Enhanced 1.5 μm emission of Er3+-doped multifunctional Bi2ZnOB2O6 microcrystals

Abstract

The efficiency of the 1.5 μm emission associated with the ⁴I_13/2 → ⁴I_15/2 transition of Er³⁺ ions of a series of Er³⁺ and Yb³⁺/Er³⁺-doped Bi₂ZnOB₂O₆ microcrystalline powders was investigated. Bi₂ZnOB₂O₆ is an excellent nonlinear optical material as well as a good host matrix for luminescent rare-earth ions. The investigated powders were synthesized by means of the modified Pechini method and their orthorhombic structure with Pba2 space group were confirmed by XRD measurements. The vibrational properties of Bi₂ZnOB₂O₆:Yb³⁺/Er³⁺ were studied using μ-Raman spectroscopy. The low phonon energy of the Bi₂ZnOB₂O₆ matrix allows effective phonon assisted energy transfer between rare-earth ions and/or multiphonon relaxation processes of rare-earth ions. It was revealed that the intensity of the 1.5 μm emission under 980 nm excitation increased with increasing Er³⁺ concentration (from 0.5 to 3.0 at%) for Bi₂ZnOB₂O₆:Er³⁺, while for co-doped Bi₂ZnOB₂O₆:Yb³⁺/Er³⁺ systems a significant increase in this emission was observed for the optimal Yb³⁺/Er³⁺ concentration (1.5/0.5 at%). Moreover, the intensity of the 1.5 μm emission decreases with increasing temperature for all investigated samples. Additionally, Bi₂ZnOB₂O₆:Yb³⁺/Er³⁺ powders exhibit effective up-conversion luminescence in the visible range under 980 nm excitation. In the up-conversion spectra of Bi₂ZnOB₂O₆:Yb³⁺/Er³⁺ powders, the bands corresponding to green and red emission of Er³⁺ ions (²H_11/2 → ⁴I_15/2/⁴S_3/2 → ⁴I_15/2 and ⁴F_9/2 → ⁴I_15/2 transitions, respectively), as well as the bands at about 487 nm (blue emission) associated with second harmonic generation produced by the Bi₂ZnOB₂O₆ matrix were detected. The results indicate a potential for application of Bi₂ZnOB₂O₆:Yb³⁺/Er³⁺ powders as effective multifunctional new-generation photonic materials.