Erbium energy bridging upconversion mechanism studies on BAKL:Er3+/Yb3+ glass-ceramics and simultaneous enhancement of color purity of the green luminescence

Abstract

Borate oxyfluoride glasses are transparent in the infrared, ultraviolet and visible regions and represent an ideal host matrix for optically active dopants. Due to their lower phonon energies compared to a silicate glass matrix, non-radiative transitions are suppressed and high luminescence efficiency is expected. This work reports on a complete upconversion (UC) luminescence study of the optically active B₂O₃–Al₂O₃–KF–LiO (BAKL) glass-ceramics incorporated with Er³⁺/Yb³⁺ ions. The triclinic BAKL:Er³⁺/Yb³⁺ glass-ceramic (GC) phosphor was synthesized using the conventional melt-quenching technique and the subsequent heat treatment of the precursor glass. The successful synthesis of BAKL:Er³⁺/Yb³⁺ GCs was confirmed by X-ray diffraction, Fourier transform infra-red and differential thermal analysis measurements. The glasses were crystallized under controlled conditions, and the influence of phase composition (glass-to-crystalline phase ratio) on the wavelength and UC luminescence was thoroughly studied under 980 nm excitation. Interesting color tuning properties (white to intense green emission) of the sample were observed with laser pump power increment. The color tuning properties were explained using a new strategy i.e. the energy bridging mechanism between Er³⁺ ion clusters through an intermediate Yb³⁺ level. Moreover, their high color purity is well retained by varying the NIR excitation pump power densities and photometric characterization indicated the suitability in light emitting diodes and Er³⁺ doped fiber amplifier applications.