Coexistence of bound soliton and harmonic mode-locking
soliton in an ultrafast fiber laser based on MoS
2
-deposited
microfiber photonic device
Meng Liu (刘 萌)
1,2
, Aiping Luo (罗爱平)
1,2
, Wencheng Xu (徐文成)
1,2
,
and Zhichao Luo (罗智超)
1,2,
*
1
Guangdong Provincial Key Laboratory of Nanophotonic Functional Materials and Devices & Guangzhou Key
Laboratory for Special Fiber Photonic Devices and Applications, South China Normal University,
Guangzhou 510006, China
2
Guangdong Provincial Engineering Technol ogy Research Center for Microstructured Functional Fibers and Devices,
South China Normal University, Guangzhou 510006, China
*Corresponding author: zcluo@scnu.edu.cn
Received October 30, 2017; accepted December 22, 2017; posted online Janu ary 26, 2018
As the typical material of two-dimensional transition metal dichalcogenides (TMDs), few-layered MoS
2
pos-
sesses broadband saturable absorption and a large nonlinear refractive index, which could be regarded as a prom-
ising candidate for dual-function photonic device fabrication. In this work, the coexistence of a bound soliton and
harmonic mode-locking soliton was demonstrated in an ultrafast fiber laser based on a MoS
2
-deposited micro-
fiber photonic device. Through a band-pass filter, each multi-soliton state was investigated separately. The
bound soliton has periodic spectral modulation of 1.55 nm with a corresponding pulse separation of 5.16 ps.
The harmonic mode-locking soliton has the repetition rate of 479 MHz, corresponding to the 65th harmonic
of the fundamental repetition rate. The results indicated that there exist more possibilities of different
multi-soliton composites, which would enhance our understanding of multi-soliton dynamics.
OCIS codes: 160.4330, 140.4050, 140.3510, 250.5530.
doi: 10.3788/COL201816.020008.
Two-dimensional (2D) materials have attracted much
attention since the discovery of graphene in 2004. The
2D materials own many unique properties, such as
wideband absorption, ultrafast carrier dynamics, and
2D planar advantage, which make the 2D materials play
important roles in electronic and photonic applications
[1–3]
.
Especially, graphene, the first of 2D materials, has been
demonstrated to be an excellent saturabl e absorber
(SA) in ultrafast fiber lasers because of its broadband
saturable absorption and ultrafast nonlinear optical
response
[4–6]
. However, the unique zero bandgap structure
of graphene also brings intrinsic disadvantages, namely a
degenerated light modulation ability
[7]
, which would limit
its potential applications in the related photonics fields
requiring strong light–matter interaction. Inspired by
the success of graphene, more efforts have been made
to explore new types of 2D materials, such as topological
insulator
[8,9]
, black phosphorus
[10,11]
, MXene
[12]
, and bismu-
thene
[13]
. Recently, 2D semiconducting transition metal
dichalcogenides (TMDs) have received significant atten-
tion because of their semiconducting properties with
tunable bandgaps and abundance in nature
[14–16]
.MoS
2
is a typical TMD, which has layered-dependent electronic
and optical properties
[17,18]
. In 2013, Wang et al. found that
the few-layer MoS
2
exhibits a stronger saturable absorp-
tion response than graphene at a specific waveband
[19]
.
Then, Zhang et al. demonstrated the broadband saturable
absorption of few-l ayer MoS
2
at 400, 800, and 1060 nm
wavebands by using both open-aperture Z scan and
balanced-detector measurement techniques
[20]
. It indicated
that the MoS
2
could be an excellent candidate for broad-
band SA fabrication. So far, the passive mode-locking or
Q-switching has been achieved experimentally at different
wavebands based on the MoS
2
SA
[21–32]
. Apart from the
broadband saturable absorption, Wang et al. experimen-
tally found that the MoS
2
also possesses a large nonlinear
refractive index
[33]
. Then, it is expected that the MoS
2
could act as a promising material for dual-functional
photonic devices with both saturable absorption and high
nonlinear effect.
On the other hand, in addition to optical pulse sources,
the passively mode-locked fiber lasers could also be re-
garded as great test beds for the investigation of soliton
dynamics. As we know, when the nonlinear effects in
the laser cavity are high enough, the single soliton will
break up into multiple solitons, and then evolve into
different types of multi-solitons through the interac-
tions among solitons, dispersive waves, and continuous
waves
[34,35]
. To date, various kinds of multi-soliton dynam-
ics have been obtained in fiber lasers, such as harmonic
mode-locking soliton
[36–38]
, bound soliton
[39,40]
, soliton
rain
[41,42]
, and noise-like soliton
[43,44]
. The investigations of
multi-soliton phenomena would be meaningful to further
understand the physical features of multi-solitons.
Generally, the fiber laser would operate in one of the
multi-soliton states with certain cavity conditions.
COL 16(2), 020008(2018) CHINESE OPTICS LETTERS February 10, 2018
1671-7694/2018/020008(5) 020008-1 © 2018 Chinese Optics Letters