Contents lists available at ScienceDirect
Journal of Luminescence
journal homepage: www.elsevier.com/locate/jlumin
Temperature characteristics of green upconversion fluorescence of Er
3+
-
doped SrGdGa
3
O
7
crystal
Hong-Xue Sun
a,b,1
, Ning Yuan
a,b,1
, Zi-Bo Zhang
c
, Qi Sun
a,b
, Yan Wang
d
, Wing-Han Wong
a,b,e
,
Chao-Yang Tu
d
, Dao-Yin Yu
a,b
, Edwin Yue-Bun Pun
e
, De-Long Zhang
a,b,e,
⁎
a
Department of Opto-electronics and Information Engineering, School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin 300072,
People's Republic of China
b
Key Laboratory of Optoelectronic Information Technology (Ministry of Education), Tianjin University, Tianjin 300072, People's Republic of China
c
Faculty of Engineering, University of Toulouse 3, F-31062 Toulouse, France
d
Fujian Institute of Research on the Structure of Matter, Chinese Academy of Sciences, Fuzhou Fujian Province 350002, People's Republic of China
e
Department of Electronic Engineering and State Key Laboratory of Millimeter Waves, City University of Hong Kong, 83 Tat Chee Avenue, Kowloon, Hong Kong, People's
Republic of China
ARTICLE INFO
Keywords:
Er:SrGdGa
3
O
7
single crystal
Green upconversion
Fluorescence intensity ratio (FIR)
Temperature characteristics
Optical temperature sensing
ABSTRACT
Temperature characteristics of 980-nm-upconverted green 530 and 550 nm fluorescence of Er
3+
-doped
SrGdGa
3
O
7
single crystal have been studied for temperature sensing purposes. To achieve that, a simple ex-
perimental setup has been developed that consists of a 980 nm laser diode, two interference filters, two Si-
photocells and two multimeters, while without use of monochromator or focusing lens for fluorescence col-
lection. The study shows that the Er
3+
-doped SrGdGa
3
O
7
crystal displays strong green emission intensity (hence
good signal-to-noise ratio) and high temperature sensitivity of fluorescence intensity ratio of the 530 and 550 nm
emissions, which is (5.6–104.0) × 10
−3
K
−1
in the considered temperature range 100–430 K, depending on the
temperature. In addition, the experiments were repeated using a spectrometer and consistent results of tem-
perature characteristics were obtained. Present study shows that the Er
3+
-doped SrGdGa
3
O
7
crystal is a pro-
mising host material for optical temperature sensing.
1. Introduction
Recently, there has been growing interest in optical temperature
sensing based on fluorescence intensity ratio (FIR) of rare-earth-doped
materials [1–14], primarily due to their high electrical passiveness,
negligible electromagnetic interference, wide dynamic range and mul-
tiplexing capabilities. Such sensor is promising for indirect temperature
measurement in some peculiar systems where other methods are invalid
or unpractical, such as electromagnetically and/or thermally harsh
environments, some industrial processes which work under non-stan-
dard conditions and demand the development of temperature sensor
capable of controlling and monitoring these processes at the non-stan-
dard condition. In addition, using nano-sized phosphor grains as nano-
thermometer has great application potential in microelectronic circuits,
biological tissues and cells, and is currently a hot topic in nano-tech-
nology.
The advantage of the FIR technique is that it reduces the influence
of different factors such as measuring conditions, resolution and time
exposure. The technique is based on the comparison of the fluorescence
intensities of two temperature-dependent emissions from two closely
spaced energy levels to a lower state of rare-earth ion such as Er
3+
,
Pr
3+
,Yb
3+
,Nd
3+
,Eu
3+
,Dy
3+
,Sm
3+
,Ho
3+
,Tm
3+
[15–18]. Among
these ions, the Er
3+
is particularly suitable for this application. This is
because its
4
S
3/2
and
2
H
11/2
levels are closely spaced (with a small
energy gap ~ 800 cm
−1
) and are hence easily thermalized, resulting in
the temperature-sensitive emission intensity of the
4
S
3/2
→
4
I
15/2
(550 nm) and
2
H
11/2
→
4
I
15/2
(530 nm) transitions. Moreover, the two
transitions have relatively high radiative efficiencies and fluorescent
intensities, and may be obtained easily by using a commercial UV-blue
or near-infrared LD or LED, such as 380 nm LED or 980 nm LD, as an
excitation source (the excitation at the 980 nm wavelength is desired
for biological applications as the auto-fluorescence in biological tissues
is absent there).
Over the past years, a number of papers related to the FIR
http://dx.doi.org/10.1016/j.jlumin.2017.06.063
Received 16 April 2017; Received in revised form 21 June 2017; Accepted 28 June 2017
⁎
Corresponding author at: Department of Opto-electronics and Information Engineering, School of Precision Instruments and Opto-electronics Engineering, Tianjin University, Tianjin
300072, People's Republic of China.
1
Equally contributed authors.
E-mail address: dlzhang@tju.edu.cn (D.-L. Zhang).
Journal of Luminescence 192 (2017) 231–236
Available online 29 June 2017
0022-2313/ © 2017 Elsevier B.V. All rights reserved.
MARK