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Passively Q-switched Nd:YAG laser at 1074.1 nm
Journal Pre-proof Passively Q-switched Nd:YAG laser at 1074.1 nm Hong-Yi Lin, Xiao-Hua Huang, Hong Liu
PII:
S0030-4026(19)31729-2
DOI:
https://doi.org/10.1016/j.ijleo.2019.163831
Reference:
IJLEO 163831
To appear in:
Optik
Received Date:
7 September 2019
Accepted Date:
19 November 2019
Please cite this article as: Lin H-Yi, Huang X-Hua, Liu H, Passively Q-switched Nd:YAG laser at 1074.1 nm, Optik (2019), doi: https://doi.org/10.1016/j.ijleo.2019.163831
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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. © 2019 Published by Elsevier.
Passively Q-switched Nd:YAG laser at 1074.1 nm Hong-Yi Lina,b*, Xiao-Hua Huanga,b, Hong Liua aSchool
of Optoelectronic and Communication Engineering, Xiamen University of Technology, Xiamen, China
bFujian
Key Laboratory of Optoelectronic Technology and Devices, Xiamen University of Technology, Xiamen, China
Abstract: We report a passively Q-switched Nd:YAG laser at 1074.1 nm based on an elaborate plane-plane cavity. By optimizing coatings of the cavity, the fierce parasitic transitions at 1064, 1112 and 1123 nm are suppressed, and the line at 1074 nm is individually amplified. The CW power of 1480 mW at 1074.1 nm is achieved at a pump power of 10.0 W. The single-wavelength line at 1074.1 nm in the passively Q-switched regime is obtained and produces stable pulses as short as 23.7 ns with peak power of 1584 W.
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Keywords: Nd:YAG laser; 1074.1 nm laser; Q-switched.
1. Introduction
For all-solid-state lasers, Nd:YAG crystal is one of the most popular and efficient luminescent media due to its admirable mechanical, physical and optical characteristics [1-3].The Nd:YAG has greater than 10 lines between 900
-p
and 1400 nm in Figure 1. Mostly, the Nd:YAG laser works at some particular wavelengths, such as 946 nm, 1.1 μm and 1.3 μm, which correspond the three transitions of 4F3/2 → 4I9/2, 4F3/2 → 4I11/2, and 4F3/2 → 4I13/2, respectively [4, 5].
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Among these spectrums, the 4F3/2 → 4I11/2 at 1.1 μm is the most popular and effective, and it has six or seven peak lines (i.e., 1052, 1064, 1074, 1112, and 1123 nm) due to the different Stark levels [5-7]. The emission cross-sections at 1074, 1112, and 1123 nm are 1.63 × 10-19, 0.36 × 10-19 and 0.30 × 10-19 cm2, lower than that of the line at 1064 nm,
lP
respectively. There are many ways to restrain the oscillation at 1064 nm, such as inserting prism or etalon into cavity, using special grating to replace the output mirror, and well-designed cavity coating to increase loss at 1064 nm [4]. In this paper, by intelligent design the cavity coatings, the fierce transition at 1064, 1112 or 1123 nm can be eliminated,
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and the low-gain line at 1074 nm is amplified.
2. Experimental details and analysis
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Figure 2 shows an experimental schematic of the 1074.1 nm laser. The Nd:YAG cuboids (Crystech Inc., 1.1 at. % Nd3+) with dimensions of 3 × 3 × 5 mm3 is excited by an 807.8 nm fiber-coupled LD (Focuslight In.). The left surface (M1) of the crystal has high transmission (HT) coating at 808, 946 and 1064 nm while it is high reflection (HR) coated
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at 1074 nm in Figure 3.
