High Power Laser Science and Engineering, (2018), Vol. 6, e46, 6 pages.
© The Author(s) 2018. This is an Open Access article, distributed under the terms of the Creative Commons Attribution licence (http://creativecommons.org/
licenses/by/4.0/), which permits unrestricted re-use, distribution, and reproduction in any medium, provided the original work is properly cited.
doi:10.1017/hpl.2018.43
In-band pumping avenue based high power
superfluorescent fiber source with record power
and near-diffraction-limited beam quality
Jiangming Xu
1,2
, Jun Ye
1
, Hu Xiao
1,2
, Jinyong Leng
1,2
, Wei Liu
1
, and Pu Zhou
1,2
1
College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, China
2
Hunan Provincial Collaborative Innovation Center of High Power Fiber Laser, Changsha 410073, China
(Received 26 April 2018; revised 9 July 2018; accepted 16 July 2018)
Abstract
High power superfluorescent fiber sources (SFSs), which could find wide applications in many fields such as middle
infrared laser generation, Raman fiber laser pumping and spectral beam combination, have experienced a flourishing
time in recent years for its unique properties, such as short coherence length and high temporal stability. The challenge
for performance scalability of powerful SFS mainly lies on the physical issues including parasitic laser oscillation and
modal instability (MI). In this contribution, by employing in-band pumping avenue and high-order transverse-mode
management, we explore a high power SFS with record power, near-diffraction-limited beam quality and spectral
manipulation flexibility. An ultimate output power of 3.14 kW can be obtained with high temporal stability and a
beam quality of M
2
= 1.59 for the amplified light. Furthermore, the dynamics of spectral evolutions, including red-
shifting of central wavelength and unsymmetrical broadening in spectral wings, of the main amplifier with different seed
linewidths are investigated contrastively. Benefiting from the unique high pump brightness and high MI threshold of
in-band pumping scheme, the demonstrated system also manifests promising performance scaling potential.
Keywords: fiber amplifier; high power; in-band pumping; superfluorescent fiber source
1. Introduction
Thanks to the superior features on short coherence length,
high temporal and thermal stability, broad spectral coverage
and good beam quality, superfluorescent fiber sources
(SFSs) have drawn great attention in the past decades
[1–4]
,
and researches, including spectral evolution
[5]
, operat-
ing wavelength expansion
[6, 7]
, and potential application
exploration
[8, 9]
have been widely investigated. Especially,
the utilizations of high power SFSs in many fields, such
as mid-infrared laser and supercontinuum generation
[10, 11]
,
random fiber laser, and Raman fiber laser pumping
[12–14]
and spectral beam combination
[15]
, have been demonstrated
in recent years for its inherent unique incoherence and
high temporal stability characteristics. Consequently, the
performance scalability of high power SFS is extremely
significant.
As early as 2006, Wang et al. demonstrated the first
hundred-watt-level SFS in a single-stage structure operating
Correspondence to: P. Zhou, College of Optoelectronic Science and
Engineering, National University of Defense Technology, No. 109 Deya
Road, Changsha 410073, China. Email: zhoupu203@163.com
in the 1 µm region by employing multi-mode-offset-core
fiber to suppress the parasitic lasing
[16]
. The highest
powers ever reported from single-stage structured SFSs are
186.3 W
[17]
, 16 W
[18]
and 46 W
[19]
for 1 µm, 1.5 µm, and
2 µm range, respectively. Although previous investigations
have announced that hundred-watt-level high power SFS
can be achieved in a single-stage structure with careful
system parameters design, the further power enhancement
is still a challenge because of the physical parasitic lasing
issue. What is more, the presented high power SFSs in
single-stage structure were often broadband and randomly-
polarized
[16–19]
, while narrowband and polarization char-
acteristics are required in practical applications
[20, 21]
.
Fortunately, employing master-oscillator-power-amplifier
(MOPA) configuration can introduce a new horizon of high
power SFS and leverage the high power SFS with special
spectrum/polarization characteristics
[22–25]
and kilowatts
operating power
[26–30]
. Besides, the output light of MOPA-
structured SFS, in contrast to that of fiber MOPA seeded by
standard resonant-cavity-based oscillator with self-pulsing
effect, also has the advantages of high temporal stability
[2, 4]
.
Despite a maximal power of 2.53 kW achieved from
1
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