- Email: [email protected]
Monolayer graphene-based passively Q-switched Nd:YAG laser
Accepted Manuscript Title: Monolayer graphene-based passively Q-switched Nd:YAG laser Author: Hong-Yi Lin Xiao Liu Xiao-Hua Huang Ying-Chao Xu Xian-Guo Meng Fei-Bing Xiong PII: DOI: Reference:
S0030-4026(15)01341-8 http://dx.doi.org/doi:10.1016/j.ijleo.2015.09.249 IJLEO 56454
To appear in: Received date: Accepted date:
4-12-2014 30-9-2015
Please cite this article as: H.-Y. Lin, X. Liu, X.-H. Huang, Y.-C. Xu, X.G. Meng, F.-B. Xiong, Monolayer graphene-based passively Q-switched Nd:YAG laser, Optik - International Journal for Light and Electron Optics (2015), http://dx.doi.org/10.1016/j.ijleo.2015.09.249 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
*Manuscript
Monolayer graphene-based passively Q-switched Nd:YAG laser Hong-Yi Lin a
a, b
c
, Xiao Liu , Xiao-Hua Huang
a, b
, Ying-Chao Xu
a, b
, Xian-Guo Meng
a, b
, Fei-Bing Xiong
a, b
School of Optoelectronic and Communication Engineering, Xiamen University of Technology, Xiamen 361024, China. b
Key Laboratory of Optoelectronic Technology, Fujian Province University, Xiamen 361024, China. c
School of Cultural Industries, Xiamen University of Technology, Xiamen 361024, China.
ip t
Abstract: We demonstrate a pulsed Nd:YAG laser Q-switched by a monolayer graphene. The monolayer graphene is fabricated by the chemical vapor deposition (CVD) method, and then transferred onto the facet
cr
of SiO2 to construct a saturable absorber (SA). The Q-switched largest output power of 266 mW, the maximum repetition rate of 436 kHz, and the narrowest pulse duration of 753 ns have been obtained when
us
the pump power is 3 W.
an
Key words: monolayer grapheme; passively Q-switched; Nd:YAG Laser; CVD.
1 Introduction
M
The Q-switched technique is a fundamental technique to generate high energy pulsed lasers, which are important for applications in the fields of laser processing, medicine, environmental sensing, telecommunications, range finding, material processing, and reflectometry [1, 2]. Unlike the mode-locked
ed
technique, the Q-switched technique has a relatively longer pulse duration and lower repetition rate (usually in the kHz range). Furthermore, Q-switching is able to produce higher pulse energies, higher operation
ce pt
efficiency, and more cost effective than mode-locking [3]. Q-switching can be obtained via one of two approaches, passive method or active method. The passively Q-switched method features a very simpler design and a more compact geometry compared to the active method. A
semiconductor saturable absorber mirror (SESAM) and Carbon nanotubes (CNTs) have been
Ac
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
successfully demonstrated to passively Q-switched lasers. However, the fabrication and packing of SESAMs requires very complex and costly processes. Moreover, the SESAM has a narrow wavelength working range for a laser. CNTs are a comparatively simple and cost effective alternative. Unfortunately, its operation wavelength is related to the diameter and chirality [4, 5]. Compared to SESAM and CNTs, graphene has its perfect optical characteristics, such as low cost, easy of fabrication, ultrafast recovery time, and a higher damage threshold, so it has been widely used to replace SESAM and CNTs [3-6].
2 Characteristics of Monolayer Graphene-based Saturable Absorber Graphene is a Dirac two-dimensional crystal of carbon atoms which arranges in a honeycomb lattice.
