Energy transfer between localized and delocalized states rare-earth doped chalcogenide glasses

De Camargo, A.S., Lima, S.M., Catunda, T., Nunes, L.A.de Oliveira and Hewak, D. (2001) Energy transfer between localized and delocalized states rare-earth doped chalcogenide glasses. XXIV Encontro Nacional de Fisica da Material Condensada, Sao Lourenco, Brazil. 14 - 18 May 2001.

Abstract

Chalcogenide glasses are interesting materials due to their high nonlinearity, low phonon energies and consequent low non-radiative decay rate of rare-earth (RE) excited states and wide optical transparency window. These properties make them promising photonic materials for mid infrared applications. They can be classified as semiconductors with energy gap typically ~2eV, much narrower than insulating host materials (for YAG, E_gap ~6eV). Therefore, the RE doped 4f-shell transitions overlap with the optical transition of the host glass. The energy transfer process from the host glass to the RE ion (a delocalized to localized state transition) is attributed by intrinsic defects states in the glass. In this work, we performed conventional spectroscopic (absorption, luminescence and excitation, at 5K and 300K) and Thermal Lens (TL) measurements in Nd³⁺ doped gallium lanthanum sulfide (GLS) glasses. The TL measurements were performed with excitation energy bellow the band gap energy (2.6eV, λ ~500nm) and at the weak absorption tail (WAT). From WAT measurements (λ = 502, 514 and 528nm) we obtained ~40% for the probability of energy transfer from host to the ion. Pumping in resonance with the near infrared Nd³⁺ lines (λ = 814 and 891nm) we obtained the Nd³⁺ ion fluorescence quantum efficiency ~100%. However, at λ ~596nm we observed a very asymmetric TL lineshape indicating energy transfer from the ion to the host for λ < 590nm (the high energy side of the line).

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Contributors

Author: D. Hewak

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