Energy transfer induced enhancement in NIR luminescence characteristics of Yb3+/Er3+ co-doped sodium zinc bismuth fluorophosphate glasses

Abstract

The results pertaining to the energy transfer-based photoluminescence characteristics of Er3+-doped and Yb3+/Er3+ co-doped NaF–ZnO–BiF3–NH4H2PO4 (NZBFP) glasses prepared through melt-quench technique were demonstrated here. By applying McCumber's theory, the absorption, stimulated emission cross-sections and optical gain have been estimated for Yb3+ (0.97 μm) and Er3+ (1.54 μm) ions. Yb3+-doped glass exhibited a sharp emission at 979 nm at 808 nm excitation while Er3+-doped glass displayed a broad NIR emission band at/around 1545 nm for 980 nm excitation. The presence of Yb3+ absorption band along with the Er3+ absorption bands in the co-doped glass suggests the energy transfer (ET) possibility within these ions. On pumping Er3+-doped &yYb3+/Er3+ co-doped NZBFP glasses with 980 nm Laser Diode, a broad Er3+ emission at 1545 nm attributed to 4I13/2 → 4I15/2 is observed in the NIR region. The increasing of Yb3+concentration with respect to Er3+ (fixed to 1 mol%) in co-doped glasses have resulted in enhancement of Er3+ NIR emission because of the resonant energy transfer (ET) process from Yb3+→Er3+. The energy transfer (ET) mechanism has been illustrated from the spectral overlap of Yb3+ emission and Er3+ absorption, Er3+ decay lifetime curves, and partial energy level diagram. Further, the nature of interaction responsible for the energy transfer process (ET) has been explained using Forster-Dexter theory and I–H fitting. In addition, the suitability of the present synthesized fluorophosphate glasses for optical amplifier and NIR laser applications were explored in terms of optical amplification and gain parameters, like effective band-width (Δλeff), stimulated emission cross-section (σe), optical gain (G), and gain bandwidth (ΔG).