Page 1 of 7
Isolated grapheme nanosheets were firstly produced in 2004 by K. S. Novoselov, who wined the 2010 Nobel Prize of physics [7]. Graphene has very excellent linear and nonlinear optical properties, such as low nonsaturable loss, ultrafast recovery time (200 fs), and an ultrabroad wavelength independent saturable absorption range, which covers the laser wavelength range from the visible, infrared to terahertz wavelength region and shows little wavelength dependence [8]. The cause for saturable absorption of graphene is due to Pauli blocking. The conduction band and
ip t
valence band of graphene intersect at the Dirac point. Because graphene has a zero bandgap, it can absorb all photons ranging from the visible to terahertz wavelength region and show little wavelength dependence
cr
[9]. The photonic characteristics of graphene are significant shown in Fig. 1. If low intensity light incident,
us
photons are highly absorbed, and the electrons in the valence band will be excited up to conduction band of the graphene SA material. However, if high intensity light incident, according to the Pauli blocking principle, the conduction band will be filled easily and some photons are not absorbed. Therefore, only high intensity
ed
M
an
light can pass through the SA with very low loss and vice versa.
1064 nm
ce pt
4I 11/2
Fig.1. The characteristics of graphene SA material.
The Raman spectrum of the CVD monolayer grapheme is shown in Fig. 2, and it exhibits the prominent
Ac
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
peaks at Raman shift of approximately 1329, 1564, and 2681 cm-1, generally known as D, G, and 2D band, respectively. D band is associated with vibrations of carbon atoms with sp3 electronic configuration of disordered graphite. G-band contributes to an E2g mode of graphite and is related to the in-plane vibration of sp2-bonded carbon atoms. The intensity ratio of the D and G bands is about 0.22, indicating few defects and good quality in graphene sample [8-10]. Intensity ratio between G and 2D peak can be used to reduce the number of layer. Single-layer grapheme has a low intensity ratio, usually lower than or close to 0.5; while multilayer graphene shows higher intensity ratio, usually larger than 1 [10]. As shown in Fig. 2, the G/2D peak ratio of 0.53 indicates that we obtain monolayer graphene. Besides that, another way to distinguish the monolayer from multilayer one is full-width half maximum (FWHM) of the 2D peak [11]. The FWHM of 2D Page 2 of 7
peak is smaller as the number of graphene layers decrease. As shown in Fig. 2, the FWHM of 2D peak is only 33 cm-1, it can be suggest that the graphene sample is monolayer [8]. 1800
2D
1600
1200
G
1000 800
ip t
Intensity , a. u.
1400
600 400
D 0 1000
1500
2000
2500
-1
3000
us
Raman shift, cm
cr
200
Fig. 2. Raman spectrum of the CVD monolayer grapheme.
an
Multilayer graphene could enhance the absolute modulation depth of the whole SA, but larger nonsaturable loss could be induced and easily accumulates more thermal energy in the SA, leading to a
M
lower damage threshold and finally limiting the available output power and pulse energy. However, monolayer graphene can provide very lower nonsaturable loss and a relatively higher damage threshold.
ed
3 Experiment setup
The experimental schematic of the laser is shown in Fig.3. This laser is pumped by a fiber-coupled laser diode array with a center wavelength of 808 nm. The pump light is collimated and focused by focusing optics
ce pt
to a Nd:YAG crystal. The Nd:YAG crystal has a dimension of Ф3 mm × 5 mm and a Nd3+ doping concentration of 0.5 at.%. The left face (M1) of the crystal has coated antireflection at 808 nm and high reflectivity at lasing wavelength. M2 is the output coupler, which has a transmission of 25% at 1064nm. The monolayer graphene is fabricated by the CVD method, and then transferred onto the facet of SiO2 for
Ac
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
constructing a SA. The Nd:YAG crystal and the SA are mounted in a copper heat sink to maintain the temperature around 20 oC.
Fig. 3. Setup of the monolayer graphene-based passively Q-switched Nd:YAG laser.
4 Experiment results and discussion Page 3 of 7
Without introducing monolayer graphene into the cavity, the laser operates in the continuous wave (CW) operation regime and starts to oscillate at a threshold value of 0.3 W. The maximum CW output power linearly increased up to 1.4 W under the pump power of 3 W. The overall optical-optical conversion efficiency is about 47%. Then we insert the graphene sample into the resonant cavity and adjust the cavity and the position of the SA finely. A stable Q-switched operation is achieved. Due to the introduction of optical loss from the SA, the threshold power increased up to 1 W. And the average output power increases
ip t
quasi-linearly up to 266 mW at a pump power of 3 W.
