Investigations on the photoluminescence of the iron and cobalt doped fluoride-containing phosphate-based glasses and its defects-related nature

Abstract

The influence of doping iron and cobalt ions on the formation of defects in the fluoride-containing phosphate-based glasses was studied comprehensively by means of analyzing the absorption and photoluminescence (PL) spectra as well as the electron spin resonance (ESR) spectra. The absorption and ESR spectra show that the defects, including phosphate-related oxygen hole center (POHC), oxygen-related hole centers (OHC), Fe3+, Co2+, PO3-EC, PO4-EC and fluorine-related non-paramagnetic color (FD) centers were formed during the glass preparation process. In addition, the analysis on the PL and absorption as well as excitation (PLE) spectra indicate that PO4-EC and OHC defects which have large absorption in the UV region result in the emission band peaking at 780 nm under the excitation at 351 nm for the cobalt doped (2ω absorptive) glass. Addition of small quantities of iron causes the effectively intense absorption towards the 1ω wavelength (1053 nm) due to the presence of Fe2+, but also a distinctively observed red-shift of the UV absorption edge was dominated by the charge-transfer transition of the existence of Fe3+. The experimental results demonstrate that Fe3+ suppress the formation of FD defects in the glasses, while promotes the formation of POHC defects. Besides, introduction of Co2+ inhibits the formation of POHC and PO4-EC defects, and Fe2+ promotes forming of POHC defects.