Modification of Strontium Oxide Concentration Stimulated Optical Properties of Er3+/Gd3+/Yb3+ Tri-doped Phosphate Glass

Abstract

Aseries of Er³⁺, Gd³⁺ and Yb³⁺ tri-doped phosphate glasses with compositions (48.5 x)P2O₅–30Li₂O– 20ZnO– (x)SrO, where 0 ≤ x ≤ 5 are prepared by melt quenching technique and their spectroscopic characterizations were made. The XRD patterns shows a broad peak which means the nature of the glass is amorphous. Glass samples are characterized via FTIR to examine the SrO concentration dependent structural properties. FTIR spectra revealed broad absorption bands (weak and strong) in wavenumber range of 1400 to 400 cm−1. Thermal properties, including glass transition temperature (Tg), crystallization temperature (T_c), and crystal melting temperature (T_m) are obtained using DTA. The UV-Vis-NIR absorption spectra are recorded in the range of 200-800 nm. Using the UV absorption edge, the values of optical band gap energy (E_opt) and the Urbach energy (∆E) are evaluated. It is demonstrated that SrO plays the role as an intermediate of glass formation and transforms the role to network-former or glass modifier depending on composition. The role of SrO in influencing the optical responses are analyzed and discussed. It is suggested that SrO contents assisted modification in the structure and absorption behaviour is attributed to the relaxing selection rules for forbidden transitions as well as reduction in the multi-phonon relaxation rate. Meanwhile, the observed optical improvements suggest that these glass compositions are potential for development of phosphate glass based efficient solid-state laser