1.4
Q-switched
us
1.0 0.8 0.6 0.4 0.2 0.0 1.0
1.5
2.0
2.5
3.0
M
0.5
an
Output power, W
cr
CW
1.2
Pump Power, W
ed
Fig. 4. Relation between the output power and the pump power for CW and Q-switched operation.
The corresponding oscilloscope traces of the Q-switched pulse at the pump power 2.5 W and 3 W are
ce pt
shown in Fig. 5 and 6. The repetition rates are 374 kHz and 436 kHz, respectively. The pulse widths are 1005 ns and 753 ns, respectively. When the laser is Q-switched operation, there are no obvious modulations for the pulse, and the laser output power is stable. When the pump power exceeds 3.5 W, the Q-switched pulses become unstable and even disappeared (as shown in Fig. 7.). However, the Q-switched pulsed could be rebuilt once the pump power is less than 3.5 W again, which indicates no damage in
Ac
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
monolayer graphene. It can be attributed to the thermal effect affecting of the graphene.
Fig. 5. Oscilloscope trace of stable Q-Switched laser pulsed when pump power is 2.5 W. The pulse repetition rate is 374 kHz, and the pulse width is 1005 ns.
Page 4 of 7
ip t
Fig. 6. Oscilloscope trace of stable Q-Switched laser pulsed when pump power is 3 W. The pulse repetition rate is 436 kHz,
ed
M
an
us
cr
and the pulse width is 753 ns.
Fig.7. Oscilloscope trace of unstable Q-Switched laser pulsed when pump power is larger than 3.5 W.
ce pt
The dependence of the pulse duration and the repetition rate is shown in Fig. 8. The pulse width decreases from 1750 to 753 ns while the repetition rate increases from 140 to 436 kHz as the incident power varies from 1 to 3 W.
Pulse width, us
Ac
450
1.8
Pulse width Repetition pate
400
1.6
350 1.4 300 1.2 250 1.0
200
Repetition Pate, kHz
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
0.8
150 100
0.6 1.0
1.5
2.0
2.5
3.0
Pump power, W
Fig. 8. Pulsed width and repetition rate versus the pump power for the Q-switched operation.
Page 5 of 7
5 Conclusion In summary, We have demonstrated a pulsed Nd:YAG laser Q-switched by a monolayer graphene. The monolayer graphene is fabricated by the chemical vapor deposition (CVD) method, and then transferred onto the facet of SiO2 to construct a saturable absorber (SA). The repetition rate can be changed from 140 to 436 kHz and the pulse duration can be narrowed from 1750 to 753 ns when the pump power is changed
ip t
from 1 to 3 W. At the pump power of 3 W, the largest average output power of 266 mW is obtained.
Acknowledgements
cr
This paper is supported by the Natural Science Foundation of Fujian Province of China, the Scientific
us
Research Fund of Fujian Provincial Education Department of China (JA13231), and the National Natural Science Foundation of China (11304259).
an
References
Opt. Commun. 281(24) (2008) 6065-6067.
M
[1] Hong-Yi Lin, Jin Guo, Da-Yong Ning, et al., LD end-pumped intracavity frequency doubled Yb:YAG laser,
[2] Hongyi Lin, Xianguo Meng, Yingchao Xu, et al., Parasitic oscillation in mid-infrared optical parametric
ed
generator based on PPMgLN, Optik 124(16) (2013) 2511-2513. [3] Zhenhua Yu, Yanrong Song, Xinzheng Dong, et al., Watt-level passively Q-switched double-cladding
ce pt
fiber laser based on graphene oxide saturable absorber, Appl. Opt. 52(29) (2013) 7127-7131. [4] L. Q. Zhang, Z. Zhuo, J. X. Wang, et al., Passively Q-switched fiber laser based on graphene saturable absorber, Laser Phys. 22(2) (2012) 433-436. [5] Mengmeng Han, Shumin Zhang, Xingliang Li, et al., High-energy, tunable-wavelengths, Q-switched pulse laser, Opt. Commun. 326(1) (2014) 24-28.
