MoS
2
saturable absorber for single frequency oscillation
of highly Yb-doped fiber laser
Baole Lu (陆宝乐)
1,2,3,
*, Limei Yuan (原莉梅)
1,2,3
, Xinyuan Qi (齐新元)
4
,LeiHou(侯 磊)
1,2,3
,
Bo Sun (孙 博)
1,2,3
, Pan Fu (付 盼)
1,2,3
, and Jintao Bai (白晋涛)
1,2,3,4
1
National Key Laboratory of Photoelectric Technology and Functional Materials (Culture Base), Institute of Photonics
and Photonics-Technology, Northwest University, Xi’an 710069, China
2
Shaanxi Engineering Technology Research Center for Solid State Lasers and Application, Xi’an 710069, China
3
Institute of Photonics and Photonics-Technology, Provincial Key Laboratory of Photoelectronic Technology,
Northwest University, Xi’an 710069, China
4
School of Physics, Northwest University, Xi’an 710069, China
*Corresponding author: lubaole1123@163.com
Received March 28, 2016; accepted May 16, 2016; posted online June 21, 2016
In this Letter, a single-frequency fiber laser using a molybdenum disulfide (MoS
2
) thin film as a saturable
absorber is demonstrated. We use a short length of highly Yb-doped fiber as the gain medium and a fiber ferrule
with MoS
2
film adhered to it by index matching gel (IMG) that acts as the saturable absorber. The saturable
absorber can be used to discriminate and select the single longitudinal modes. The maximum output power of the
single-frequency fiber laser is 15.3 mW at a pump power of 130 mW and the slope efficiency is 15.3%. The optical
signal-to-noise ratio and the laser linewidths are ∼60 dB and 5.89 kHz, respectively.
OCIS codes: 140.3510, 140.3570, 160.3380.
doi: 10.3788/COL201614.071404.
Single-frequency (SF) lasers have properties of narrow
linewidth, high signal-to-noise ratio (SNR), system com-
pactness, and long operation life. Due to their excellent
characteristics, SF lasers have attracted great attention,
especially the SF fiber lasers around 1 μm, which have very
promising applications in various areas such as cohe rent
telecommunications, optical fiber sensors, laser ranging,
as well as coherent beam combination
[1–4]
.
Different kinds of SF lasers have been realized over the
years. Most previously presented SF solid-state lasers are
based on an intracavity crystal, etalons, and a monolithic
nonplanar ring oscillator
[5–9]
. Although these SF solid-state
lasers have stable structures and high efficiency, the line-
widths are about the MHz level
[7]
. Consequently, several
new methods have been used to realize narrow linewidth
all-fiber lasers in the recent years. Morkel et al. demon-
strated an SF fiber laser with a maximum output power of
over 200 mW and linewidth of less than 7 kHz at 1.95 μmby
using the self-developed heavily Tm
3þ
-doped single-mode
germanate glass fiber as the active fiber in a ring cavity,
and the slope efficiency measured versus the absorbed
pump power was 34.8%
[10]
. Meng et al. reported a 40 Hz
ultra-narrow linewidth SF fiber laser at 1550 nm with a
maximum output power of about 6 mW at 0.37 mW
Brillouin pump power and 383 mW 980 nm pump power
by employing an erbium-doped fiber as both Brillouin
and gain media in a ring cavity
[11]
. The ring cavity fiber laser
exhibits excellent characteristics in the linewidth and in the
output stability. Nevertheless, the complicated structure
and rather low slope efficiency limit the extensive applica-
tions. In addition, the short linear-cavity structures
(distributed Bragg reflector (DBR)
[12]
and distributed
feedback (DFB)
[13]
) are beneficial to SF laser emission for
their narrow linewidth and low noise, which are quite dif-
ficult to fabricate due to their complicated techniques and
expensive costs. For these reasons, a novel type of linear-
cavity fiber laser with a doped fiber in a loop mirror filter
(LMF) as the saturable absorber (SA) is proposed
[14,15]
. The
cavity design is easy to implemen t and costs less.
Recently, the emergence of two-dimensional (2D) mate-
rials has provided another simple way to achieve the SF
laser. Graphe ne, a type of zero bandgap 2D nanomaterial
with a broadband saturable absorption and a low satu-
rable absorbing threshold, is accepted as a prominent
material for the fabrication of high-performance SAs
[16,17]
.
Muhammad et al. employed a multilayer graphene as the
SA in a ring cavity, and then successfully generated a con-
ventional wavelength band fiber laser with a tunable
single-longitudinal-mode laser output
[18]
. Zhou et al. pro-
posed and demonstrated a dual-wavelength SF fiber laser
based on a graphene SA and wave shape. The linewidths
and the side-mode suppression ratios of the two wave-
lengths are both less than 7.3 kHz and larger than 50 dB,
respectively
[19]
. In addition, Chen et al. experimentally
demonstrated a single-longitudinal mode erbium-doped fi-
ber laser with a maximum output power of 23 mW at 1 W
1480 nm pump power and linewidth of less than 10 kHz by
using a topolopical insulator (TI) Bi
2
Te
3
as the SA
[20]
.
Very recently, MoS
2
was a typical transition metal dichal-
cogenide in which hexagonal layers of molybdenum atoms
were sandwiched between two layers of chalcogen atom
(S). MoS
2
has a natural direct bandgap, which is adjust-
able according to the number of layers. Wang et al. re-
ported that the MoS
2
nanosheets have a better saturable
COL 14(7), 071404(2016) CHINESE OPTICS LETTERS July 10, 2016
1671-7694/2016/071404(5) 071404-1 © 2016 Chinese Optics Letters