Noise-like pulse with a 690 fs pedestal generated from a
nonlinear Yb-doped fiber amplification system
Zexin Zhang (张泽新)
1
, Jinrong Tian (田金荣)
1,
*, Changxing Xu (许昌兴)
1
,
Runqin Xu (徐润亲)
2
, Youshuo Cui (崔友硕)
1
, Bihui Zhuang (庄碧辉)
1
,
and Yanrong Song (宋晏蓉)
1
1
College of Physics and Optoelectronics, Faculty of Science, Beijing University of Technology, Beijing 100124, China
2
Institute of Automation, Chinese Academy of Sciences, Beijing 100190, China
*Corresponding author: jrtian@bjut.edu.cn
Received July 16, 2020; accepted September 11, 2020; posted online October 23, 2020
Noise-like pulses having a pedestal of 690 fs and a spike of 59.6 fs were generated in a nonlinear Yb-doped fiber
amplification system. The seed source is a mode-locked Yb-doped fiber laser by nonlinear polarization rotation,
and dissipative soliton pulses were obtained in it. Then, the dissipative soliton pulses passed through a 7.6 m
dispersive fiber to enhance the dispersion and nonlinearity. Further on, the dissipative soliton pulses were
launched into a Yb-doped fiber nonlinear amplifier, and stable noise-like pulses with a pedestal of 6.26 ps
and a spike of 227 fs were achieved. Finally, by a grating pair, the pedestal and spike of the noise-like pulses
were effectively compressed to 690 fs and 59.6 fs, respectively. To the best of our knowledge, this is the shortest
pedestal demonstrated in noise-like pulses operating at 1 μm.
Keywords: fiber laser; amplifier; compression; noise-like pulse.
doi: 10.3788/COL202018.121403.
Ultrafast fiber lasers have attracted much attention due to
potential applications in optical communication, remote
sensing, micro-machining, medical treatment
[1–3]
, etc. The
pulses generated in ultrafast fiber lasers have desirable
characteristics such as ultra-short duration, high peak
power, and broadband spectrum, which entails the imple-
mentation of mode-locking techniques for the generation
of picosecond or femtosecond pulses. Over the past few
decades, researchers have explored different types of
mode-locking techniques such as solitons, similaritons,
and dissipative solitons (DSs). However, pulse energy scal-
ing for these kinds of pulses is usually limited by nonlinear
effects or damage threshold. Thus, the noise-like pulse
(NLP), reported first, to the best of our knowledge, in
1997
[4]
, has been receiving an increasing amount of atten-
tion due to its great potential in higher energy pulse
generation.
In the past few years, extensive investigations on NLPs
have been presented. Typically, an NLP is composed of
wave-packets with a fine inner structure of sub-pulses
that have stochastically varying durations and peak
intensities
[5]
because of fiber birefringence
[4]
, nonlinear
instability
[6]
, soliton collapsing
[7]
, or the peak power clamp-
ing effect
[8]
. This temporal feature gives rise to a double-
scaled autocorrelation trace with a spike riding upon a
wide and smooth pedestal, which implies a low temporal
coherence. Therefore, NLPs may find various applications
in optical metrology, optical sensing
[9,10]
, optical coherence
tomography, optical communication
[11,12]
, and industrial
micro-machining
[13,14]
, with a favorable combination of
low temporal coherence and high pulse energy. A number
of measures can be implemented to obtain NLPs in fiber
lasers, such as mode locking by nonlinear polarization
rotation (NPR)
[15–19]
, nonlinear optical loop mirror
[20–22]
,
nonlinear amplifying loop mirror
[23,24]
, semiconductor satu-
rable abso rption mirror
[25]
, or other saturable absorber ma-
terials
[26–28]
. Since the first, to the best of our knowledge,
demonstration in 1997
[4]
, the NLP’s pulse duration has
been of great interest because of the difficulty in its com-
pression. The shortest pulse duration of the pedestal and
spike are 920 fs
[29]
and 14.3 fs
[24]
, respectively, in the wave-
length region around 1 μm.
In this Letter, we demonstrated generation and com-
pression of NLPs in a nonlinear Yb-doped fiber amplifica-
tion system in experime nt. The DS pulse from an NPR
mode-locked fiber laser passed a 7.6 m dispe rsive fiber
to enhance the dispersion and nonlinearity. After ampli-
fication in a nonlinear Yb-doped fiber amplifier, stable
NLPs with a pedestal of 6.26 ps and a spike of 227 fs were
achieved. The NLPs were further compressed by a grating
pair, and the pedestal and spike were compressed to 690 fs
and 59.6 fs, respectively. To the best of our knowledge,
this is the shortest pedestal of the NLPs operating at 1 μm.
The experimental setup is depicted in Fig.
1, which is
composed of an oscillator, an amplifier, and a compressor.
Figure
1(a) shows the oscillator, which is an NPR mode-
locked all-normal-dispersion Yb-doped fiber laser pumped
by a laser diode with output power up to 600 mW. In the
fiber laser, two collimators (C1 and C2) are separated by
20 cm. The 3 dB bandwidth of the birefringence filter (BF)
is 12 nm, and a 70:30 output coupler (OC) at 1 μm is used
to couple laser out. The optical isolator (ISO) forces uni-
directional operation. Figure
1(b) illustrates the nonlinear
Yb-doped fiber amplifier. Different from our previous
work
[29]
, a 7.6 m single mode fiber (SMF28) is inserted be-
tween the ISO and the combiner as the dispersive fiber to
COL 18(12), 121403(2020) CHINESE OPTICS LETTERS December 2020
1671-7694/2020/121403(5) 121403-1 © 2020 Chinese Optics Letters