Different temporal patterns of vector soliton bunching induced
by polarization-dependent saturable absorber
Wei-Cheng Chen
a,
⇑
, Guo-Jie Chen
b
, Ding-An Han
a
, Bin Li
b
a
Department of Photoelectric Information and Engineering, Foshan University, Foshan 528000, China
b
Department of Physics, Foshan University, Foshan 528000, China
article info
Article history:
Received 15 October 2013
Revised 2 January 2014
Available online 14 February 2014
Keywords:
Vector soliton
Soliton bunching
Fiber laser
abstract
A fiber laser with either a polarization-independent semiconductor saturable absorption mirror
(PID-SESAM) or a polarization-dependent SESAM (PD-SESAM) as a passive mode-locker is constructed
for obtaining the vector soliton bunching. The temporal patterns of the soliton bunching generated from
the fiber laser with a PD-SESAM are much more abundant than that in fiber laser with a PID-SESAM. Only
the vibrating soliton bunching is generated from the fiber laser with a PID-SESAM. However, there are
another three interesting temporal patterns of the soliton bunching generated from the fiber laser with
a PD-SESAM except for the vibrating soliton bunching. They are variable length soliton bunching, breath-
ing soliton bunching and stable soliton bunching along the slow axis induced by polarization instability.
It is found that the polarization property of the saturable absorber plays a pivotal role for achieving
different temporal patterns of the soliton bunching.
Ó 2014 Elsevier Inc. All rights reserved.
1. Introduction
A mode-locked pulse generated from the fiber laser usually
shows complex profile structures, instead of a single rigorous
hyperbolic pulse shape. The mode-locked pulse with complex
profile structures is called soliton bunching or multiple-pulse
breakup, which has been attracted much attention recently. There
are different types of the soliton bunching observed in the fiber la-
ser, such as bound soliton bunching [1], restless soliton [2], soliton
molecule [3–5], soliton rain [6,7], and multi-wavelength bound
soliton bunching [8]. Different types of the soliton bunching exhi-
bit different temporal behavior patterns. Amrani et al. was the first
to give a classification for different temporal patterns of the single
wavelength soliton bunching. They described five temporal
patterns of the soliton bunching via an analogy with the states of
the matter, such as soliton gas, supersonic soliton gas flow, soliton
liquid, soliton polycrystal and soliton crystal [9,10].
The formation of the soliton bunching owes to soliton energy
quantization effect [11,12]. The soliton energy quantization effect
favors multiple pulsing in the cavity. The coexistence of the
multiple pulses in the cavity will interact together, which leads to
the formation of temporal patterns. There are different types of
the pulsing interaction [13]. The first type is an interaction through
continuous waves (CW). The second one is related to the presence
of the resonant dispersive waves, and the last one is a direct inter-
action between solitons close together. Thus, the configuration of
the soliton bunching is probably either multiple-pulse structure
or the central pulse with concomitant dispersive waves. Some
physical effects are also found to have important effects on the for-
mation of temporal patterns of the soliton bunching, such as the
recovery time of a saturable absorber [14] and the wave-breaking
effect [15,16]. When the multiple-pulse structure of the soliton
bunching is in the bound state, the soliton bunching evolves into
the soliton molecule. According to the definition of soliton phase
states proposed by Amrani et al., the states of soliton liquid, soliton
polycrystal and soliton crystal belong to the soliton molecule.
The above-mentioned different temporal patterns of the soliton
bunching have been achieved in a ring mode-locked fiber laser
with a nonlinear polarization rotation (NPR) technique [9,10] or a
figure-of-eight one with a nonlinear amplifying loop mirror
(NALM) [17]. Some temporal patterns of the soliton bunching have
been observed in other fiber lasers with a real saturable absorber,
such as the SESAM [2], graphene [18–20], topological insulator
[21–24] and carbon nanotube based saturable absorber [25]. Until
now, the temporal patterns of the soliton bunching generated from
a NPR-based fiber laser are achieved more easily than those from
other fiber lasers. In the NPR-based fiber laser, a polarizer is incor-
porated into the ring cavity as an artificial saturable absorber.
Hence, we assume that the polarization property of a saturable
absorber is probably another pivotal role for achieving various
temporal patterns of the vector soliton bunching.
http://dx.doi.org/10.1016/j.yofte.2014.01.010
1068-5200/Ó 2014 Elsevier Inc. All rights reserved.
⇑
Corresponding author.
E-mail address: chenwch@163.com (W.-C. Chen).
Optical Fiber Technology 20 (2014) 199–207
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Optical Fiber Technology
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