Mid-infrared Q-switch performance of ZrC
YANGYANG LIANG,
1
TAO LI,
1,2,3,
*WENCHAO QIAO,
2
TIANLI FENG,
2,6
SHENGZHI ZHAO,
2
YUEFENG ZHAO,
3,4
YUZHI SONG,
3,4
AND CHRISTIAN KRÄNKEL
5
1
China Key Laboratory of Laser & Infrared System (Shandong University), Ministry of Education, Qingdao 266237, China
2
School of Information Science and Engineering, and Shandong Provincial Key Laboratory of Laser Technology and Application,
Shandong University, Qingdao 266237, China
3
Collaborative Innovation Center of Light Manipulations and Applications, Shandong Normal University, Jinan 250358, China
4
School of Physics and Electronics, Shandong Normal University, Jinan 250358, China
5
Leibniz-Institut für Kristallzüchtung, 12489 Berlin, Germany
6
e-mail: tlfeng@sdu.edu.cn
*Corresponding author: litao@sdu.edu.cn
Received 26 June 2020; revised 21 August 2020; accepted 21 August 2020; posted 29 September 2020 (Doc. ID 401168);
published 19 November 2020
Zirconium carbide (ZrC) wit h layered structure and nanoparticle morphology was prepared by sonication in an
ethyl alcohol solvent. The morphology and saturable absorption properties of the ZrC were systematically analyzed.
By using ZrC nanoparticle coated substrates as saturable absorbers, stable Q-switched 3 μm Er:Lu
2
O
3
lasers were
realized. Pulse durations of 50 ns with pulse energies of 20 μJ and peak power of 0.4 kW are the shortest obtained
with novel-material-based Q-switched lasers in the 3 μm wavelength range.
© 2020 Chinese Laser Press
https://doi.org/10.1364/PRJ.401168
1. INTRODUCTION
Benefiting from the spectral absorption of water peaking at
2.94 μm with an absorption length of only 1 μm, mid-infrared
(IR) lasers around 3 μm are highly demanded for applications
in laser surgery, ophthalmology, and chemical sensing [1].
Laser emission in this range can be generated by optical
parametric oscillators (OPOs) [1–3], antimonide-based heter-
ojunction laser diodes [1,4,5], Raman-shifted lasers [6], tran-
sition-metal-doped II-VI chalcogenide lasers (Cr
2
, Fe
2
)
[7,8], and also by rare-earth-doped lasers (Er
3
[9–11],
Ho
3
[12], and Dy
3
[13]). Among these, Er
3
-based
solid-state lasers are widely used cost efficient lasers in the range
of 2.58–2.94 μm with the advantages of compactness, high ef-
ficiency, good stability, and long operation lifetime. In particu-
lar, a slope efficiency as high as 41% was obtained from a 3 at.%
Er:SrF
2
bulk laser. This is much higher than the theoretical
limit given by the Stokes efficiency of 35% and enabled by
an upconversion process recycling excitation from the lower la-
ser level [14]. The cubic sesquioxides (Y
2
O
3
, Lu
2
O
3
, and
Sc
2
O
3
) providing much better thermo-mechanical properties
than, e.g., SrF
2
and low phonon energies for oxide materials,
are suitable host materials for 3 μm lasers [15]. For example, a
continuous wave (CW) Er∶Lu
2
O
3
laser delivered the highest
output power of 5.9 W of any Er
3
-doped laser operated at
room temperature [9]. Also, ceramic Er∶Lu
2
O
3
is very prom-
ising and up to now delivered an output power of 2.6 W under
11.2 W of pump power in CW operation [11]. Further
improvement of the average output power is feasible by oper-
ating the laser at liquid nitrogen temperatures. Under these
conditions, the thermal conductivity of sesquioxides increases
by nearly an order of magnitude, which enabled a record output
power of 14 W at 2.7 μm in a 2 at.% Er:Y
2
O
3
ceramic laser
under a high pump power of 56 W. In this case, the slope ef-
ficiency amounted to ∼26% [16].
In the past decade, numerous two-dimensional (2D) mate-
rials were widely explored and extensively investigated as novel
types of passive optical modulators. These studies revealed the
outstanding ability of 2D materials in generating 3 μm IR laser
pulses [17,18]. The 244 ns pulses were realized in a graphene
Q-switched ceramic Er∶Lu
2
O
3
laser [11]; a MoS
2
Q-switched
Er∶Lu
2
O
3
laser enabled 335 ns pulses [16], and pulses as short
as 194 ns were obtained from a black phosphorus Q-switched
Ho, Pr :LuLiF
4
(Ho,Pr:LLF) laser [19]. Even though a TiSe
2
Q-switched Ho,Pr:LLF laser yielded an even shorter pulse du-
ration of 160.5 ns [18], the reported results were still inferior to
those achieved with conventional bulk modulators. For exam-
ple, Q-switched with Fe
2
:ZnSe,anEr:Y
3
Al
5
O
12
(Er:YAG)
laser emitted 50 ns laser pulses [20]. By using active Q-switch-
ing based on an electro-optic modulator, the laser can emit even
shorter pulses of 25.2 ns [ 21].
Besides some layered materials, fewer studied bulk materials
have turned out to be suitable modulator materials for
Q-switching and even mode-locking of lasers [22]. Recently,
a bulk-structured WTe
2
-based saturable absorber (SA) consist-
ing of hundreds of monolayers cohered by van der Waals forces
enabled stable mode-locking of an Er-doped fiber at 1556 nm
Research Article
Vol. 8, No. 12 / December 2020 / Photonics Research 1857
2327-9125/20/121857-05 Journal © 2020 Chinese Laser Press
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