Optical Properties of Rare‐Earth Ions in Lead Germanate Glasses

Abstract

Glasses of composition (x − 1)PbOؒ(100 − x)GeO 2 ؒ1Ln 2 O 3 , with x = 30 mol% (Ln = Nd, Eu, Er), 40 mol% (Ln = Pr, Nd, Sm, Eu, Dy, Ho, Er, Tm), and 50 mol% (Ln = Eu, Er), have been prepared by quenching the oxidic melts. From the optical absorption and emission spectra in the ultravioletvisible-near-infrared (UV-VIS-NIR) region, the intensity parameters, spontaneous emission probabilities, branching ratios, radiative lifetimes, and, for selected NIR transitions, peak stimulated emission cross sections have been obtained. The trends observed in the intensity parameters have been discussed, as a function of the number of f electrons as well as a function of the lead content. As the amount of lead increases, the covalency of the Ln−O bond increases, the symmetry of the rare-earth site increases, and the dopant site distribution narrows. The peak stimulated emission cross sections rank among the highest found for oxide glasses.

Infrared-to-visible upconversion of Er^3+ ions in GeO_2–PbO–Nb_2O_5 glasses

“…If one employs a least-squares fitting of calculated and experimental oscillator strengths, the Judd-Ofelt parameters obtained for this glass are ⍀ 2 ϭ 6.64 ϫ 10 Ϫ20 cm 2 , ⍀ 4 ϭ 1.52 ϫ 10 Ϫ20 cm 2 , and ⍀ 6 ϭ 0.97 ϫ 10 Ϫ20 cm 2 , with a root-mean-square deviation equal to 2.62 ϫ 10 Ϫ7 . These values are in agreement with those previously reported in binary lead-germanate glasses 9 and in leadtellurium-germanate-based glasses. 21 The radiative transition probabilities for all excited levels of Er 3ϩ can be calculated by using the Judd-Ofelt parameters.…”

“…5,6 Among oxide glasses, lead-germanate-based glasses combine high mechanical strength, high chemical durability, and temperature stability with good transmission in the IR region 7 up to 5.5 m, which make them promising materials for technological applications such as new lasing materials, upconverting phosphors, and optical waveguides. [8][9][10][11][12] These glasses have smaller maximum vibrational frequencies than those shown by silicate, phosphate, and borate glasses. 7,8 The reduced phonon energy increases the quantum efficiency of luminescence from excited states of rare-earth ions and the upconversion efficiency.…”

Optical properties of Tm3+ ions in alkali germanate glass

“…Overall, the Judd-Ofelt parameters shown in table 2 for Tm:germanate glasses show the trend Ω 2 > Ω 4 > Ω 6. The exception seems to be the study by Wachtler [12], where the Ω 4 is unusually low. The most likely reason for this is a poor fit to the experimental absorption data.…”

“…In practice, the Judd-Ofelt theory has been used with great success to determine branching rations and lifetimes in a great number of ion-host systems. The set of phenomenological parameters, Ω λ (λ = 2, 4, 6), determined by fitting the experimental absorption, in a least squares difference sum, with the Judd-Ofelt expression are shown in table 2 and are compared with the parameters obtained in five other studies [4,6,7,12,13]. Overall, the Judd-Ofelt parameters shown in table 2 for Tm:germanate glasses show the trend Ω 2 > Ω 4 > Ω 6.…”

“…To combat the deleterious effects of nonradiative decay, Tm:germanate glass is investigated. There are very few studies of the optical properties of Tm in germanate glass [3][4][5][6][7][8][9][10][11][12][13], and those in recent years concentrate on lead germanates [8-10, 12,13]. This study concentrates on alkali germinates.…”