- Email: [email protected]
PPMgLN green laser
Optik - International Journal for Light and Electron Optics xxx (xxxx) xxxx
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.com/locate/ijleo
Original research article
Compact CW Nd:YVO4/PPMgLN green laser Hong-Yi Lina,b,*, Xiao-Hua Huanga,b, Dong Suna,b, Lu-Ming Songa, Ji-Yan Zhanga,b a b
School of Optoelectronic and Communication Engineering, Xiamen University of Technology, Xiamen, 361024, China Fujian Key Laboratory of Optoelectronic Technology and Devices, Xiamen University of Technology, Xiamen, 361024, China
A R T IC LE I N F O
ABS TRA CT
Keywords: Green laser Nd:YVO4 laser PPMgLN
A compact and reliable linear-beam Nd:YVO4/PPMgLN green laser pumped by an edge-emitting laser diode array (24 separate emitters with an overall length of 480 μm and a gross power of 45 W at 807.1 nm) is achieved. The independent 24-edge-emitting array can achieve poor spatial coherence and effectively reduce laser speckle effect. In the air-cooled (water-cooled) condition, the maximum output power is 8.64 W (11.10 W), the optical-optical conversion efficiency is 24 % (25 %), and the power variation is less than 3 % (2 %) for 1 h (3 h).
1. Introduction The green lasers produced by frequency doubling technology have some advantages of stable performance, high efficiency and simple and compact structure. They are widely used in stage performance show, underwater communication, biomedical, laser display, 3D holographic display and other fields [1]. For the laser display, the main direction is to improve power and efficiency, reduce volume and power consumption, especially reduce coherence and eliminate laser speckle as far as possible. For 3D holographic display, the main direction is to reduce spectral line-width, enhance coherence (coherence length of several ten meters), optimize beam quality, improve power, reduce volume and realize direct high-speed modulation. Different requirements in the various fields have promoted the further development of the green lasers [2–4]. Here, we report a compact and reliable linear-beam Nd:YVO4/PPMgLN green laser pumped by an edge-emitting laser diode array and the maximum green power at 532.2 nm reaches 11.10 W. 2. Properties of the PPMgLN crystal KTP, LBO, LN, BBO and LT are the traditional non-linear crystals used for frequency doubling. In order to obtain high efficiency output, strict angular-phase-matching must be satisfied. The appearance of quasi-phase-matched periodically polarized crystals has greatly promoted the development of frequency doubling technology. Quasi-phase-matching makes full use of the maximum nonlinear coefficient of crystals, eliminates the walk-off effect and improves the conversion efficiency [5,6]. The commonly used periodically polarized crystals are PPLN, PPLT, PPKTP, PPMgLN, etc. Compared with PPLN and PPKTP, PPMgLN has a higher threshold of light damage resistance, and can achieve high efficiency at room temperature. The PPMgLT crystal has a small absorption coefficient, which is the best choice for several hundred watts green lasers. However, for low power green lasers, PPMgLN crystal is the best choice. The higher nonlinearity coefficient (16–22 pm/V) of PPMgLN reduces the requirement of fundamental laser power and improves the efficiency. Ref. [9] points out when the length of PPMgLN crystal is 2 mm, the temperature bandwidth and wavelength acceptance linewidth
⁎
Corresponding author at: School of Optoelectronic and Communication Engineering, Xiamen University of Technology, Xiamen, 361024, China. E-mail address: [email protected] (H.-Y. Lin).
https://doi.org/10.1016/j.ijleo.2019.163841 Received 9 September 2019; Accepted 20 November 2019 0030-4026/ © 2019 Elsevier GmbH. All rights reserved.
Please cite this article as: Hong-Yi Lin, et al., Optik - International Journal for Light and Electron Optics, https://doi.org/10.1016/j.ijleo.2019.163841
Optik - International Journal for Light and Electron Optics xxx (xxxx) xxxx
H.-Y. Lin, et al.