Ac
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
[6] Shuo Han, Xianlei Li, Honghao Xu, et al., Graphene Q-switched 0.9-μm Nd:La0.11Y0.89VO4 laser, Chin. Opt. Lett. 12(1) (2014) 011401. [7] K.S. Novoselov, A.K. Geim, S.V. Morozov, et al., Electric field effect in atomically thin carbon films, Science 306 (5296) (2004) 666-669. [8] Duanduan Wu, Fengfu Xiong, Cankun Zhang, et al., Large-energy, wavelength-tunable, all-fiber passively Q-switched Er:Yb-codoped double-clad fiber laser with mono-layer chemical vapor deposition grapheme, Appl. Opt. 53(19) (2014) 4089-4093. [9]
Man
Jiang,
Zhaoyu
Ren,
Yuping
Zhang,
et
al.,
Graphene-based
passively
Q-switched
diode-side-pumped Nd:YAG solid laser, Opt. Commun. 284 (22) (2011) 5353-5356. Page 6 of 7
[10] Zhipei Sun, Tawfique Hasan, Felice Torrisi, et al., Graphene mode-locked ultrafast laser, ACS Nano. 4(2) (2010) 803-810. [11] Z C Tiu, F Ahmad, S J Tan, et al., Passive Q-switched Erbium-doped fiber laser with grapheme-polyethylene oxide saturable absorber in three different gain media, Indian J Phys. 88(7)
ip t
(2014) 727-731.
Corresponding author: School of Optoelectronic and Communication Engineering, Xiamen University of
cr
Technology, LiGong Road 600, JiMei District, Xiamen City, 360124, China. Tel.: +86 592 6291268.
ce pt
ed
M
an
us
E-mail address: [email protected] (H. Y. Lin).
Ac
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
Page 7 of 7
S0030-4026(15)01341-8 http://dx.doi.org/doi:10.1016/j.ijleo.2015.09.249 IJLEO 56454
To appear in: Received date: Accepted date:
4-12-2014 30-9-2015
Please cite this article as: H.-Y. Lin, X. Liu, X.-H. Huang, Y.-C. Xu, X.G. Meng, F.-B. Xiong, Monolayer graphene-based passively Q-switched Nd:YAG laser, Optik - International Journal for Light and Electron Optics (2015), http://dx.doi.org/10.1016/j.ijleo.2015.09.249 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
*Manuscript
Monolayer graphene-based passively Q-switched Nd:YAG laser Hong-Yi Lin a
a, b
c
, Xiao Liu , Xiao-Hua Huang
a, b
, Ying-Chao Xu
a, b
, Xian-Guo Meng
a, b
, Fei-Bing Xiong
a, b
School of Optoelectronic and Communication Engineering, Xiamen University of Technology, Xiamen 361024, China. b
Key Laboratory of Optoelectronic Technology, Fujian Province University, Xiamen 361024, China. c
School of Cultural Industries, Xiamen University of Technology, Xiamen 361024, China.
ip t
Abstract: We demonstrate a pulsed Nd:YAG laser Q-switched by a monolayer graphene. The monolayer graphene is fabricated by the chemical vapor deposition (CVD) method, and then transferred onto the facet
cr
of SiO2 to construct a saturable absorber (SA). The Q-switched largest output power of 266 mW, the maximum repetition rate of 436 kHz, and the narrowest pulse duration of 753 ns have been obtained when
us
the pump power is 3 W.
an
Key words: monolayer grapheme; passively Q-switched; Nd:YAG Laser; CVD.
