L. Boehm

Energy transfer between samarium and europium in phosphate glasses

Abstract A study of energy transfer from samarium to europium in phosphate glasses was performed for a range of donor and acceptor concentrations corresponding to a donor-acceptor distance of 13–24 A. The energy transfer probabilities were calculated. The mechanism of transfer was deduced by fitting the experimental decay curves to the theoretical curves obtained by Inokuti and Hiroyama. Theoretical transition probabilities based on Dexters formula were calculated. It was inferred that the energy is transferred by a dipole-quadrupole mechanism which is assisted by phonons. It was possible to indicate the path by which the transfer takes place.

Optical transitions of Sm3+ in oxide glasses

Eigenvectors of the 4f5 electronic configuration of Sm3+ were calculated in intermediate coupling, and used to obtain the reduced matrix elements U(λ). Absorption spectra of Sm3+ were recorded in phosphate, borate, germanate and tellurite glasses. The Judd-Ofelt Ωλs intensity parameters were then deduced from the measured oscillator strengths by least-squares fitting. Radiative transition probabilities and integrated cross-sections of stimulated emissions are obtained. Calculated branching ratios and decay lifetimes are compared with the experimental values.

Transition probabilities of europium(III) in zirconium and beryllium fluoride glasses, phosphate glass, and pentaphosphate crystals

Abstract Eigenvectors of Eu 3+ were obtained by a least-squares fitting procedure to the measured transitions from the two lowest J levels to a multitude of excited levels up to 41 000 cm −1 . The Judd-Ofelt parameters Ω t (t = 2, 4, 6) were obtained by comparison between the U (t) calculated from the eigenvectors, and the observed oscillator strengths. Radiative transition probabilities and branching ratios were evaluated for the excited states 5 D J (J = 0, 1, 2, 3) and 5 L 6 to 7 F J . The agreement between the calculated and observed lifetimes and branching ratios is better in oxide glasses than in the pentaphosphate crystal and fluoride glasses. This can be understood on the basis of the higher variety of sites and hence, better averaging.

Multiphonon relaxation of rare earth ions in borate, phosphate, germanate and tellurite glasses☆

Abstract Non-radiative multiphonon relaxation rates were obtained for excited electronic states in borate, phosphate, germanate and tellurite glasses. The rates were calculated from the intensities of fluorescence in the visible range of the spectrum, the measured radiative transitions and the decay times of fluorescence. A functional dependence was found between the relaxation rates and the energy gaps of the rare earth ion. It was shown that by changing the glass host from the borate to tellurite matrix, an increase in visible fluorescence was achieved. This was especially notable in Er 3+ , where the increase of fluorescence from germanate to tellurite was by a factor of 15.

Optical characteristics and intensity parameters of Sm3+ in GeO2, ternary germanate, and borate glasses

Abstract Absorption and fluorescence spectra of Sm3+ were measured in GeO2, ternary germanate, and borate glasses. From these the intensity parameters were calculated by use of the Judd-Ofelt formula. Visible emission and decay times from the4G5/2 level and its relative quantum efficiencies were measured The quantum efficiencies (QE) of the fluorescence in ternary germanate was higher by a factor of 20 than in GeO2, The small QE in GeO2, is explained by cross-relaxation between neighboring Sm3+ ions. The later process in hindered by the change in glass structure in the presence of modifier ions. A similar effect is observed in other glasses such as borate, where the addition of modifiers increases the QE of fluorescence.

Luminescence and nonradiative relaxation of Pb2+, Sn2+, Sb3+, and Bi3+ in oxide glasses

Abstract Absorption and fluorescence spectra of Sn 2+ and Sb 3+ in borax, phosphate, and germanate glasses were measured in the temperature range 87–295°K. Fluorescence decay times of these ions in borax glass at 87°K was a single exponent with τ ≈ 6–11 μsec. At 293°K, two decay times were resolved in the range of 50–2000 nsec. The nonexponential behavior is interpreted by the repopulation of the 3 P 1 level from the 3 P 0 level. The temperature dependence of fluorescence and the low values of quantum efficiencies of fluorescence are explained by means of the configurational coordinate diagram model.

Energy transfer between Bi3+ → Eu3+, Bi3+ → Sm3+ and UO2+2 → Eu3+ in oxide glasses

Abstract Probabilities and efficiencies of energy transfer from Bi3+ to Eu3+, Bi3+ to Sm3+ in borax and germanate glasses, and from UO2+2 to Eu3+ in phosphate glass were measured. Enhancement of acceptor fluorescence by two orders of magnitude was achieved as a result of energy transfer. From the decrease of donor fluorescence lifetime the energy transfer from UO3+2 to Eu3+ was found to be nonradiative.

Calculated Radiative and Nonradiative Transition Probabilities and Stimulated Cross-Sections of Selected Er3+ Lines in Oxide Glasses

Radiative transition probabilities for fluorescence bands extending from 0.523µ to 13µ of Er3+ in phosphate, germanate and tellurite glasses were calculated using the Judd-Ofelt approach. Multi-phonon relaxation rates from these levels were also calculated using the phenomenological parameters of multiphonon relaxation theory in glasses. Possible laser transitions of Er3+ in those glasses are discussed.