Optical Materials 125 (2022) 112140
0925-3467/© 2022 Published by Elsevier B.V.
Influence of Bi
+
ions on photoluminescence properties of Tm
2
O
3
doped
borotellurite glasses for the near-infrared emission applications
Abely M. Elias
a
, Stanley Ferdinand Mwanga
a
, Benard Mwankemwa
a
, Anjaiah J
b
,
Laxmikanth C
a, *
a
Energy and Materials Research Lab, Department of Physics, The University of Dodoma, East Africa, Tanzania
b
Department of Physics, Geethanjali College of Engineering and Technology, Keesara, Medchal Dist., Telangana, 501 301, India
A R T I C L E INFO
Keywords:
Borotellurite glasses
UV–Vis–NIR absorption
Photoluminescence
Thulium ions and judd-ofelt parameters
ABSTRACT
This paper reports the influence of bismuth ions (Bi
+
) on photoluminescence properties of Tm
2
O
3
doped bor-
otellurite based glasses (BTGS) with the composition (64-y)B
2
O
3
–30TeO
2
– 5NaF- yBi
2
O
3
–1Tm
2
O
3
, where y = 0,
4, 8, 12 and 16 wt% for the near-infrared (NIR) emission applications. All glasses were prepared using the melt-
quenching method and confirmed to exhibit amorphous nature by the X-ray diffraction (XRD) technique. The
absorption spectra in the wavelength range of 300–2100 nm and emission spectra in the wavelength range of
400–2200 nm were studied. Increase of y wt. % value increases the
3
H
4
→
3
F
4
and
3
F
4
→
3
H
6
(near-infrared, NIR
emission) intensities due to cross-relaxation (CR) and enhanced energy transfer processes between the active
centres (Bi
+
and Tm
3+
ions), which are strongly influenced by bismuth content (Bi
+
) in the glass matrix. Based on
Judd-Ofelt theory, the intensity parameters Ω
2
, Ω
4
and Ω
6
for each glass were determined and found to follow the
trend Ω
2
>Ω
4
>Ω
6
similar to the recently reported photonic glasses. Using the Ω
λ
parameters and reduced matrix
elements, the calculation for the emission transition probability (A), radiative lifetime (τ
R
), branching ratio (β
R
)
and emission-cross sections (σ
E
P
) of
3
H
4
,
3
H
5
, and
3
F
4
energy levels were done and found to be slightly higher than
fluoride and other oxide-based glasses because of the high density and refractive index values of the present
samples.
1. Introduction
Recently, there has been a great effort in the development of quality
optical systems operating in the NIR regions of an electromagnetic
spectrum which is driven by several potential applications such as lasers
for medical surgery, in the military, developing multifunctional 3D
sources as well as atmospheric pollution monitoring [1–4]. Due to the
environmentally friendly nature and provision of broad emission bands
covering neodymium and erbium systems, Tm
2
O
3
doped glasses are
well-known candidates for mid-infrared devices [1,5]. Indeed, Tm
3+
ions possess a
3
H
6
ground state, which is easily pumped by readily
available 802 nm laser diode (LD); thus, the fabrication cost of Tm
3+
ions doped glasses is minimum. Besides, for efficient NIR laser opera-
tion, high Tm
2
O
3
concentration is needed [6]. However, the concen-
tration quenching effect is the main challenge in this area. In view of
this, fluoride-based glasses have been extensively investigated and re-
ported as the best candidates for highly rare-earth doping. Still, these
glass hosts require a more complex fabrication route [7,8]. On the other
hand, compared to fluoride glass systems, borotellurite glass hosts have
improved rare-earth ion compatibility, thermal stability, excellent
transparency in the visible and infrared regions (0.4–6 μm) [9,10].
Good chemical durability, relative low phonon energy (700–750
cm
1
) requirement, and low non-radiative decay of borotellurite glasses
make them luminescence quantum efficient materials [9–13].
Moreover, bismuth contained glasses have been reported to be the
new optical materials for the infrared (IR) performance due to the
exhibition of broad luminescence spectra (1000–1700 nm) and high
radiative lifetimes of the upper transition states (0.1–1 ms) [14,15].
Despite the advanced research on borotellurite based glasses, how-
ever, there is little information on the influence of Bi
+
ions on the
photoluminescence properties of Tm
2
O
3
doped borotellurite glass sys-
tem; thus, in the present work, it is investigated the effect of Bi
+
on the
photoluminescence properties of Tm
2
O
3
doped (1.0 wt%) borotellurite
glass system (BTGS) to explore specifically the influence of Bi
+
ions in
* Corresponding author.
E-mail address: htnakimxal@gmail.com (L. C).
Contents lists available at ScienceDirect
Optical Materials
journal homepage: www.elsevier.com/locate/optmat
https://doi.org/10.1016/j.optmat.2022.112140
Received 14 December 2021; Received in revised form 9 February 2022; Accepted 20 February 2022