Fig. 1. Temperature acceptance bandwidth and wavelength acceptance linewidth versus the length of the PPMgLN crystal.
are 4.00 °C and 0.336 nm, respectively. However, when the length of PPMgLN crystal is 15 mm, the temperature bandwidth and wavelength acceptance linewidth reduce to 0.53 °C and 0.051 nm. Therefore, longer crystal has higher requirements on fundamental line-width, temperature control and mode matching. 3. Experimental setup There are two kinds of common frequency doubling structures: intra-cavity and single-pass external cavity. The output characteristics of the extra-cavity frequency doubling structure are more stable and reliable because the fundamental light and the nonlinear crystal are independent of each other. However, the fundamental light passes through PPMgLN crystal only once. In order to ensure the conversion efficiency, the length of PPMgLN crystal is generally longer (usually greater than 15 mm). On the other hand, the longer length of PPMgLN has, the lower the temperature bandwidth and fundamental linewidth of PPMgLN become (as shown in Fig. 1). Therefore, in order to take into account the conversion efficiency and compactness, most of the current frequency doubling technology has used the intracavity structure. The intracavity structure has the following advantages: 1) higher power of intracavity fundamental light reduces the requirement for the quality of fundamental beam; 2) compacter intracavity structure, easy to miniaturize, and even modular integration; 3) the intracavity structure reduces the requirement for PPMgLN length (usually 1−2 mm). Acceptance bandwidth is larger, which is easier to control temperature. In this paper, we use the intracavity structure in Fig. 2. The pump source (24 separate emitters with an overall length of 480 μm and a gross power of 45 W at 807.1 nm) and the Nd:YVO4 crystal (13 × 4 × 1.5 mm3 and 1.0 at. % Nd3+) are the same as the reference [2]. The input facet of the Nd:YVO4 crystal (Min) and the output coupler (Moc) are coated high-reflection (HR) at 1064.4 nm, the output facet of the Nd:YVO4 crystal is coated HR at 532.2 nm, and the both facets of the PPMgLN crystal and Moc are coated anti-reflection (AR) at 532.2 nm. The PPMgLN crystal (CTL Photonics) is 11 mm-wide, 1 mm-long and 1 mm-thick, and its polarization period is 6.95 μm. 4. Results In the air-cooled condition, the maximum output power is 8.64 W in Fig. 3, the optical-optical conversion efficiency is 24 %, and the power variation is less than 3 % for 1 h in Fig. 4. In order to improve the output power, thermal effect and power ability, a water-cooled radiator is used to control the Nd:YVO4
Fig. 2. The setup of the Nd:YVO4/PPMgLN laser. 2
Optik - International Journal for Light and Electron Optics xxx (xxxx) xxxx
H.-Y. Lin, et al.
Fig. 3. Output power in the air-cooled condition.
Fig. 4. Power stability for 1 h in the air-cooled condition.
and PPMgLN’s temperature. In the water-cooled condition, the maximum output power rises to 11.10 W at a pump power of 44.40 W in Fig. 5, the optical-optical conversion efficiency reaches 25 %, and the power variation is less than 2 % for 3 h. Table 1 lists output performances of multi-light-emitting arrayed LD-pumped green lasers at 532 nm [7–10]. We can see that, in contrast to other papers, the performance of our Nd:YVO4/PPMgLN green laser is very efficient and admirable. 5. Conclusion A compact and reliable linear-beam Nd:YVO4/PPMgLN green laser pumped by an edge-emitting laser diode array (24 separate emitters with an overall length of 480 μm and a gross power at 807.1 nm of 45 W) is achieved. In the water-cooled condition, the maximum output power is 11.10 W. The independent 24-edge-emitting array can efficiently reduce laser speckle effect and this green
Fig. 5. Output power in the water-cooled condition. 3
Optik - International Journal for Light and Electron Optics xxx (xxxx) xxxx
H.-Y. Lin, et al.