1 Introduction
M
The Q-switched technique is a fundamental technique to generate high energy pulsed lasers, which are important for applications in the fields of laser processing, medicine, environmental sensing, telecommunications, range finding, material processing, and reflectometry [1, 2]. Unlike the mode-locked
ed
technique, the Q-switched technique has a relatively longer pulse duration and lower repetition rate (usually in the kHz range). Furthermore, Q-switching is able to produce higher pulse energies, higher operation
ce pt
efficiency, and more cost effective than mode-locking [3]. Q-switching can be obtained via one of two approaches, passive method or active method. The passively Q-switched method features a very simpler design and a more compact geometry compared to the active method. A
semiconductor saturable absorber mirror (SESAM) and Carbon nanotubes (CNTs) have been
Ac
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
successfully demonstrated to passively Q-switched lasers. However, the fabrication and packing of SESAMs requires very complex and costly processes. Moreover, the SESAM has a narrow wavelength working range for a laser. CNTs are a comparatively simple and cost effective alternative. Unfortunately, its operation wavelength is related to the diameter and chirality [4, 5]. Compared to SESAM and CNTs, graphene has its perfect optical characteristics, such as low cost, easy of fabrication, ultrafast recovery time, and a higher damage threshold, so it has been widely used to replace SESAM and CNTs [3-6].
2 Characteristics of Monolayer Graphene-based Saturable Absorber Graphene is a Dirac two-dimensional crystal of carbon atoms which arranges in a honeycomb lattice.
Page 1 of 7
Isolated grapheme nanosheets were firstly produced in 2004 by K. S. Novoselov, who wined the 2010 Nobel Prize of physics [7]. Graphene has very excellent linear and nonlinear optical properties, such as low nonsaturable loss, ultrafast recovery time (200 fs), and an ultrabroad wavelength independent saturable absorption range, which covers the laser wavelength range from the visible, infrared to terahertz wavelength region and shows little wavelength dependence [8]. The cause for saturable absorption of graphene is due to Pauli blocking. The conduction band and
ip t
valence band of graphene intersect at the Dirac point. Because graphene has a zero bandgap, it can absorb all photons ranging from the visible to terahertz wavelength region and show little wavelength dependence
cr
[9]. The photonic characteristics of graphene are significant shown in Fig. 1. If low intensity light incident,
us
photons are highly absorbed, and the electrons in the valence band will be excited up to conduction band of the graphene SA material. However, if high intensity light incident, according to the Pauli blocking principle, the conduction band will be filled easily and some photons are not absorbed. Therefore, only high intensity
ed
M
an
light can pass through the SA with very low loss and vice versa.
1064 nm
ce pt
4I 11/2
Fig.1. The characteristics of graphene SA material.
The Raman spectrum of the CVD monolayer grapheme is shown in Fig. 2, and it exhibits the prominent
Ac
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
peaks at Raman shift of approximately 1329, 1564, and 2681 cm-1, generally known as D, G, and 2D band, respectively. D band is associated with vibrations of carbon atoms with sp3 electronic configuration of disordered graphite. G-band contributes to an E2g mode of graphite and is related to the in-plane vibration of sp2-bonded carbon atoms. The intensity ratio of the D and G bands is about 0.22, indicating few defects and good quality in graphene sample [8-10]. Intensity ratio between G and 2D peak can be used to reduce the number of layer. Single-layer grapheme has a low intensity ratio, usually lower than or close to 0.5; while multilayer graphene shows higher intensity ratio, usually larger than 1 [10]. As shown in Fig. 2, the G/2D peak ratio of 0.53 indicates that we obtain monolayer graphene. Besides that, another way to distinguish the monolayer from multilayer one is full-width half maximum (FWHM) of the 2D peak [11]. The FWHM of 2D Page 2 of 7
peak is smaller as the number of graphene layers decrease. As shown in Fig. 2, the FWHM of 2D peak is only 33 cm-1, it can be suggest that the graphene sample is monolayer [8]. 1800
2D
1600
1200
G
1000 800
ip t
Intensity , a. u.
