飞秒激光直写光纤光栅在光纤激光器中的应用研究
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摘要
伴随着高功率半导体激光器和新型包层泵浦技术的发展,近红外波段的高功率光纤激光器成为了人们研究的热点课题。光纤激光器的高斜效率、宽的波长调节范围以及在高功率条件下近衍射极限的光束质量等优点,使其在军事、通信、医疗等方面具有广泛的应用。
光纤激光器可以分为两类:一类是利用二向色镜及体光栅等作为波长选择元件的光纤激光器。这类系统具有较大的灵活性,但结构复杂、造价高。另一类是采用光纤布拉格光栅(FBG)作为选频元件的光纤激光器。FBG具有很好的选频作用,能够实现窄带激光输出,并且易于光纤集成、结构简单紧凑。近年来,利用飞秒光源,采用逐点刻写方法在各种光纤内制作布拉格光栅用于光纤激光器和光纤传感等领域的研究成为热点,此方法不需要光敏光纤,操作简单,光栅周期可以灵活选取,并且刻写的光栅具有很高的热稳定性。本论文采用相干公司的飞秒光源在Hi1060光纤内直写光纤布拉格光栅作为光纤激光器输出镜和波长选择元件,实现了基于光纤光栅的全光纤化光纤激光器。本文的主要研究工作如下:
1、概述了光纤激光器的优点以及近年来国内外采用飞秒激光制作FBG并将其应用在光纤激光器的研究进展。
2、详细介绍了光纤布拉格光栅的耦合模理论,计算了光纤布拉格光栅的反射谱,并讨论了谐振波长、光谱带宽等参量随写入条件的变化规律。
3、讨论了飞秒激光与石英材料作用的物理机制,并对飞秒直写光纤布拉格光栅的曝光点形状及折射率调制进行了分析。
4、运用速率方程理论,对光纤激光器的输出特性、增益和阈值特性等进行了理论分析,运用Matlab软件对光纤的最佳长度、输出耦合镜的最佳反射率等进行了数值模拟。并研究了不同参量对激光器输出性能的影响。
5、运用800nm的飞秒激光进行了刻写光纤布拉格光栅的实验,实验中得到了周期为2.9 ? m的8mm光纤光栅,这是相应于中心波长在1042nm的八阶光纤光栅。并以其做为光纤激光器输出镜实现了激光输出。
High power near infrared fiber lasers have become a topic of great interest, attribute to the development of high power laser diodes (LD) and optimization design of optical fiber. High slope efficiencies, power scalability, broad wavelength tunability, and diffraction-limited beam quality at high power make fiber lasers useful for a range of applications, such as military, telecommunication, medical and so on.
Fiber lasers fall into two main categories: the first one is those use wavelength selective elements, such as dichroic mirrors and bulk gratings, external to the laser fiber. These systems offer the greatest flexibility, but have a complicated structure and high-cost. The other type is those use fiber Bragg gratings (FBG) as wavelength selective elements. FBG plays an important role in frequency selection, so we can realize a very narrow band wavelength output when it is applied to the fiber lasers. Besides, this type of fiber lasers is more compact and easy to be integrated.
Recently, FBGs inscribed in several types of fiber point-by-point with a focused femtosecond laser pulses and its application in fiber lasers and sensors attracted a lot of researcher’s interests. This technique possesses many advantages, such as the needless of photosensitive fibers, simple operation system, flexible selection of the grating period, as well as the good thermal stability of the FBGs. In this article, we obtained a FBG inscribed directly into the core of Corning Hi-1060 fiber with a femtosecond laser made by Co. Coherence, and the FBG was applied in fiber laser as output coupler and wavelength selective element. We realized a FBG based, all fiber double clad fiber laser. The main works of this article are as follows:
1、The advantages of the fiber laser and the recent development of FBG fabricated with femtosecond laser for the application in fiber lasers were summarized.
2、The couple mode theory of fiber Bragg gratings was analyzed in detail. The reflective spectrum was calculated. The variation of the resonation wavelength as well as the bandwidth with the change of writing condition was discussed.
