Nanosecond-pulsed, dual-wavelength, passively
Q-switched ytterbium-doped bulk laser based on
few-layer MoS
2
saturable absorber
Fei Lou,
1
Ruwei Zhao,
1
Jingliang He,
1,
* Zhitai Jia,
1
Xiancui Su,
1
Zhaowei Wang,
1
Jia Hou,
1
and Baitao Zhang
1,2
1
State Key Laboratory of Crystal Materials, Shandong University, Jinan 250100, China
2
e-mail: bai3697@126.com
*Corresponding author: jlhe@sdu.edu.cn
Received November 14, 2014; revised January 7, 2015; accepted January 21, 2015;
posted January 26, 2015 (Doc. ID 226807); published March 23, 2015
A compact saturable absorber mirror (SAM) based on few-layer molybdenum disulfide (MoS
2
) nanoplatelets was
fabricated and successfully used as an efficient saturable absorber (SA) for the passively Q-switched solid-state
laser at 1 μm wavelength. Pulses as short as 182 ns were obtained from a ytterbium-doped (Yb:LGGG) bulk laser
Q-switched by the MoS
2
SAM, which we believe to be the shortest one ever achieved from the MoS
2
SAs-based
Q-switched bulk lasers. A maximum average output power of 0.6 W was obtained with a slope efficiency of 24%,
corresponding to single pulse energy up to 1.8 μJ. In addition, the simultaneous dual-wavelength Q-switching at
1025.2 and 1028.1 nm has been successfully achieved. The results indicate the promising potential of few-layer
MoS
2
nanoplatelets as nonlinear optical switches for achieving efficient pulsed bulk lasers. © 2015 Chinese Laser
Press
OCIS codes: (140.3580) Lasers, solid-state; (160.4330) Nonlinear optical materials; (160.4236)
Nanomaterials.
http://dx.doi.org/10.1364/PRJ.3.000A25
1. INTRODUCTION
For the generation of nanosecond pulses and subnanosecond
pulses, passive Q-switching (QS) and mode locking by incor-
poration of saturable absorbers (SAs) have been extensively
employed as a consequence of their excellent mechanical sta-
bility and compactness. The SA plays a key role in periodically
modulating the intracavity loss and turning the continuous-
wave (CW) laser into pulse trains. Cr
4
:YAG as a powerful
SA has been widely used in solid-state lasers, while it has
some limitations such as the relatively high cost. The applica-
tion of semiconductor saturable absorber mirrors (SESAMs)
as Q-switchers is limited because of their complicated and ex-
pensive manufacturing technology and narrow operation
waveband. Thanks to the excellent saturable absorption prop-
erties and high thermal stability, low-dimensional carbon
nanostructures have emerged as promising SAs in recent
years [
1–4]. With graphene-based SAs, ultrafast pulse genera-
tion in the wavelength range between 0.8 and 2.5 μm has been
realized [5–11]. As for the graphene-based QS operation, sys-
tematic studies in the spectral region of 0.9 to 2 μm are also
performed with impressive results given out [
12–16]. The suc-
cess of graphene being applied in pulsed lasers motivates the
exploration of other graphene-like two-dimensional (2D) ma-
terials. Recently, a rising Dirac material called topological
insulators (TIs) with an insulating bulk state and gapless
Dirac-type surface/edge has attracted great interest in con-
densed-matter physics, which has been verified with broad-
band saturable absorption properties experimentally [
17–19].
Utilizing the saturable absorption of TI, Tang et al. obtained
pulses with pulse widths of 6.3 μs from an Er:YAG bulk laser
by using a Bi
2
Te
3
SA [20]. Using a Bi
2
Se
3
SA and a Nd:YVO
4
crystal, Q-switched pulse widths as short as 250 ns are
achieved, which are the shortest ones from the TI-based
Q-switched lasers [
21]. In the fiber lasers, TI-based SA devices
also demonstrate promising characteristics for realizing
pulsed lasers [
22–25].
In addition, molybdenum disulfide (MoS
2
) as a typical
transition-metal dichalcogenide is now under continuously
rising attention due to its thickness-dependent electronic
and optical properties. Unlike graphene, which possesses
very weak second-order nonlinearity, few-layer MoS
2
shows an interesting layer-dependent [26,27] or orientation-
dependent second-order nonlinearity [
28], determined by
the unique symmetry of its lattice structure. The MoS
2
disper-
sions have shown stronger saturable absorption responses
than graphene dispersions [
29]. Furthermore, it was interest-
ing to note, by introducing suitable defects in MoS
2
, the
bandgap of MoS
2
atomic layers decrease to 0.26 eV, corre-
sponding to an absorption edge up to about 4.7 μm[
30]. With
broadband few-layer MoS
2
as SAs, passively Q-switched and
ultrafast lasers have been realized [
30–36]. Zhang et al. re-
ported a MoS
2
-based optical fiber SA device that fits the
mode-locking operation of an ytterbium-doped fiber laser
and experimentally generates nanosecond dissipative soliton
pulses at 1054 nm [
32]. At 1.5 μm wavelength region, the ultra-
short pulse generation from an erbium-doped fiber laser
mode-locked by multilayer MoS
2
-based SAs were also demon-
strated [
33,34]. In bulk lasers employing the MoS
2
samples as
SAs, a passively Q-switched Nd:GdVO
4
laser at a wavelength
of 1.06 μm has been realized [
30], from which the minimum
Lou et al. Vol. 3, No. 2 / April 2015 / Photon. Res. A25
2327-9125/15/020A25-05 © 2015 Chinese Laser Press