Table 1 Output performances of multi-light-emitting arrayed LD-pumped green lasers. (OO: optical-to-optical conversion efficiency; EO: electro-optical conversion efficiency). Research institute, Year
LD
PPMgLN
Output parameters
Mitsubishi Electric Corporation, Japan, 2008 [7]
15 arrayed LD
Mitsubishi Electric Corporation, Japan, 2009 [8]
15 arrayed LD
Planar-waveguide 4 mm Planar-waveguide
Mitsubishi Electric Corporation, Japan, 2009 [9]
15 arrayed LD
Chinese Academy of Sciences, 2016 [10] Here
19 arrayed LD 15 arrayed LD
Average power 7.6 W, Peak power 10.9 W, OO 40 %, EO 20 % CW 10.8 W, OO 40 %, EO 20 % Pulse, Peak power 11.4 W, Average power 3.8 W, OO 42 % CW 10.8 W, OO 40 %, EO 20 %, Temperature bandwidth 40 °C 3.12 W, OO 9.2 % CW air-cooled 8.64 W, OO 20 % CW water-cooled 11.10 W, OO 25 %
4 mm Planar-waveguide 4 mm 2 mm, 6.95 μm 1 mm, 6.95 μm
laser can be used in the laser display areas. Acknowledgments This paper is sponsored by the External Cooperation Program of Fujian Provincial Science and Technology Department (2018I0019), Scientific Research Fund of Fujian Provincial Education Department of China (JAT170409) and National Natural Science Foundation of China (11094304). References [1] [2] [3] [4] [5] [6] [7]
[8] [9] [10]
W.M. Yao, J. Gao, L. Zhang, J. Li, Y.B. Tian, Y.F. Ma, X.D. Wu, G.F. Ma, J.M. Yang, Y.B. Pan, X.J. Dai, Appl. Opt. 54 (2015) 5817–5821. H.-Y. Lin, M.-Y. Wu, J. Tang, D. Sun, Optik 192 (2019) 162951. J.-W. Xue, K. Li, Y.-J. Fang, H.-J. Xie, B.-H. Su, Laser J. 36 (2015) 20–23. O.B. Jensen, A.K. Hansen, A. Müller, B. Sumpf, P.M. Petersen, P.E. Andersen, Opt. Commun. 392 (2017) 167–170. J. Wei, H. Lu, P. Jin, K. Peng, Opt. Express 25 (2017) 3545–3552. T. Mochizuki, K. Kimura, Y. Maeda, K. Takahashi, N. Iwase, M. Oka, M. Saito, Advanced Solid-State Photonics, OSA Technical Digest Series (CD) (Optical Society of America, 2008), (2008) MG5. Y. Hirano, S. Yamamoto, Y. Koyata, M. Imaki, M. Okano, T. Hamaguchi, A. Nakamura, T. Yagi, T. Yanagisawa, Conference on Lasers and Electro-Optics/ Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies, OSA Technical Digest (CD) (Optical Society of America), 2008 CPDA3. Y. Hirano, S. Yamamoto, Y. Akino, A. Nakamura, T. Yagi, H. Sugiura, T. Yanagisawa, Advanced solid-State photonics, OSA Technical Digest Series (CD) (Optical Society of America), (2009) WE1. Y. Hirano, T. Sasagawa, T. Yanagisawa, S. Yamamoto, A. Nakamura, T. Yagi, H. Sugiura, Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, OSA Technical Digest (CD) (Optical Society of America), 2009 PThA3. B. Yan, Y. Qi, Y. Wang, Proc. SPIE 10152 (2016) 1015217.
4
Contents lists available at ScienceDirect
Optik journal homepage: www.elsevier.com/locate/ijleo
Original research article
Compact CW Nd:YVO4/PPMgLN green laser Hong-Yi Lina,b,*, Xiao-Hua Huanga,b, Dong Suna,b, Lu-Ming Songa, Ji-Yan Zhanga,b a b
School of Optoelectronic and Communication Engineering, Xiamen University of Technology, Xiamen, 361024, China Fujian Key Laboratory of Optoelectronic Technology and Devices, Xiamen University of Technology, Xiamen, 361024, China
A R T IC LE I N F O
ABS TRA CT
Keywords: Green laser Nd:YVO4 laser PPMgLN
A compact and reliable linear-beam Nd:YVO4/PPMgLN green laser pumped by an edge-emitting laser diode array (24 separate emitters with an overall length of 480 μm and a gross power of 45 W at 807.1 nm) is achieved. The independent 24-edge-emitting array can achieve poor spatial coherence and effectively reduce laser speckle effect. In the air-cooled (water-cooled) condition, the maximum output power is 8.64 W (11.10 W), the optical-optical conversion efficiency is 24 % (25 %), and the power variation is less than 3 % (2 %) for 1 h (3 h).
1. Introduction The green lasers produced by frequency doubling technology have some advantages of stable performance, high efficiency and simple and compact structure. They are widely used in stage performance show, underwater communication, biomedical, laser display, 3D holographic display and other fields [1]. For the laser display, the main direction is to improve power and efficiency, reduce volume and power consumption, especially reduce coherence and eliminate laser speckle as far as possible. For 3D holographic display, the main direction is to reduce spectral line-width, enhance coherence (coherence length of several ten meters), optimize beam quality, improve power, reduce volume and realize direct high-speed modulation. Different requirements in the various fields have promoted the further development of the green lasers [2–4]. Here, we report a compact and reliable linear-beam Nd:YVO4/PPMgLN green laser pumped by an edge-emitting laser diode array and the maximum green power at 532.2 nm reaches 11.10 W. 2. Properties of the PPMgLN crystal KTP, LBO, LN, BBO and LT are the traditional non-linear crystals used for frequency doubling. In order to obtain high efficiency output, strict angular-phase-matching must be satisfied. The appearance of quasi-phase-matched periodically polarized crystals has greatly promoted the development of frequency doubling technology. Quasi-phase-matching makes full use of the maximum nonlinear coefficient of crystals, eliminates the walk-off effect and improves the conversion efficiency [5,6]. The commonly used periodically polarized crystals are PPLN, PPLT, PPKTP, PPMgLN, etc. Compared with PPLN and PPKTP, PPMgLN has a higher threshold of light damage resistance, and can achieve high efficiency at room temperature. The PPMgLT crystal has a small absorption coefficient, which is the best choice for several hundred watts green lasers. However, for low power green lasers, PPMgLN crystal is the best choice. The higher nonlinearity coefficient (16–22 pm/V) of PPMgLN reduces the requirement of fundamental laser power and improves the efficiency. Ref. [9] points out when the length of PPMgLN crystal is 2 mm, the temperature bandwidth and wavelength acceptance linewidth
⁎
Corresponding author at: School of Optoelectronic and Communication Engineering, Xiamen University of Technology, Xiamen, 361024, China. E-mail address: [email protected] (H.-Y. Lin).