3、Physical mechanism of the femtosecond laser interactions with quartz material was analyzed, then the spot shape and the refractive index modulation profile of the femtosecond laser induced FBGs were studied.
4、On the basis of rate equation theory, gain、threshold and output characteristics of the fiber laser were analyzed. Optimum fiber length and reflectivity of the output mirror were simulated with the MATLAB software. And then the influence of different parameters on laser characteristics was discussed.
5、FBG of 8mm length with a period of 2.9 ? m was inscribed into the Hi1060 fiber by a 800nm femtosecond laser. This is the eight-order grating at 1042nm. As the output mirror, this FBG was applied in the fiber laser and we realized laser output.
光纤激光器可以分为两类:一类是利用二向色镜及体光栅等作为波长选择元件的光纤激光器。这类系统具有较大的灵活性,但结构复杂、造价高。另一类是采用光纤布拉格光栅(FBG)作为选频元件的光纤激光器。FBG具有很好的选频作用,能够实现窄带激光输出,并且易于光纤集成、结构简单紧凑。近年来,利用飞秒光源,采用逐点刻写方法在各种光纤内制作布拉格光栅用于光纤激光器和光纤传感等领域的研究成为热点,此方法不需要光敏光纤,操作简单,光栅周期可以灵活选取,并且刻写的光栅具有很高的热稳定性。本论文采用相干公司的飞秒光源在Hi1060光纤内直写光纤布拉格光栅作为光纤激光器输出镜和波长选择元件,实现了基于光纤光栅的全光纤化光纤激光器。本文的主要研究工作如下:
1、概述了光纤激光器的优点以及近年来国内外采用飞秒激光制作FBG并将其应用在光纤激光器的研究进展。
2、详细介绍了光纤布拉格光栅的耦合模理论,计算了光纤布拉格光栅的反射谱,并讨论了谐振波长、光谱带宽等参量随写入条件的变化规律。
3、讨论了飞秒激光与石英材料作用的物理机制,并对飞秒直写光纤布拉格光栅的曝光点形状及折射率调制进行了分析。
4、运用速率方程理论,对光纤激光器的输出特性、增益和阈值特性等进行了理论分析,运用Matlab软件对光纤的最佳长度、输出耦合镜的最佳反射率等进行了数值模拟。并研究了不同参量对激光器输出性能的影响。
5、运用800nm的飞秒激光进行了刻写光纤布拉格光栅的实验,实验中得到了周期为2.9 ? m的8mm光纤光栅,这是相应于中心波长在1042nm的八阶光纤光栅。并以其做为光纤激光器输出镜实现了激光输出。
High power near infrared fiber lasers have become a topic of great interest, attribute to the development of high power laser diodes (LD) and optimization design of optical fiber. High slope efficiencies, power scalability, broad wavelength tunability, and diffraction-limited beam quality at high power make fiber lasers useful for a range of applications, such as military, telecommunication, medical and so on.
Fiber lasers fall into two main categories: the first one is those use wavelength selective elements, such as dichroic mirrors and bulk gratings, external to the laser fiber. These systems offer the greatest flexibility, but have a complicated structure and high-cost. The other type is those use fiber Bragg gratings (FBG) as wavelength selective elements. FBG plays an important role in frequency selection, so we can realize a very narrow band wavelength output when it is applied to the fiber lasers. Besides, this type of fiber lasers is more compact and easy to be integrated.
Recently, FBGs inscribed in several types of fiber point-by-point with a focused femtosecond laser pulses and its application in fiber lasers and sensors attracted a lot of researcher’s interests. This technique possesses many advantages, such as the needless of photosensitive fibers, simple operation system, flexible selection of the grating period, as well as the good thermal stability of the FBGs. In this article, we obtained a FBG inscribed directly into the core of Corning Hi-1060 fiber with a femtosecond laser made by Co. Coherence, and the FBG was applied in fiber laser as output coupler and wavelength selective element. We realized a FBG based, all fiber double clad fiber laser. The main works of this article are as follows:
1、The advantages of the fiber laser and the recent development of FBG fabricated with femtosecond laser for the application in fiber lasers were summarized.
