High-power diode-side-pumped Nd:YAG solid laser mode-locked
by CVD graphene
Lifei Li
a
, Xinliang Zheng
b,
n
, Xiaoming Chen
a
, Mei Qi
a
, Zhaoyu Ren
a
, Jintao Bai
a,b
,
Zhipei Sun
c
a
National Key Laboratory of Photoelectric Technology and Functional Materials (Culture Base), and Institute of Photonics and Photon-Technology, N orthwest
University, Xi'an 710069, China
b
Department of Physics, Northwest University, Xi' an 710069, China
c
Department of Micro- and Nanosciences, Aalto University, PO Box 13500, FI-00076 Aalto, Finland
article info
Article history:
Received 9 October 2013
Accepted 31 October 2013
Available online 13 November 2013
Keywords:
Graphene
Mode-locking
Diode-side-pumped
Solid laser
abstract
A simple and effective graphene based saturable absorber is successfully fabricated for high power mode-
locking. Utilizing it, graphene-mode-locking operation is achieved in a diode-side-pumped solid laser for
the first time. A maximum average output power up to 2.1 W is produced at 1064 nm center
wavelength with a pulse duration of 13 ps. To the authors’ knowledge, this is the highest operation
power for a graphene-mode-locked laser. The corresponding pulse energy and peak power are 18.4 nJ
and 1.33 kW respectively.
& 2013 Elsevier B.V. All rights reserved.
1. Introduction
Ultrafast solid-state laser sources have widespread applications in
science, military, and industry fields. Normally, there are several
mode-locking techniques (e.g., active mode-locking, passiv e mode-
locking, additive-pulse mode-locking, Kerr-lens mode-locking) to
produce ultrashort pulses in solid lasers. Among them, passive
mode-locking by saturable absorbers (SAs) is particularly important
[1]. It makes the loss of the pulse center smaller than the pulse wings
through inserting a fast SA into the laser reson ance cavity, thereby
shortens the pulse in successive round trips. Traditional ly, semicon-
ductor saturable absorber mirrors (SESAMs), which were invented in
1992, as SAs, have been mostly used for passively mode-locked solid
lasers. How ev er, SESAMs typicall y fabricat ed by complex and costly
molecular beam epitaxy on distributed Bragg reflectors [2].Mean-
while, they have some dr a wbacks like narrow operation bandwidth,
long response time, and their modulation depth are difficult to
modify . Recently, graphene [3] based saturable absorbers (GSAs), a
novel form of SAs [4], are drawing more and more attention due to
their outstanding properties, such as fast saturable absorbability [5],
wideband tunability [6], and simple fabrication with low cost [7].
But to date, the output power in previously published solid lasers,
which are mode-locked by GSAs [5], [8–12], is only at milliw att level
(e.g., the highest is 360 mW [9]), insufficient for some high-intensity
applications. Although Ref. [1 3] has reported the graphene-oxide
based mode-locked laser with the 3 W output power. Howev er, the
output optical path isn't collinear in this result (i.e., the total power of
two output beams with a certain angle is 3 W). Also, the graphene
oxide is insulating with a mixture of sp
2
/sp
3
regions, and with many
defects a nd gap stat es, which is fundamentally different from
graphene. Therefore, graphene o xide may not offer the same wide
operation bandwidth as GSAs. Moreover, those aforementioned
lasers are all founded on diode-end-pumping. As well known,
diode-end-pumping systems are inconvenient to integrate and there
are more serious thermal problems at high power operation com-
pared with the diode-side-pumping counterparts.
Here, we report a 2.1-W high power passively mode-locked
diode-side-pumped solid laser based on a GSA. This laser centered
at 1064 nm with a pulse duration of 13 ps and a pulse repetition
rate of 114 MHz. To the best of our knowledge, it is the first time to
employ a diode-side-pumped gain module for graphene-mode-
locked lasers, which results in six times higher average output
power than ever reported in Ref. [9].
2. Fabrication and characterization of the GSA
W e chose graphene that grew by the atmospheric pressure
chemical vapor deposition (CVD) method to fabricate the GSA
[1 4,15]. This is because the CVD graphene has lower defects with
larger uniform area in comparison with other growth methods like
Contents lists available at ScienceDirect
journal homepage: www.elsevier.com/locate/optcom
Optics Communications
0030-4018/$ - see front matter & 2013 Elsevier B.V. All rights reserved.
http://dx.doi.org/10.1016/j.optcom.2013.10.093
n
Correspondence to: #229 North Taibai Road, Department of Physics, Northwest
University, Xi’an, China 710069. Tel./fax: þ 86 29 8830 3336.
E-mail address: zhengxl@nwu.edu.cn (X. Zheng).
Optics Communications 315 (2014) 204–207