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Multiphonon Absorption and Photon Avalanche Criterion in Erbium Doped Materials

100%

Auzel F.

Acta Physica Polonica A

1996

vol. 90

issue 1

7-19

The photon avalanche effect has been recently observed at room temperature in erbium doped fluoride glasses and crystals, in a particularly clear way, displaying simultaneously all the typical features of this effect: (i) existence of a threshold for transmission at the excitation wavelength, (ii) up-conversion excitation threshold, (iii) long delay for threshold establishment. Analysing the first step of the avalanche effect as an anti-Stokes multiphonon absorption, it can be shown why this effect is so clearly observed at room temperature in our erbium studies. Our results are compared with other cases of avalanche, with cases which have been called "looping effects" and "quasi-avalanche" ones.

Comparison Between Standard and Modified Judd-Ofelt Theories in a Pr^{3+}-Doped Fluoride Glass

63%

Goldner P., Auzel F.

Acta Physica Polonica A

1996

vol. 90

issue 1

191-196

A method which takes into account normalized oscillator strengths is detailed for the calculation of parameters in Judd-Ofelt theory (B.R. Judd, Phys. Rev. 127, 750 (1962), G.S. Ofelt, J. Chem. Phys. 37, 511 (1962)). In the case of a Pr^{3+} -doped fluorozirconate glass, the Judd-Ofelt parameters obtained in this way do not depend strongly on the transitions included in the fit. Particularly, it is no longer necessary to exclude the ^{3}H_{4} → ^{3}P_{2} transition from the analysis. Three modified theories (F. Auzel, S. Hubert, P. Delamoye, J. Lumin. 26, 251 (1982), A.A. Kornienko, A.A. Kaminskii, E.B. Dunina, Phys. Status Solidi B 157, 267 (1990)) are also considered but do not improve the calculated intensities when the energy of the 5d level is set to its experimentally determined value. Finally, in connection with 1.3 μ amplification, the 1.3 μ reabsorption (^{1}G_{4} → ^{1}D_{2}) oscillator strength is computed from the various models as well as the 1.3 μ emission branching ratio (^{1}G_{4} → ^{3}H_{5}/^{1}G_{4} → ^{3}H_{6}). The best agreement with experiment is obtained with the standard Judd-Ofelt theory.

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2 Acta Physica Polonica A

2 1996

2 Auzel F.

1 Goldner P.

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Multiphonon Absorption and Photon Avalanche Criterion in Erbium Doped Materials

Comparison Between Standard and Modified Judd-Ofelt Theories in a Pr^{3+}-Doped Fluoride Glass