Spectroscopic properties of Nd3+-doped tungsten–tellurite glasses

Abstract

In this work, we investigate the spectroscopy properties of neodymium doped tungsten-tellurite glasses prepared in ambient and O 2-rich atmospheres. A conversion of TeO 4 to TeO 3 units was caused by the addition of Nd 3 þ into the glass, which was confirmed by absorption spectra and by Judd-Ofelt parameter behavior. The relaxation of the 4 F 3/2 level is dominated by radiative decay and cross-relaxation between Nd 3 þ and Nd 3 þ ions. The energy transfer from Nd 3 þ to the hydroxyl group is negligible when compared to the cross-relaxation. The luminescence quantum efficiency values of the 4 F 3/2 level decreases as the Nd 3 þ concentration increases, independently if determined by the Judd-Ofelt method or by the thermal lens technique. The observed reduction in the IR absorption associated to OH groups was not effective to improve the luminescence quantum efficiency.

High Nd3+→Yb3+ energy transfer efficiency in tungsten‐tellurite glass: A promising converter for solar cells

“…A linear dependence was observed for the Yb 3+ absorption (at 978 nm) vs concentration of Yb 3+ ions (not shown), indicating successful incorporation of Yb 3+ into the prepared glasses. A blue shift of the absorption edge is also observed, indicating that the addition of Yb 3+ caused a change in the glass structural units from TeO 4 (tbp=trigonal bi‐pyramid) to TeO 3 (tp=trigonal pyramid) . Similar changes were reported recently for Nd 3+ added to a TW host, promoting a slight reduction in its phonon energy (~942 cm −1 ) …”

“…The excitation and emission transitions, as well as the cross‐relaxations [between Nd 3+ ions (CR 1 ) and between Nd 3+ and Yb 3+ (CR 2 and CR 3 )] and multiphonon decay, are indicated by solid arrows, dashed arrows, and sinusoidal arrows, respectively. In our recent investigation of Nd 3+ ‐doped tungsten‐tellurite glasses, we observed that the cross‐relaxation rate ( W CR ) associated with the CR 1 energy transfer increased significantly as the Nd 3+ concentration increased . However, in this study, W CR1 is constant due the fixed Nd 3+ concentration in the co‐doped samples.…”

“…In our recent investigation of Nd 3+ -doped tungsten-tellurite glasses, we observed that the cross-relaxation rate (W CR ) associated with the CR 1 energy transfer increased significantly as the Nd 3+ concentration increased. 23 However, in this study, W CR1 is constant due the fixed Nd 3+ concentration in the co-doped samples. Exciting Nd 3+ at 808 nm induces a fast nonradiative relaxation from 4 F 5/2 , 2 H 9/2 to 4 F 3/2 , followed by radiative transitions (1339, 1066, and 898 nm) from the Nd 3+ metastable level to the 4 I J fundamental levels, along with the CR 1 and CR 2 energy transfers.…”

“…Also, the Nd 3+ concentration is the same in the co‐doped systems, so the ESA contribution is the same for all studied samples. For the 1Nd glass, the curve in the monolog plot is apparently linear; fitting it with a single exponential function resulted in an experimental lifetime of (115 ± 1) μs, which is shorter than the radiative lifetime calculated via Judd‐Ofelt theory (152 ± 4) μs . This difference among experimental and calculated lifetime is an indication of the presence of a nonradiative (CR 1 ) process between Nd 3+ ions.…”

“…Addition of 0.5 mol% of Yb 3+ to the 1Nd glass resulted in a reduction of 63% in the 4 F 3/2 level lifetime of Nd 3+ due to the energy transfer from Nd 3+ to Yb 3+ by CR 2 . Comparing the samples with different Yb 3+ concentrations showed a decrease in the Nd 3+ lifetime from 42 to 5 μs, which could be attributed to an efficient energy‐transfer process (CR 2 ) between Nd 3+ and Yb 3+ ; this is because CR 1 was kept constant (1.2 × 10 3 s −1 ) …”