The reflectivities at 946, 1064, 1074, 1112, 1123, 1319 and 1338 nm are 0.6%, 3.7%, 96.1%, 98.7%, 98.7%, 87.5% and 87.5%, respectively. M2 is a flat output mirror with a part-transmission (PT) coating at 1074 nm and HT coating at 1319 nm. The reflectivities of M2 at 946, 1064, 1074, 1112, 1123, 1319 and 1338 nm are 60%, 80%, 80%, 82%, 82%, 12% and 12%, respectively. The 1074 nm Nd:YAG laser is passively Q-switched by a Cr:YAG with the initial transmission of 89.5%. Both the facets of the Cr:YAG and the right surface of the Nd:YAG are HT coated at 1064 and 1074 nm. The pump threshold ratio is achieved [8] and the result is displayed in Table 1. The threshold ratio at 1074, 946, 1064, 1112, 1123, 1319 and 1318 nm is Pth,1074 : Pth,946 : Pth,1064 : Pth,1112 : Pth,1123 : Pth,1319 : Pth,1338 =1.0 : 59.2 : 4.6 : 3.8 : 4.6 : 17.8 : 17.1. The line at 1074 nm has the smallest threshold, and it can oscillate solely and efficiently. Meanwhile,
The line at 1074 nm has weaker the emission cross-section, nearly 35.6% of that at 1064 nm, and it is more appropriate to passively Q-switched by the Cr:YAG crystal.
3. Results and discussion In the CW regime, the threshold is about 3.2 W in Figure 4. When the pump power reaches 10.0 W, the output power at 1074.1 nm is 1480 mW, and the optical-optical and slop conversion efficiencies are 14.8% and 21.3%, respectively. The output spectrum is detected in Figure 5 and there is only a single-line at 1074.12 nm at the different pump powers. The other lines at 946, 1053, 1064, 1112, 1123, 1319 and 1338 nm are completely suppressed. When the Cr:YAG is used, the pulse at 1074.1 nm is generated. The pulse threshold reaches up to 4.6 W and the 1074.1 nm power drops to 822 mW due to insertion loss. We observe the pulse width and repetition rate in Figure 6 and calculate the pulse energy and peak power in Figure 7. By increasing pump power from 5.3 W to 10.0 W, the repetition rate is tuned from 4.3 kHz to 21.9 kHz, the pulse energy increases from 32.8 μJ to 38.5 μJ and then slightly decreases down to 37.5 μJ, and the pulse width represents minor variations between 24.6 ns and 23.7 ns. The narrowest pulse
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width, the largest repetition rate, the strongest pulse energy and the highest peak power are 23.7 ns, 21.9 kHz, 38.5 μJ and 1584 W, respectively. Figure 8 shows the pulse train (a) of 21.9 kHz and pulse shape (b) of 23.7 ns at the pump power of 10.0 W.
-p
4. Conclusion
A CW and pulse 1074.1 nm Nd:YAG laser passively Q-switched by a Cr:YAG crystal is achieved based on a elaborate cavity. By optimizing reflection coatings of the cavity, the parasitic lines at 946, 1052, 1064, 1112, 1123, 1319
re
and 1338 nm are suppressed completely and the single-line at 1074 nm is oscillated. The passively Q-switched Nd:YAG laser at 1074.1 nm is generated for the fist time. The largest peak power and the smallest pulse width are 1584 W and
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23.7 ns, respectively. It is possible to use an input mirror (M1) that has higher reflectivity at 1074 nm (e.g., 99.5%) to decline the pulse width and augment the peak power gradually.
Acknowledgments
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This paper is sponsored by National Natural Science Foundation of China (11094304).
References
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[1] H.C. Lee, Y.P. Kim, Opt. Commun. 281 (2008) 4455-4458. [2] H.-Y. Lin, H. Liu, Y.-P. Wang, Optik 147 (2017) 123-127. [3] N.N. Adnan, N. Bidin, N.A.M. Taib, H. Haris, M. Fakaruddin, A.M. Hashim, G. Krishnan, S.W. Harun, Opt. Laser Technol. 80 (2016)
Jo
28-32.
