em =9.3 × 10 −26 cm 3 ), optical gain (σ em (λ) × τ R =2.0 × 10 −23 cm 2 s) and quantum yield (η=0.33) were calculated.