1400
600 400
D 0 1000
1500
2000
2500
-1
3000
us
Raman shift, cm
cr
200
Fig. 2. Raman spectrum of the CVD monolayer grapheme.
an
Multilayer graphene could enhance the absolute modulation depth of the whole SA, but larger nonsaturable loss could be induced and easily accumulates more thermal energy in the SA, leading to a
M
lower damage threshold and finally limiting the available output power and pulse energy. However, monolayer graphene can provide very lower nonsaturable loss and a relatively higher damage threshold.
ed
3 Experiment setup
The experimental schematic of the laser is shown in Fig.3. This laser is pumped by a fiber-coupled laser diode array with a center wavelength of 808 nm. The pump light is collimated and focused by focusing optics
ce pt
to a Nd:YAG crystal. The Nd:YAG crystal has a dimension of Ф3 mm × 5 mm and a Nd3+ doping concentration of 0.5 at.%. The left face (M1) of the crystal has coated antireflection at 808 nm and high reflectivity at lasing wavelength. M2 is the output coupler, which has a transmission of 25% at 1064nm. The monolayer graphene is fabricated by the CVD method, and then transferred onto the facet of SiO2 for
Ac
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
constructing a SA. The Nd:YAG crystal and the SA are mounted in a copper heat sink to maintain the temperature around 20 oC.
Fig. 3. Setup of the monolayer graphene-based passively Q-switched Nd:YAG laser.
4 Experiment results and discussion Page 3 of 7
Without introducing monolayer graphene into the cavity, the laser operates in the continuous wave (CW) operation regime and starts to oscillate at a threshold value of 0.3 W. The maximum CW output power linearly increased up to 1.4 W under the pump power of 3 W. The overall optical-optical conversion efficiency is about 47%. Then we insert the graphene sample into the resonant cavity and adjust the cavity and the position of the SA finely. A stable Q-switched operation is achieved. Due to the introduction of optical loss from the SA, the threshold power increased up to 1 W. And the average output power increases
ip t
quasi-linearly up to 266 mW at a pump power of 3 W.
1.4
Q-switched
us
1.0 0.8 0.6 0.4 0.2 0.0 1.0
1.5
2.0
2.5
3.0
M
0.5
an
Output power, W
cr
CW
1.2
Pump Power, W
ed
Fig. 4. Relation between the output power and the pump power for CW and Q-switched operation.
The corresponding oscilloscope traces of the Q-switched pulse at the pump power 2.5 W and 3 W are
ce pt
shown in Fig. 5 and 6. The repetition rates are 374 kHz and 436 kHz, respectively. The pulse widths are 1005 ns and 753 ns, respectively. When the laser is Q-switched operation, there are no obvious modulations for the pulse, and the laser output power is stable. When the pump power exceeds 3.5 W, the Q-switched pulses become unstable and even disappeared (as shown in Fig. 7.). However, the Q-switched pulsed could be rebuilt once the pump power is less than 3.5 W again, which indicates no damage in
Ac
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
monolayer graphene. It can be attributed to the thermal effect affecting of the graphene.
Fig. 5. Oscilloscope trace of stable Q-Switched laser pulsed when pump power is 2.5 W. The pulse repetition rate is 374 kHz, and the pulse width is 1005 ns.
Page 4 of 7
ip t
Fig. 6. Oscilloscope trace of stable Q-Switched laser pulsed when pump power is 3 W. The pulse repetition rate is 436 kHz,
ed
M
an
us
cr
and the pulse width is 753 ns.
Fig.7. Oscilloscope trace of unstable Q-Switched laser pulsed when pump power is larger than 3.5 W.
ce pt
The dependence of the pulse duration and the repetition rate is shown in Fig. 8. The pulse width decreases from 1750 to 753 ns while the repetition rate increases from 140 to 436 kHz as the incident power varies from 1 to 3 W.
