Excitation and luminescence of rare earth-doped lead phosphate glasses
J. Pisarska
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M. Sotys
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L. Z_ ur
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W. A. Pisarski
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C. K. Jayasankar
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C. K. Jayasankar Department of Physics, Sri Venkateswara University
, Tirupati 517 502,
India
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J. Pisarska (&) M. Sotys L. Z_ur W. A. Pisarski Institute of Chemistry, University of Silesia
, Szkolna 9, 40-007 Katowice,
Poland
Excitation and luminescence properties of Eu3?, Tb3? and Er3? ions in lead phosphate glasses have been studied. From excitation spectra of Eu3? ions, the electron-phonon coupling strength and phonon energy of the glass host were calculated and compared to that obtained by Raman spectroscopy. Main intense and longlived luminescence bands are related to the 5D0-7F2 (red) transition of Eu3?, the 5D4-7F5 (green) transition of Tb3? and the 4I13/2-4I15/2 (near-infrared) transition of Er3?. The critical transfer distances, the donor-acceptor interaction parameters and the energy transfer probabilities were calculated using the fitting of the luminescence decay curves from 5D0 (Eu3?), 5D4 (Tb3?) and 4I13/2 (Er3?) excited states. The energy transfer probabilities for Eu3? (5D0), Tb3? (5D4) and Er3? (4I13/2) are relatively small, which indicates low self-quenching luminescence of rare earth ions in lead phosphate glasses.
1 Introduction
Glass materials doped with rare earth ions are widely used
mainly for near-infrared solid-state lasers [14], broadband
optical amplifiers [58], up-conversion systems [911],
optical temperature sensors [12] and optical coherence
tomography [13]. The optically active rare earth ions play a
crucial role in lighting technology and optical display fields
due to emission colors based on their 4f4f
intraconfigurational transitions. Among several amorphous materials
doped with rare earths [1423], oxide and oxyfluoride
phosphates are promising laser hosts because they are able
to accommodate higher content of rare earth ions and still
remain amorphous in comparison with other glass systems.
Their structural and optical properties were characterized
using different spectroscopic techniques in relation to
practical applications such as glass host source emitting
visible light [2430] or near-infrared radiation [3133].
In contrast to lead-free phosphate glass systems,
nearinfrared [3439] and visible [4045] luminescence
investigations of rare earth-doped lead phosphate glasses are less
documented in the literature. Based on thermal and
spectroscopic parameters obtained for rare earth ions, it can be
concluded that lead phosphate glasses present interesting
thermo-optical [3436] and nonlinear optical [37]
properties. Large enhancement of second harmonic generation
(SHG) in cerium-doped lead phosphate glass was also
observed [46]. Generally, the incorporation of PbO to
phosphate glasses increases refractive indices of the host,
which is useful for fabrication of holey fibers. The
observed shift in the absorption edge to higher energies
with increasing PbO content indicates the suitability of
these glasses for optical device applications and makes
them a potential candidate for radiation protection devices
[47].
Here, we present the excitation and luminescence
spectra of selected rare earth ions in lead phosphate
glasses. The optically active rare earth ions were limited to
Eu3?, Tb3? and Er3?. Trivalent europium and terbium ions
in several glass matrices are known as two red and green
primary color light sources, respectively. Our preliminary
investigations indicate that lead-free phosphate glasses [29]
and lead phosphate glasses [45] are promising red-emitting
solid-state materials related to 5D07F2 transition of Eu3?,
whereas quite efficient and long-lived green luminescence
due to 5D47F5 transition of Tb3? ions in phosphate glass
and glass fibers was detected under 483-nm excitation [48].
In contrast to Ln-doped glass systems (Ln = Eu, Tb),
glasses doped with Er3? or codoped with Er3?Yb3? are
studied mainly for near-infrared emission at the third
telecommunication window [49]. The previously published
work by Santos et al [38] indicates that intense broadband
infrared luminescence at 1,530 nm, corresponding to the
main 4I13/24I15/2 laser transition of Er3? ions in lead
phosphate glass, was observed under 800-nm excitation.
Several radiative parameters were calculated based on the
experimental absorption spectrum and the JuddOfelt
theory. An analysis of several parameters such as
luminescence linewidth and lifetime or stimulated emission cross
section suggests that Er3?-doped PbPO4 glass may
potentially be a useful material for developing optical devices.
The investigations into the excitation and luminescence
properties of rare earth ions in glasses are essential to
design optical devices such as solid-state lasers, color
displays, up-converters and optical fiber amplifiers. In this
work, the excitation and luminescence properties of Eu3?,
Tb3? and Er3? ions in lead phosphate glasses are
presented. From excitation spectra of Eu3? ions, the electron
phonon coupling strength and phonon e (...truncated)