[4] Z. Lin, X. Huang, J. Lan, Y. Cheng, Y. Wang, B. Xu, H. Xu, Z. Cai, IEEE Photonics 8 (2016) 1500808. [5] L. Chen, Z. Wang, S. Zhuang, H. Yu, Y. Zhao, L. Guo, X. Xu, Opt. Lett. 36 (2011) 2554-2556. [6] M. He, F. Yang, Z.-C. Wang, H.-W. Gao, L. Yuan, C.-L. Li, N. Zong, Y. Shen, Y. Bo, Q.-J. Peng, D.-F. Cui, Z.-Y. Xu, Opt. Laser Technol. 103 (2018) 77-81. [7] Z. Wang, X. Wang, M. Cai, Y. Bu, L. Chen, G. Cai, Opt. Commun. 330 (2014) 143-146. [8] H. Lin, H. Liu, X. Huang, N. Copner, D. Sun, J. Mod. Opt. 25 (2018) 423-426.
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Fig. 1. The spectra of the 1.1 at% Nd:YAG crystal (Edinburch Instruments FLS 980).
M2 Cr:YAG
M1 Nd:YAG
808 LD Focusing lens PT @ 1074 nm HT @ 808 and 1064 nm HT @ 1074 nm (T = 20%) HR @1074 nm
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Fig. 2. The configuration of the 1074.1 nm laser.
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Fig. 3. The reflectivity of the right facet M1 at 700 - 1200 nm.
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Fig. 4. The output power at 1074.1 nm.
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Fig. 5. The spectrum at 1074.1 nm.
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Fig. 6. The repetition rate and pulse width at 1074.1 nm.
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Fig. 7. The pulse energy and peak power at 1074.1 nm.
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Fig. 8. The pulse train (a) and pulse shape (b) at 1074.1 nm.
Table 1. The important parameters of the 1074.1 nm laser.
Wavelength (nm)
Emission Cross-section
M1 Reflectivity (%)
(10-19 cm2)
M2 Reflectivity (%)
Quantum Efficiency (%)
Threshold Ratio
1.63
96.1
80
75.2
1.0
946
0.51
0.6
60
85.4
59.2
1064
4.58
3.7
80
75.9
4.6
1112
0.36
98.7
82
72.7
3.8
1123
0.30
98.7
82
71.9
4.6
1319
0.95
87.5
12
61.2
17.8
1338
1.00
87.5
12
60.4
17.1
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1074
PII:
S0030-4026(19)31729-2
DOI:
https://doi.org/10.1016/j.ijleo.2019.163831
Reference:
IJLEO 163831
To appear in:
Optik
Received Date:
7 September 2019
Accepted Date:
19 November 2019
Please cite this article as: Lin H-Yi, Huang X-Hua, Liu H, Passively Q-switched Nd:YAG laser at 1074.1 nm, Optik (2019), doi: https://doi.org/10.1016/j.ijleo.2019.163831
This is a PDF file of an article that has undergone enhancements after acceptance, such as the addition of a cover page and metadata, and formatting for readability, but it is not yet the definitive version of record. This version will undergo additional copyediting, typesetting and review before it is published in its final form, but we are providing this version to give early visibility of the article. 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. © 2019 Published by Elsevier.
Passively Q-switched Nd:YAG laser at 1074.1 nm Hong-Yi Lina,b*, Xiao-Hua Huanga,b, Hong Liua aSchool
of Optoelectronic and Communication Engineering, Xiamen University of Technology, Xiamen, China
bFujian
Key Laboratory of Optoelectronic Technology and Devices, Xiamen University of Technology, Xiamen, China
Abstract: We report a passively Q-switched Nd:YAG laser at 1074.1 nm based on an elaborate plane-plane cavity. By optimizing coatings of the cavity, the fierce parasitic transitions at 1064, 1112 and 1123 nm are suppressed, and the line at 1074 nm is individually amplified. The CW power of 1480 mW at 1074.1 nm is achieved at a pump power of 10.0 W. The single-wavelength line at 1074.1 nm in the passively Q-switched regime is obtained and produces stable pulses as short as 23.7 ns with peak power of 1584 W.
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Keywords: Nd:YAG laser; 1074.1 nm laser; Q-switched.
