Nd3+ doped magnesium zinc sulfophosphate glass: new candidate for up-conversion solid state laser host

Abstract

Phosphate based glasses with neodymium ions (Nd3+) doping are advantageous for high energy short pulse up−conversion (UC) solid−state laser applications. In this work, the magnesium zinc sulfophosphate glass systems with composition of (60−x)P2O5–20MgO–20ZnSO4−xNd2O3 (where x = 0.0, 0.5, 1.0, 1.5 and 2.0 mol%) were prepared via melt−quenching method. Structures of as−quenched samples were characterized at room temperature using Fourier-transform infrared spectrometer FTIR and Raman measurements. Thermogravimetry−differential thermal analyses (TG−DTA) confirmed the thermal stability (>100 °C) of selected glasses. Ultraviolet–visible near-infrared (UV–Vis–NIR) absorption and photoluminescence (PL) spectroscopy were used to evaluate the optical properties of the proposed glasses. Absorption spectra of glasses revealed thirteen characteristic bands in the range of 328–875 nm which were assigned to the ground state to various excited states transitions in Nd3+ ions. The reliability of the Judd−Ofelt (JO) evaluation was authenticated via the attainment of the very low value of root mean square deviation (0.18 × 1020 to 0.63 × 1020 cm2). The spectroscopic quality factors of glasses were enhanced from 1.51 to 2.07 with the increase in Nd3+ ions doping contents. Glass containing 1.5 mol% of Nd3+ ions displayed a slight reduction of Ω2 value, validating the improvement of symmetrical environment around Nd3+ ions in the glass network. Meanwhile, the observed enhancement in the Ω4 and Ω6 values with increasing Nd3+ ions content was ascribed to the improvement of glass viscosity and rigidity. The achieved green−yellowish PL band around 580 nm (emerged from 2G7/2 → 4I9/2 transition) exhibited large branching ratio (83–84%), indicating efficient lasing transition with improved emission cross−section (3.25–4.70 × 10−25 m2) in the glass system. Based on results, the proposed glass system was effective to be used in UC solid−state laser applications.