Experimental investigation on Q-switching and
Q-switched mode-locking operation in gold
nanorods-based erbium-doped fiber laser
Xude Wang (汪徐德)
1,2
, Nian Zhao (赵 年)
2
,HaoLiu(刘 浩)
2
, Rui Tang (汤 瑞)
2
,
Yanfang Zhu (朱艳芳)
4
, Jianping Xue (薛建平)
4
, Zhichao Luo (罗智超)
2
,
Aiping Luo (罗爱平)
2,3,
*, and Wencheng Xu (徐文成)
2,
**
1
School of Physics and Electronic Information, Huaibei Normal University, Huaibei 235000, China
2
Laboratory of Nanophotonic Functional Materials and Devices, School of Information and Optoelectronic
Science and Engineering, South China Normal University, Guangzhou 510006, China
3
Guangdong Provincial Key Laboratory of Fiber Laser Materials and Applied Techniques,
South China University of Technology, Guangzhou 510640, China
4
School of Life Sciences, Huaibei Normal University, Huaibei 235000, China
*Corresponding author: luoaiping@scnu.edu.cn; **corresponding author: xuwch@scnu.edu.cn
Received March 15, 2015; accepted May 7, 2015; posted online June 11, 2015
We report on the generation of Q-switched and Q-switched mode-locked (QML) pulses in an erbium-doped fiber
ring laser by using a polyvinyl alcohol (PVA) -based gold nanorod (GNR) saturable absorber (SA). The PVA-
based GNR SA has a modulation depth of ∼4.8% and a non-saturable loss of ∼26.9% at 1.5 μm. A Q-switched
pulse train with a repetition rate varying from 18.70 to 39.85 kHz and a QML pulse train with an envelope
repetition rate tuning from 20.31 to 31.50 kHz are obtained. Moreover, the lasing wavelengths of the Q-switched
pulses can be flexibly tuned by introducing a narrow bandwidth, tunable filter into the laser cavity. The results
demonstrate that the GNRs exhibit good optical performance and can find a wide range of applications in the
field of laser technology.
OCIS codes: 140.3500, 140.3540, 140.3600, 160.4236.
doi: 10.3788/COL201513.081401.
Fiber lasers capable of generating Q-switched and
Q-switched mode-locked (QML) pulses have attracted
considerable attention for their widespread applications,
which range from basic research to optical communica-
tion, spectroscopy, and material processing that relies
on their high-pulse energy output and controllable repeti-
tion rate
[1,2]
. At present, both actively and passively mode-
locked techniques have been used to achieve Q-switched
and QML pulses in fiber lasers. Introducing electro- or
acousto-optic modulators enables the actively Q-switched
fiber laser to attain a tunable and robust repetition rate.
However, the cumbersome and complicated laser systems
limit their wide range application
[3]
. On the contrary,
passively Q-switched fiber lasers have the advantages of
compactness and simplicity because they use different
kinds of saturable absorbers (SAs). The metal-doped bulk
crystal and the semiconductor saturable absorber mirror
(SESAM) are the most commo n SAs used for the passive
Q-switching operation
[4,5]
. However, the complex fabrica-
tion process and limited operation bandwidth of SESAMs
should be taken into consideration. Such limitations
motivate research on new materials for SAs. Recently,
novel nanomaterials such as the carbon nanotube
[6–8]
,
graphene
[9–11]
, and the topological insulator
[12–14]
have been
intensively studied due to their fast recovery time, large
third nonlinearity, and broadband saturable absorption
characteristics. They show excellent optical performance
and good compatibility with the fiber laser, and can be
integrated into the cavity to construct a compact,
Q-switched fiber laser
[15–21]
.
Very recently, gold nanorods (GNRs) have gained par-
ticular interest due to the unique features of their surface
plasmon resonances (SPRs), which originate from the col-
lective oscillations of the conduction electrons. There are
two SPR absorption peaks in the absorption spectrum of
GNRs. One is the longitudinal SPR absorption peak, while
the other is the transverse one. Interestingly, the position
of the longitudinal SPR absorption peak can be widely
tuned by varying the aspect ratio of the nanorods, and
then can be conveniently shifted to the near-infrared re-
gion, which is in the operation waveband of fiber lasers. In
addition, the saturabl e absorption of the longitudinal SPR
has been observed with the z-scan technique. The third-
order nonlinear optical properties of GNRs have been
investigated as well
[22,23]
, suggesting that the GNRs could
function as a promising nanomaterial for the fabrication of
high-performance SAs. Indeed, by virtue of the advantage
of large nonlinearity, picosecond recovery time, and tun-
able saturable absorption waveband, GNRs are used in
fiber laser as SAs for realizing passively Q-switched oper-
ations
[24,25]
. To further exploit the potential applications in
a GNR-based fiber laser, it is necessary to investigate
a wavelength-tunable Q-switched operation and a QML
operation.
COL 13(8), 081401(2015) CHINESE OPTICS LETTERS August 10, 2015
1671-7694/2015/081401(5) 081401-1 © 2015 Chinese Optics Letters