1. Introduction
For all-solid-state lasers, Nd:YAG crystal is one of the most popular and efficient luminescent media due to its admirable mechanical, physical and optical characteristics [1-3].The Nd:YAG has greater than 10 lines between 900
-p
and 1400 nm in Figure 1. Mostly, the Nd:YAG laser works at some particular wavelengths, such as 946 nm, 1.1 μm and 1.3 μm, which correspond the three transitions of 4F3/2 → 4I9/2, 4F3/2 → 4I11/2, and 4F3/2 → 4I13/2, respectively [4, 5].
re
Among these spectrums, the 4F3/2 → 4I11/2 at 1.1 μm is the most popular and effective, and it has six or seven peak lines (i.e., 1052, 1064, 1074, 1112, and 1123 nm) due to the different Stark levels [5-7]. The emission cross-sections at 1074, 1112, and 1123 nm are 1.63 × 10-19, 0.36 × 10-19 and 0.30 × 10-19 cm2, lower than that of the line at 1064 nm,
lP
respectively. There are many ways to restrain the oscillation at 1064 nm, such as inserting prism or etalon into cavity, using special grating to replace the output mirror, and well-designed cavity coating to increase loss at 1064 nm [4]. In this paper, by intelligent design the cavity coatings, the fierce transition at 1064, 1112 or 1123 nm can be eliminated,
na
and the low-gain line at 1074 nm is amplified.
2. Experimental details and analysis
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Figure 2 shows an experimental schematic of the 1074.1 nm laser. The Nd:YAG cuboids (Crystech Inc., 1.1 at. % Nd3+) with dimensions of 3 × 3 × 5 mm3 is excited by an 807.8 nm fiber-coupled LD (Focuslight In.). The left surface (M1) of the crystal has high transmission (HT) coating at 808, 946 and 1064 nm while it is high reflection (HR) coated
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at 1074 nm in Figure 3.
The reflectivities at 946, 1064, 1074, 1112, 1123, 1319 and 1338 nm are 0.6%, 3.7%, 96.1%, 98.7%, 98.7%, 87.5% and 87.5%, respectively. M2 is a flat output mirror with a part-transmission (PT) coating at 1074 nm and HT coating at 1319 nm. The reflectivities of M2 at 946, 1064, 1074, 1112, 1123, 1319 and 1338 nm are 60%, 80%, 80%, 82%, 82%, 12% and 12%, respectively. The 1074 nm Nd:YAG laser is passively Q-switched by a Cr:YAG with the initial transmission of 89.5%. Both the facets of the Cr:YAG and the right surface of the Nd:YAG are HT coated at 1064 and 1074 nm. The pump threshold ratio is achieved [8] and the result is displayed in Table 1. The threshold ratio at 1074, 946, 1064, 1112, 1123, 1319 and 1318 nm is Pth,1074 : Pth,946 : Pth,1064 : Pth,1112 : Pth,1123 : Pth,1319 : Pth,1338 =1.0 : 59.2 : 4.6 : 3.8 : 4.6 : 17.8 : 17.1. The line at 1074 nm has the smallest threshold, and it can oscillate solely and efficiently. Meanwhile,
The line at 1074 nm has weaker the emission cross-section, nearly 35.6% of that at 1064 nm, and it is more appropriate to passively Q-switched by the Cr:YAG crystal.
3. Results and discussion In the CW regime, the threshold is about 3.2 W in Figure 4. When the pump power reaches 10.0 W, the output power at 1074.1 nm is 1480 mW, and the optical-optical and slop conversion efficiencies are 14.8% and 21.3%, respectively. The output spectrum is detected in Figure 5 and there is only a single-line at 1074.12 nm at the different pump powers. The other lines at 946, 1053, 1064, 1112, 1123, 1319 and 1338 nm are completely suppressed. When the Cr:YAG is used, the pulse at 1074.1 nm is generated. The pulse threshold reaches up to 4.6 W and the 1074.1 nm power drops to 822 mW due to insertion loss. We observe the pulse width and repetition rate in Figure 6 and calculate the pulse energy and peak power in Figure 7. By increasing pump power from 5.3 W to 10.0 W, the repetition rate is tuned from 4.3 kHz to 21.9 kHz, the pulse energy increases from 32.8 μJ to 38.5 μJ and then slightly decreases down to 37.5 μJ, and the pulse width represents minor variations between 24.6 ns and 23.7 ns. The narrowest pulse
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width, the largest repetition rate, the strongest pulse energy and the highest peak power are 23.7 ns, 21.9 kHz, 38.5 μJ and 1584 W, respectively. Figure 8 shows the pulse train (a) of 21.9 kHz and pulse shape (b) of 23.7 ns at the pump power of 10.0 W.
