COL 10(3), 031402(2012) CHINESE OPTICS LETTERS March 10, 2012
90.4-W all-fiber single-frequency polarization-maintained
1 083-nm MOPA laser employing ring-cavity
single-frequency seed oscillator
Jiangming Xu (许许许将将将明明明), Rongtao Su (粟粟粟荣荣荣涛涛涛), Hu Xiao (肖肖肖 虎虎虎), Pu Zhou (周周周 朴朴朴), and Jing Hou (侯侯侯 静静静)
∗
College of Optoelectronic Science and Engineering, National University of Defense Technology, Changsha 410073, China
∗
Corresp onding author: houjing25@sina.com
Received July 22, 2011; accepted September 15, 2011; posted online November 18, 2011
A high-p ower all-fiber single-frequency polarization-maintained (PM) laser operating at 1 083 nm is demon-
strated using a master oscillator p ower amplifier (MOPA) structure. The seed source of this MOPA laser
system is an in-house-built ring-cavity fiber oscillator. Four-stage amplification configuration is employed,
in which the maximal output power of the main amplifier is 90.4 W, corresponding to a conversion efficiency
of 72.5%. The polarization extinction ratio of the output light is 13 dB. The amplified spontaneous emis-
sion is suppressed by a factor of over 25 dB, and no stimulated Brillouin scattering effect is observed when
a large-mode-area and high absorption coefficient PM gain fib er is employed.
OCIS codes: 060.2320, 140.3560, 140.3615.
doi: 10.3788/COL201210.031402.
High-power fiber lasers are very important components of
materials processing, industrial production, and remote
sensing due to their high beam quality and conversion
efficiency as well as maintenance-free operation
[1−2]
. Es-
pecially, many applications, such as atom trapping and
cooling, nonlinear frequency conversion, coherent beam
combination, and gravitational wave detection, require
polarization-maintained (PM) laser sources
[3−5]
. High-
power single-frequency PM fiber lasers have attracted
increasing research attention in recent years, because the
SBS threshold can be increased to a level that is greater
than 100 W by enlarging the fiber core and the effective
mode field can be scaled up by applying a tempera-
ture gradient along the fiber length; in addition, near-
diffraction-limited beam quality can be obtained with
modern fibers and techniques, such as coiling and mode
matching
[2,5−8]
. Meanwhile, 1 083-nm laser sources with
a narrow linewidth have found widespread applications
in atomic/molecular spectroscopy, such as thermometric
lidar and medical lung diagnostics
[9,10]
.
There are many reports on high-power single-frequency
PM fiber lasers in the last decade. Liem et al. demon-
strated a 100-W-level single-frequency master oscillator
power amplifier (MOPA) laser at 1 064 nm employ-
ing a Nd:YAG nonplanar ring oscillator (NPRO) seed
source
[6]
. Gray et al. reported 264- and 402-W single-
frequency single-mo de plane-polarized MOPA sources
at 1 060 nm, using a distributed-feedback (DFB) seed
laser, respectively
[2,7]
. Qi et al. presented a 128-W class
single-frequency line-polarized fiber amplifier at 1 064
nm with a DFB seed laser
[8]
. Most of these high-p ower
single-frequency PM fiber lasers typically employ bulk
optics configuration that have strict working conditions,
large size, and low coupling efficiency. The use of all-
fiber components can significantly make the laser more
compact and reliable. Liu et al. reported an all-fiber
single-frequency linearly polarized fiber amplifier with a
maximal output power of 43.8 W at 1 064 nm employing
a DFB seed laser
[11]
. With reference to the seed laser,
most of these reports employed commercial DFB seed
sources.
In this letter, we demonstrate a high-power all-fiber
single-frequency PM MOPA laser. The seed source is an
in-house-built ring-cavity single-frequency fiber oscillator
utilizing a piece of saturable absorb er (SA), two polar-
ization controllers (PCs), and a polarization-dependent
isolator (PD-ISO). The central wavelength of the seed
oscillator is 1 083 nm, with a linewidth of 12 MHz. Four-
stage amplification configuration is employed in our
experiment, and the maximum output power of the main
amplifier is 90.4 W, with a polarization extinction ra-
tio (PER) of 13 dB. The corresponding optical-to-optical
conversion efficiency is 72.5%. Although the SBS thresh-
olds in the PM fibers are much lower than those in non-
PM fibers
[12]
, no SBS effect has been observed in using
LMA and high absorption coefficient PM gain fiber. To
the best of our knowledge, this is the highest power all-
fiber single-frequency PM 1083-nm MOPA laser source
ever reported.
In the proposed method, the seed oscillator was
pumped by a fiber-pig-tailed 976-nm single-mode laser
diode (LD) through a 976/1 080-nm wavelength division
multiplexer (WDM). The insertion losses of WDM for the
pump light and signal light were 0.09 and 0.06 dB, respec-
tively. Single-mode single-clad heavily ytterbium (Yb)-
doped fiber with a length of 25 cm was utilized as the
laser gain medium. The gain fiber had a 6-µm/125 µm-
core/cladding diameter, with a core numerical aperture
Fig. 1. Schematic diagram of the ring-cavity single-frequency
seed oscillator.
1671-7694/2012/031402(4) 031402-1
c
° 2012 Chinese Optics Letters
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