Tb3+-Tb3+ cross-relaxation study under novel experimental technique: Simultaneous laser excitation at UV-Vis

Abstract

Tb³⁺ doped GeO₂-Na₂O glasses have been fabricated by conventional melt quenching technique using 0.3, 1, 3, and 5 %mol of terbium ions. The optical properties were studied by means of steady-state photoluminescence (excitation and emission spectra), and emission decay time. Under excitation of 355 nm and as the concentration of dopant increases, the glasses show an enhancement of the emission intensity from ⁵D₄ level accompanied by a decrease on the emission intensity from ⁵D₃ level. This phenomenon can be attributed to an energy transfer process that occurs through cross-relaxation mechanisms between Tb³⁺ ions. The aim of this study is to report an experimental technique to study the cross-relaxation of ⁵D₃ level decay curves of Tb³⁺ ions under simultaneous temporal and spatial pulsed excitation using UV and visible light (355 nm + 488 nm), allowing to limit the occurrence of cross-relaxation mechanisms and increase luminescent efficiency. Upon simultaneous UV + Vis excitation, the emission from ⁵D₃ level in enhanced, as the energy of the 488 nm pulse is increased. Additionally, the energy transfer efficiency between Tb³⁺ ions was analyzed with the Inokuti-Hirayama (IH) model, as function of the excitation pulse energy at 488 nm, keeping fixed the energy of the 355 nm pulse, determining a dipole-dipole interaction as the dominant interaction mechanism.

Keywords: Decay times; Energy transfer; Germanate glasses; Luminescence; Terbium.