-p
4. Conclusion
A CW and pulse 1074.1 nm Nd:YAG laser passively Q-switched by a Cr:YAG crystal is achieved based on a elaborate cavity. By optimizing reflection coatings of the cavity, the parasitic lines at 946, 1052, 1064, 1112, 1123, 1319
re
and 1338 nm are suppressed completely and the single-line at 1074 nm is oscillated. The passively Q-switched Nd:YAG laser at 1074.1 nm is generated for the fist time. The largest peak power and the smallest pulse width are 1584 W and
lP
23.7 ns, respectively. It is possible to use an input mirror (M1) that has higher reflectivity at 1074 nm (e.g., 99.5%) to decline the pulse width and augment the peak power gradually.
Acknowledgments
na
This paper is sponsored by National Natural Science Foundation of China (11094304).
References
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[1] H.C. Lee, Y.P. Kim, Opt. Commun. 281 (2008) 4455-4458. [2] H.-Y. Lin, H. Liu, Y.-P. Wang, Optik 147 (2017) 123-127. [3] N.N. Adnan, N. Bidin, N.A.M. Taib, H. Haris, M. Fakaruddin, A.M. Hashim, G. Krishnan, S.W. Harun, Opt. Laser Technol. 80 (2016)
Jo
28-32.
[4] Z. Lin, X. Huang, J. Lan, Y. Cheng, Y. Wang, B. Xu, H. Xu, Z. Cai, IEEE Photonics 8 (2016) 1500808. [5] L. Chen, Z. Wang, S. Zhuang, H. Yu, Y. Zhao, L. Guo, X. Xu, Opt. Lett. 36 (2011) 2554-2556. [6] M. He, F. Yang, Z.-C. Wang, H.-W. Gao, L. Yuan, C.-L. Li, N. Zong, Y. Shen, Y. Bo, Q.-J. Peng, D.-F. Cui, Z.-Y. Xu, Opt. Laser Technol. 103 (2018) 77-81. [7] Z. Wang, X. Wang, M. Cai, Y. Bu, L. Chen, G. Cai, Opt. Commun. 330 (2014) 143-146. [8] H. Lin, H. Liu, X. Huang, N. Copner, D. Sun, J. Mod. Opt. 25 (2018) 423-426.
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Fig. 1. The spectra of the 1.1 at% Nd:YAG crystal (Edinburch Instruments FLS 980).
M2 Cr:YAG
M1 Nd:YAG
808 LD Focusing lens PT @ 1074 nm HT @ 808 and 1064 nm HT @ 1074 nm (T = 20%) HR @1074 nm
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Fig. 2. The configuration of the 1074.1 nm laser.
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Fig. 3. The reflectivity of the right facet M1 at 700 - 1200 nm.
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Fig. 4. The output power at 1074.1 nm.
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Fig. 5. The spectrum at 1074.1 nm.
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Fig. 6. The repetition rate and pulse width at 1074.1 nm.
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Fig. 7. The pulse energy and peak power at 1074.1 nm.
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Fig. 8. The pulse train (a) and pulse shape (b) at 1074.1 nm.
Table 1. The important parameters of the 1074.1 nm laser.
Wavelength (nm)
Emission Cross-section
M1 Reflectivity (%)
(10-19 cm2)
M2 Reflectivity (%)
Quantum Efficiency (%)
Threshold Ratio
1.63
96.1
80
75.2
1.0
946
0.51
0.6
60
85.4
59.2
1064
4.58
3.7
80
75.9
4.6
1112
0.36
98.7
82
72.7
3.8
1123
0.30
98.7
82
71.9
4.6
1319
0.95
87.5
12
61.2
17.8
1338
1.00
87.5
12
60.4
17.1
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1074