Passively Q-switched lasers at 1.06
l
m with graphene oxide and carbon
nanotubes D
2
O dispersion
Tianli Feng
a
, Shengzhi Zhao
a
, Kejian Yang
a,
⇑
, Jia Zhao
a
, Guiqiu Li
a
, Dechun Li
a
, Wenchao Qiao
a
, Tao Li
a
,
Xintian Chen
a
, Cheng Liu
a
, Yonggang Wang
b
a
School of Information Science and Engineering, Shandong University, Jinan, China
b
State Key Laboratory of Transient Optics and Photonics, Xi’an Institute of Optics and Precision Mechanics, Chinese Academy of Sciences, Xi’an, China
article info
Article history:
Received 29 November 2013
Received in revised form 7 February 2014
Accepted 7 March 2014
Available online 29 March 2014
Keywords:
Graphene oxide
Single walled carbon nanotubes
D
2
O dispersion
Q-switching
abstract
We have investigated the passive Q-switching characteristics of graphene oxide (GO) and single walled
carbon nanotubes (SWCNTs) D
2
O (heavy water, deuteroxide) based on a diode-pumped YVO
4
/Nd:YVO
4
laser for the first time as far as we know. By using 20 mg/10 ml GO D
2
O dispersion, pulses with minimum
duration of 344 ns under a repetition rate of 550 kHz were obtained. With 0.3 mg/10 ml SWCNTs D
2
O
dispersion, a maximum pulse energy of 1.2
l
J with duration of 530 ns was achieved at a repetition rate
of 178 kHz.
Ó 2014 Elsevier B.V. All rights reserved.
1. Introduction
Solid-state nanosecond lasers at 1
l
m are of great interest due
to their wide applications in micromachining, ranging, remote
sensing, and microsurgery [1–3]. To realize such laser sources, pas-
sive Q-switching method with the aid of saturable absorbers (SAs)
was always preferred due to the advantages of simplicity, reliabil-
ity and compactness. To date, passively Q-switched solid-state
lasers in 1
l
m region with GaAs [4] and Cr
4+
-doped crystals [5]
as SAs have been well developed. At the same time, the efforts to
investigate novel SAs suitable for 1
l
m lasers are still undergoing.
In recent years, 1D and 2D forms of carbon, graphene and CNTs
have attracted much attention for their excellent optical and
physical properties. Unlike the traditional SAs, both graphene
and CNTs possess the virtues of low-cost, easy of fabrication, and
broadband absorption [6,7], as well as the particularly low satura-
tion intensity and ultra-fast relaxation time which makes them
very suitable for fast SAs. As SAs, although graphene owns an ultra-
fast recovery time 200 fs and a low saturable absorption thresh-
old 0.7 MW/cm
2
which are superior to those of CNTs (500 fs
and 5.1 MW/cm
2
) [8,9], the poor water solubility of graphene
have a negative impact on its processing capability. For this reason,
strongly hydrophilic and water soluble GO are developed. Of
course the GO also has a fast recovery time and strong saturable
absorption comparable with graphene [10].
On the other hand, in order to be adapted to different lasers,
several ways have been proposed to deposit graphene/GO or CNTs
on suitable optical components. In solid-state lasers, graphene/GO
and CNTs are usually deposited on substrates such as SiC, quartz
plate or polymer as SAs [11–13]. While for fiber lasers, graphene/
GO and CNTs are usually directly deposited on fiber end [7] or
side-polished fiber [8,9], and sometimes are deposited on a sepa-
rate optical component [14,15]. In either solid state lasers or fiber
lasers, the graphene/GO and CNTs SAs were mostly employed in
solid phase, which required several steps to be fabricated, so a sim-
plified way to use graphene/GO and CNTs as SAs are expected.
However, absorbers in solid-state will suffer from two damages:
(a) physical damage from the contact between the substrate and
the SWCNT and (b) optical power induced thermal damage.
Recently, liquid absorber was demonstrated [16–18]. Ref. [16]
demonstrated a liquid saturable absorber by fabricating a micro-
channel through the core of a conventional fiber and filling it with
SWCNTs dispersed in dimethylformamide (DMF). Ref. [17] showed
a saturable absorber incorporating a hollow optical fiber filled with
SWCNT/polymer dispersed in dichlorobenzene (DCB) solution.
Both the above liquid absorbers were organic solutions, which
had the shortcoming of excessive evaporation speed. Ref. [18] pre-
sented an absorber made of GO aqueous dispersion filled photonic
crystal fiber. However, high absorption loss was produced in water
so that the output power was seriously limited. In our experiment,
http://dx.doi.org/10.1016/j.optmat.2014.03.014
0925-3467/Ó 2014 Elsevier B.V. All rights reserved.
⇑
Corresponding author.
E-mail address: k.j.yang@sdu.edu.cn (K. Yang).
Optical Materials 36 (2014) 1270–1273
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Optical Materials
journal homepage: www.elsevier.com/locate/optmat