Spectroscopic investigations of Nd3+ doped gadolinium calcium silica borate glasses for the NIR emission at 1059 nm

Abstract

The Nd3+-doped gadolinium calcium silica borate (BSGdCaNd) glasses of composition (55-x) B2O3 - 10 SiO2 - 25 Gd2O3 -10 CaO -x Nd2O3, where x = 0.0, 0.05, 0.5, 1.0, 1.5, 2.0 and 2.5 mol %, have been prepared by conventional melt quenching technique and are characterized through structural, thermal, absorption, emission and decay time measurements. Based on the Judd-Ofelt intensity parameters and radiative properties were determined from the absorption spectrum. The emission spectra recorded for BSGdCaNd glasses gives three emission transitions 4F3/2 → 4I9/2 (903 nm), 4F3/2 → 4I11/2 (1059 nm) and 4F3/2 → 4I13/2 (1334 nm) for which effective bandwidths (Δλeff) and stimulated emission cross-section (σ(λp)) are evaluated. Branching ratios (βR) measured for BSGdCaNd0.5 glass show that 4F3/2 → 4I11/2 transition is quite suitable for lasing applications. The intensity of emission spectra increases with increase in the concentration of Nd3+ ion up to 1.0 mol% and beyond that concentration, quenching is observed. The decay from 4F3/2 level is found to be non-exponential nature for concentrations of Nd3+ ions. The non-exponential curve has been fitted to the Inokuti-Hirayama model to understand the nature of energy transfer process. Hence, the high emission cross-section (1.39 × 10−20 cm2), branching ratio (0.58) and long lifetime (342 μs) indicate that the BSGdCaNd0.5 glass system could be considered as a good candidate for strong NIR lasers at 1059 nm.