https://doi.org/10.1016/j.ijleo.2019.163841 Received 9 September 2019; Accepted 20 November 2019 0030-4026/ © 2019 Elsevier GmbH. All rights reserved.
Please cite this article as: Hong-Yi Lin, et al., Optik - International Journal for Light and Electron Optics, https://doi.org/10.1016/j.ijleo.2019.163841
Optik - International Journal for Light and Electron Optics xxx (xxxx) xxxx
H.-Y. Lin, et al.
Fig. 1. Temperature acceptance bandwidth and wavelength acceptance linewidth versus the length of the PPMgLN crystal.
are 4.00 °C and 0.336 nm, respectively. However, when the length of PPMgLN crystal is 15 mm, the temperature bandwidth and wavelength acceptance linewidth reduce to 0.53 °C and 0.051 nm. Therefore, longer crystal has higher requirements on fundamental line-width, temperature control and mode matching. 3. Experimental setup There are two kinds of common frequency doubling structures: intra-cavity and single-pass external cavity. The output characteristics of the extra-cavity frequency doubling structure are more stable and reliable because the fundamental light and the nonlinear crystal are independent of each other. However, the fundamental light passes through PPMgLN crystal only once. In order to ensure the conversion efficiency, the length of PPMgLN crystal is generally longer (usually greater than 15 mm). On the other hand, the longer length of PPMgLN has, the lower the temperature bandwidth and fundamental linewidth of PPMgLN become (as shown in Fig. 1). Therefore, in order to take into account the conversion efficiency and compactness, most of the current frequency doubling technology has used the intracavity structure. The intracavity structure has the following advantages: 1) higher power of intracavity fundamental light reduces the requirement for the quality of fundamental beam; 2) compacter intracavity structure, easy to miniaturize, and even modular integration; 3) the intracavity structure reduces the requirement for PPMgLN length (usually 1−2 mm). Acceptance bandwidth is larger, which is easier to control temperature. In this paper, we use the intracavity structure in Fig. 2. The pump source (24 separate emitters with an overall length of 480 μm and a gross power of 45 W at 807.1 nm) and the Nd:YVO4 crystal (13 × 4 × 1.5 mm3 and 1.0 at. % Nd3+) are the same as the reference [2]. The input facet of the Nd:YVO4 crystal (Min) and the output coupler (Moc) are coated high-reflection (HR) at 1064.4 nm, the output facet of the Nd:YVO4 crystal is coated HR at 532.2 nm, and the both facets of the PPMgLN crystal and Moc are coated anti-reflection (AR) at 532.2 nm. The PPMgLN crystal (CTL Photonics) is 11 mm-wide, 1 mm-long and 1 mm-thick, and its polarization period is 6.95 μm. 4. Results In the air-cooled condition, the maximum output power is 8.64 W in Fig. 3, the optical-optical conversion efficiency is 24 %, and the power variation is less than 3 % for 1 h in Fig. 4. In order to improve the output power, thermal effect and power ability, a water-cooled radiator is used to control the Nd:YVO4
Fig. 2. The setup of the Nd:YVO4/PPMgLN laser. 2
Optik - International Journal for Light and Electron Optics xxx (xxxx) xxxx
H.-Y. Lin, et al.
Fig. 3. Output power in the air-cooled condition.
