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

Abstract

Er3+-doped CdO–V2O5–ZnO–B2O3 (CVZB-Er) inverted glasses were synthesized by the melt-quenching method. X-ray diffraction (XRD) patterns showed an amorphous structure in all Er3+ doping ranges. This fact was verified by the line shape of Raman spectra, which revealed two broad vibrational bands attributed to V2O5 and B2O3 glass former species. The direct optical band gap (Egd) values were found around 2.74 eV, without tendency with Er3+ concentration. Under 980 nm laser excitation, the down-shifting emission spectra exhibited the featured near-infrared Er3+: 4I13/2 → 4I15/2 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 (2H11/2, 4S3/2) and 4F9/2 excited states to the 4I15/2 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 Ω2 = 6.43 × 10−20 cm2, Ω4 = 0.96 × 10−20 cm2 and Ω6 = 1.53 × 10−20 cm2 for the CVZB glass activated with 2.8 mol% of Er3+. Such values are close to those reported in other glass systems. Moreover, the radiative transitions arising from the 4I13/2 and 4S3/2, states to the 4I15/2 ground one presented radiative branching ratio (βR) values higher than 0.6, and total radiative transfer probabilities AT (4I13/2 →4I15/2) = 782.46 s−1 and AT (4S3/2 →4I15/2) = 10248.56 s−1. For the 4I13/2→4I15/2 emission transition, laser parameters such as the stimulated emission cross-section (σem(λ) = 1.57 × 10−20 cm2), gain bandwidth (σem(λ) × Δλem=9.3 × 10−26 cm3), optical gain (σem(λ) × τR=2.0 × 10−23 cm2s) and quantum yield (η=0.33) were calculated.