тысячи (Spectroscopic properties of fluorophosphate glass with high Er3+ concentration)
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Spectroscopic properties
of fluorophosphate glass
with high Er3+ concentration
ABSTRACT Fluorophosphate glass with 4 mol.% ErF3 content
was prepared. The different scanning calorimetry was
conducted. Raman spectrum, infrared transmission spectrum,
absorption spectrum were measured. Fluorescence spectrum
and lifetime of emission around 1.53 μm were measured under
970 nm laser diode excitation. The metaphosphate content in
the composition is limited, but the maximum phonon energy of
glass amounts to 1290 cm−1, and is comparatively high. The
full width at half maximum is about 56 nm, and is wider than
for most of the materials investigated. The measured lifetime of
4I13/2 → 4I15/2 transition, contributed by the high phonon energy,
inefficient interaction of Er3+ ions, and low water content,
amounts to no less than 7.36 ms though the Er3+ concentration
is high. This work might provide useful information for the
development of compact optical devices.
1 Introduction
In recent years researchers have paid a great deal
of attention tominiature rare earth-doped glass devices. Compact
devices such as microchip lasers, amplifiers, lossless
splitters, and waveguide lasers have already been demonstrated
[1–5]. Among them erbium-doped glass waveguides
have been of particular interest because of their potential for
use as active elements in integrated optical devices for optical
communication system.
Miniature devices, which are only a few centimeters in
length, require the glass to provide a gain per unit length
as large as possible. The gain per unit length is linear proportional
to NEr ×τ ×σemi, where NEr is the concentration
of Er3+ ions, τ is the fluorescence lifetime of Er3+: 4I13/2 →
4I15/2 transition and σemi is the stimulated-emission cross section,
so in order to obtain high gain per unit length, the concentration
of Er3+ ions should be as high as possible. However,
the concentration is limited by the concentration quenching.
Generally the concentration of Er3+ ions for the onset of concentration
quenching is no more than 1–2×1020 ions/cm3
for tellurite glasses or phosphate glasses [6, 7]. Above the
concentration, the lifetime decreases sharply with the increase
of Er3+ concentration. The fluorescence lifetime of
Er3+: 4I13/2 → 4I15/2 transition is a critical factor not only
because it contributes to high gain properties, but also because
a long lifetime permits the required high population
inversion to be obtained under steady-state conditions by exertion
of modest pump power [8]. In this paper, a glass with
considerably high Er3+ concentration as well as long fluorescence
lifetime was obtained. The Er3+ concentration is
7.45×1020 ions/cm3, and the measured lifetime amounts to
no less than 7.36 ms.