Fig. 4. Power stability for 1 h in the air-cooled condition.
and PPMgLN’s temperature. In the water-cooled condition, the maximum output power rises to 11.10 W at a pump power of 44.40 W in Fig. 5, the optical-optical conversion efficiency reaches 25 %, and the power variation is less than 2 % for 3 h. Table 1 lists output performances of multi-light-emitting arrayed LD-pumped green lasers at 532 nm [7–10]. We can see that, in contrast to other papers, the performance of our Nd:YVO4/PPMgLN green laser is very efficient and admirable. 5. Conclusion A compact and reliable linear-beam Nd:YVO4/PPMgLN green laser pumped by an edge-emitting laser diode array (24 separate emitters with an overall length of 480 μm and a gross power at 807.1 nm of 45 W) is achieved. In the water-cooled condition, the maximum output power is 11.10 W. The independent 24-edge-emitting array can efficiently reduce laser speckle effect and this green
Fig. 5. Output power in the water-cooled condition. 3
Optik - International Journal for Light and Electron Optics xxx (xxxx) xxxx
H.-Y. Lin, et al.
Table 1 Output performances of multi-light-emitting arrayed LD-pumped green lasers. (OO: optical-to-optical conversion efficiency; EO: electro-optical conversion efficiency). Research institute, Year
LD
PPMgLN
Output parameters
Mitsubishi Electric Corporation, Japan, 2008 [7]
15 arrayed LD
Mitsubishi Electric Corporation, Japan, 2009 [8]
15 arrayed LD
Planar-waveguide 4 mm Planar-waveguide
Mitsubishi Electric Corporation, Japan, 2009 [9]
15 arrayed LD
Chinese Academy of Sciences, 2016 [10] Here
19 arrayed LD 15 arrayed LD
Average power 7.6 W, Peak power 10.9 W, OO 40 %, EO 20 % CW 10.8 W, OO 40 %, EO 20 % Pulse, Peak power 11.4 W, Average power 3.8 W, OO 42 % CW 10.8 W, OO 40 %, EO 20 %, Temperature bandwidth 40 °C 3.12 W, OO 9.2 % CW air-cooled 8.64 W, OO 20 % CW water-cooled 11.10 W, OO 25 %
4 mm Planar-waveguide 4 mm 2 mm, 6.95 μm 1 mm, 6.95 μm
laser can be used in the laser display areas. Acknowledgments This paper is sponsored by the External Cooperation Program of Fujian Provincial Science and Technology Department (2018I0019), Scientific Research Fund of Fujian Provincial Education Department of China (JAT170409) and National Natural Science Foundation of China (11094304). References [1] [2] [3] [4] [5] [6] [7]
[8] [9] [10]
W.M. Yao, J. Gao, L. Zhang, J. Li, Y.B. Tian, Y.F. Ma, X.D. Wu, G.F. Ma, J.M. Yang, Y.B. Pan, X.J. Dai, Appl. Opt. 54 (2015) 5817–5821. H.-Y. Lin, M.-Y. Wu, J. Tang, D. Sun, Optik 192 (2019) 162951. J.-W. Xue, K. Li, Y.-J. Fang, H.-J. Xie, B.-H. Su, Laser J. 36 (2015) 20–23. O.B. Jensen, A.K. Hansen, A. Müller, B. Sumpf, P.M. Petersen, P.E. Andersen, Opt. Commun. 392 (2017) 167–170. J. Wei, H. Lu, P. Jin, K. Peng, Opt. Express 25 (2017) 3545–3552. T. Mochizuki, K. Kimura, Y. Maeda, K. Takahashi, N. Iwase, M. Oka, M. Saito, Advanced Solid-State Photonics, OSA Technical Digest Series (CD) (Optical Society of America, 2008), (2008) MG5. Y. Hirano, S. Yamamoto, Y. Koyata, M. Imaki, M. Okano, T. Hamaguchi, A. Nakamura, T. Yagi, T. Yanagisawa, Conference on Lasers and Electro-Optics/ Quantum Electronics and Laser Science Conference and Photonic Applications Systems Technologies, OSA Technical Digest (CD) (Optical Society of America), 2008 CPDA3. Y. Hirano, S. Yamamoto, Y. Akino, A. Nakamura, T. Yagi, H. Sugiura, T. Yanagisawa, Advanced solid-State photonics, OSA Technical Digest Series (CD) (Optical Society of America), (2009) WE1. Y. Hirano, T. Sasagawa, T. Yanagisawa, S. Yamamoto, A. Nakamura, T. Yagi, H. Sugiura, Conference on Lasers and Electro-Optics/International Quantum Electronics Conference, OSA Technical Digest (CD) (Optical Society of America), 2009 PThA3. B. Yan, Y. Qi, Y. Wang, Proc. SPIE 10152 (2016) 1015217.
4