Active/passive Q-switching operation of 2 μm Tm,
Ho:YAP laser with an acousto-optical
Q-switch/MoS
2
saturable absorber mirror
LINJUN LI,
1,3,
*XINING YANG,
1,4
LONG ZHOU,
1,4
WENQIANG XIE,
1
YUNLONG WANG,
1
YINGJIE SHEN,
2,8
YUQIANG YANG,
5
WENLONG YANG,
5
WEI WANG,
4
ZHIWEI LV,
3,9
XIAOMING DUAN,
6
AND MINGHUA CHEN
7
1
Heilongjiang Provincial Key Laboratory of Optoelectronics and Laser Technology, Heilongjiang Institute of Technology, Harbin 150050, China
2
School of Opto-Electronic Information Science and Technology, Yantai University, Yantai 264005, China
3
School of Electronic and Information Engineering, Hebei University of Technology, Tianjin 300401, China
4
The Higher Educational Key Laboratory for Measuring & Control Technology and Instrumentations of Heilongjiang Province,
Harbin University of Science and Technology, Harbin 150080, China
5
College of Sciences, Harbin University of Science and Technology, Harbin 150080, China
6
National Key Laboratory of Tunable Laser Technology, Harbin Institute of Technology, Harbin 150001, China
7
Key Laboratory of Engineering Dielectric and Applications, Ministry of Education, Harbin University of Science and Technology,
Harbin 150080, China
8
e-mail: Yingjieyj@163.com
9
e-mail: ZhiweiLV@hebut.edu.cn
*Corresponding author: LLJ7897@126.com
Received 26 February 2018; revised 6 April 2018; accepted 6 April 2018; posted 6 April 2018 (Doc. ID 324784); published 23 May 2018
The active/passive Q-switching operation of a 2 μm a-cut Tm,Ho:YAP laser was experimentally demonstrated
with an acousto-optical Q–switch∕MoS
2
saturable absorber mirror. The active Q-switch laser was operated for
the first time, to the best of our knowledge, with an average output power of 12.3 W and a maximum pulse energy
of 10.3 mJ. The passive Q-switch laser was also the first acquired with an average output power of 3.3 W and per
pulse energy of 23.31 μJ, and the beam quality factors of M
2
x
1.06 and M
2
y
1.06 were measured at the average
output power of 2 W.
© 2018 Chinese Laser Press
OCIS codes: (140.3540) Lasers, Q-switched; (140.3580) Lasers, solid-state.
https://doi.org/10.1364/PRJ.6.000614
1. INTRODUCTION
Solid-state lasers with ultra-sho rt pulses operating in the 2 μm
wavelength range have been attractive due to their high peak
power and pulse energy. Also, they have strong absorption
in water and human tissues, and they are in the eye-safe
band. So, 2 μm solid-state lasers with ultra-short pulses will
be especially promising for applications in medical diag-
nostics, material processing, surgery, ranging, and nonlinear
optical frequency conversion [1–7]. Q-switching techniques
are effective methods to achieve ultra-short pulses (nanosec-
ond or microsecond). Among Q-switching techniques, active
Q-switching with an acousto-optical (AO) Q-switch is an
easy and convenient way to achieve nanosecond (ns) pulse
Q-switching operation of a solid-state laser, which can easily
get a stable pulse train and tunable pulse repetition frequency
as required. The energy of per pulse of the active Q-switched
laser can reach millijoule or even joule level. Laser radiation
has been demonstrated in the 2-μm waveband, for instance,
using a Tm,Ho:YLF crystal, a Tm,Ho:GdVO
4
crystal, a
Ho:YAG crystal, a Ho:YAP crystal, and a Ho:YLF crystal
[8–12].
Different from active Q-switching with extra motivation,
passive Q-switching (PQS) with a saturable absorber (SA) is
a low-cost and compact way to achieve microsecond (μs) pulse
Q-switching operation in the mid-infrared waveband. Due
to the limit of the SA’s damage threshold, the energy per
pulse of the PQS laser achieves only nano or micro joule
level, which is lower than the active Q-switching. Many SAs,
such as semiconductor saturable absorber mirrors (SESAMs),
carbon nanotubes, graphene, black phosphorus, and topologi-
cal insulators with broadband saturable absorption at 1–3 μm,
have been chosen for PQS operations [13–23]. The high dam-
age threshold, ultrafast recovery time, moderate saturation in-
tensity, and broadband saturable absorption from SA have been
used as benchmarks against which to judge an excellent SA
[24,25]. The SESAMs, as saturated absorbers, were used earlier
in the 2-μm waveband, and they have been confirmed in
Tm,Ho:YAG, and Tm:LuAG lasers etc. [26 –29]. However,
614
Vol. 6, No. 6 / June 2018 / Photonics Research
Research Article
2327-9125/18/060614-06 Journal © 2018 Chinese Laser Press