Pulse width, us
Ac
450
1.8
Pulse width Repetition pate
400
1.6
350 1.4 300 1.2 250 1.0
200
Repetition Pate, kHz
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65
0.8
150 100
0.6 1.0
1.5
2.0
2.5
3.0
Pump power, W
Fig. 8. Pulsed width and repetition rate versus the pump power for the Q-switched operation.
Page 5 of 7
5 Conclusion In summary, We have demonstrated a pulsed Nd:YAG laser Q-switched by a monolayer graphene. The monolayer graphene is fabricated by the chemical vapor deposition (CVD) method, and then transferred onto the facet of SiO2 to construct a saturable absorber (SA). The repetition rate can be changed from 140 to 436 kHz and the pulse duration can be narrowed from 1750 to 753 ns when the pump power is changed
ip t
from 1 to 3 W. At the pump power of 3 W, the largest average output power of 266 mW is obtained.
Acknowledgements
cr
This paper is supported by the Natural Science Foundation of Fujian Province of China, the Scientific
us
Research Fund of Fujian Provincial Education Department of China (JA13231), and the National Natural Science Foundation of China (11304259).
an
References
Opt. Commun. 281(24) (2008) 6065-6067.
M
[1] Hong-Yi Lin, Jin Guo, Da-Yong Ning, et al., LD end-pumped intracavity frequency doubled Yb:YAG laser,
[2] Hongyi Lin, Xianguo Meng, Yingchao Xu, et al., Parasitic oscillation in mid-infrared optical parametric
ed
generator based on PPMgLN, Optik 124(16) (2013) 2511-2513. [3] Zhenhua Yu, Yanrong Song, Xinzheng Dong, et al., Watt-level passively Q-switched double-cladding
ce pt
fiber laser based on graphene oxide saturable absorber, Appl. Opt. 52(29) (2013) 7127-7131. [4] L. Q. Zhang, Z. Zhuo, J. X. Wang, et al., Passively Q-switched fiber laser based on graphene saturable absorber, Laser Phys. 22(2) (2012) 433-436. [5] Mengmeng Han, Shumin Zhang, Xingliang Li, et al., High-energy, tunable-wavelengths, Q-switched pulse laser, Opt. Commun. 326(1) (2014) 24-28.
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[6] Shuo Han, Xianlei Li, Honghao Xu, et al., Graphene Q-switched 0.9-μm Nd:La0.11Y0.89VO4 laser, Chin. Opt. Lett. 12(1) (2014) 011401. [7] K.S. Novoselov, A.K. Geim, S.V. Morozov, et al., Electric field effect in atomically thin carbon films, Science 306 (5296) (2004) 666-669. [8] Duanduan Wu, Fengfu Xiong, Cankun Zhang, et al., Large-energy, wavelength-tunable, all-fiber passively Q-switched Er:Yb-codoped double-clad fiber laser with mono-layer chemical vapor deposition grapheme, Appl. Opt. 53(19) (2014) 4089-4093. [9]
Man
Jiang,
Zhaoyu
Ren,
Yuping
Zhang,
et
al.,
Graphene-based
passively
Q-switched
diode-side-pumped Nd:YAG solid laser, Opt. Commun. 284 (22) (2011) 5353-5356. Page 6 of 7
[10] Zhipei Sun, Tawfique Hasan, Felice Torrisi, et al., Graphene mode-locked ultrafast laser, ACS Nano. 4(2) (2010) 803-810. [11] Z C Tiu, F Ahmad, S J Tan, et al., Passive Q-switched Erbium-doped fiber laser with grapheme-polyethylene oxide saturable absorber in three different gain media, Indian J Phys. 88(7)
ip t
(2014) 727-731.
Corresponding author: School of Optoelectronic and Communication Engineering, Xiamen University of
cr
Technology, LiGong Road 600, JiMei District, Xiamen City, 360124, China. Tel.: +86 592 6291268.
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E-mail address: [email protected] (H. Y. Lin).
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