Luminescence and study of channels for cross-relaxation dependent on the concentration of Sm3+ under simultaneous UV-IR excitation in tellurite-germanate glasses

Abstract

A spectroscopic evaluation of Sm3+ doped TeO2-GeO2-ZnO glasses (0.5, 1.0, 3.0 and 5.0%) was carried with aim to determinate the dominant process in the cross-relaxation mechanism at high and low concentrations of Sm3. A new experimental spectroscopic technique is proposed, based on the analysis of the time evolution of the 600 m emission, corresponding to the 4G5/2 → 6H7/2 transition, obtained under spatial and temporal simultaneous excitation at 355 nm and into the infrared (950, 1085 1236, 1380 nm). It was possible to determine that at low Sm3+ content the dominant channel for cross relaxation is 4G5/2 + 6H5/2 → 6F5/2 + 6F11/2 and at high concentrations are: 4G5/2 + 6H5/2 → 6F7/2 + 6F9/2, 4G5/2 + 6H5/2 → 6F9/2 + 6F7/2, 4G5/2 + 6H5/2 → 6F11/2 + 6F5/2, and the least contributor one being 4G5/2 + 6H5/2 → 6F5/2 + 6F11/2. It is reported the optical absorption and Raman spectroscopies, photoluminescence spectra and decay time profiles as a function of Sm3+ concentration. Emission spectra measurements indicated that concentration quenching is active in the samples, being 1.0 mol% the optimum concentration for luminescence of Sm3+ ions. The decay time of 4G5/2 level upon 403 nm excitation, at 0.5% of Sm3+, presents a decay curve single exponential, however, when the concentration increases, the time decay reduces and becomes non-exponential. The Inokuti-Hirayama model was used to infer that an electric dipole-dipole mechanism is the dominant interaction in the energy transfer process between Sm3+-Sm3+ ions.