2、The couple mode theory of fiber Bragg gratings was analyzed in detail. The reflective spectrum was calculated. The variation of the resonation wavelength as well as the bandwidth with the change of writing condition was discussed.
3、Physical mechanism of the femtosecond laser interactions with quartz material was analyzed, then the spot shape and the refractive index modulation profile of the femtosecond laser induced FBGs were studied.
4、On the basis of rate equation theory, gain、threshold and output characteristics of the fiber laser were analyzed. Optimum fiber length and reflectivity of the output mirror were simulated with the MATLAB software. And then the influence of different parameters on laser characteristics was discussed.
5、FBG of 8mm length with a period of 2.9 ? m was inscribed into the Hi1060 fiber by a 800nm femtosecond laser. This is the eight-order grating at 1042nm. As the output mirror, this FBG was applied in the fiber laser and we realized laser output.
引文
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2 E. Snitzer, H. Po, F. Hakimi,et al. Double-clad, offset core Nd fiber laser, Proceedings of Optical Fiber Sensors '88, New Orleans, Postdealine paper PD 5, 1988.
3 N. Jovanovic, A. Fuerbach, et al. Stable high-power continuous-wave Yb3+-doped silica fiber laser utilizing a point-by-point inscribed fiber Bragg grating. Opt. Lett. 2007,32(11):1486-1488
4 N. Jovanovic, et al. Narrow linewidth, 100 W cw Yb3+-doped silica fiber laser with a point-by-point Bragg grating inscribed directly into the active core [J]. Optics Letters, 2007, 32(19): 2804-2806.
5江超,王东宁.飞秒激光脉冲刻写光纤布拉格光栅的研究进展[J].激光与光电子学进展, 2008,45(6):59-66
6 A.S. Kurkov, V.I. Karpov, A.Y. Laptev, et al. Highly efficient cladding-pumped fiber laser based on an ytterbium-doped optical fiber and a fiber Bragg grating [J]. Quantum Electronics,1999,29(6):516-517
7 A.S. Kurkov, A.Y. Laptev, E.M. Dianov, et al. Yb3+-doped double-clad fibers and lasers [J]. Proceedings of SPIE, 2000,4083:118-126
8 A.S. Kurkov, Grukh D.A., Medurdkovol, et al. Multimode fiber lasers based on Bragg gratings and double-clad Yb-doped fibers [J]. Laser Phys. Lett., 2004, 1(9):473-475
9 Y.P. Wang, et al. Fiber Bragg grating inscription in pure-silica and Ge-doped photonic crystal fibers [J]. Applied Optics, 2009, 48(11): 1963-1968.
10 M. Becker, et al. Fiber Bragg grating inscription with DUV femtosecond exposure and two beam interference [J]. Proc. SPIE, 2009,7386:73862Y
11 E. Lindner, C. Chojetzki, et al. Thermal regeneration of fiber Bragg gratings in photosensitive fibers [J]. Optcs Express,2009,17(15):12523-12531
12 S.J. Mihailov, et al. Bragg gratings written in all-SiO2 and Ge-doped core fibers with 800nm femtosecond radiation and a phase mask [J]. IEEE J. Lightwave Techology, 2004,22(1): 94-100
13 S.J. Mihailov, et al.. Through-the-jacket inscription of fiber Bragg gratings using femtosecond infrared radiation for sensor applications[J]. Proc. SPIE, 2009,7316:73160B
14 M. Bernier, R. Vallee, et al. Ytterbium fiber laser based on first-order fiber Bragg gratings written with 400nm femtosecond pulses and a phase mask[J]. Optics Express,2009,17(21):18887-18893
15 P. Kelleher, D.N. Nikogosyan. Inscription of narrow-band fiber Bragg gratings with 264nm femtosecond pulses [J]. Optical Fiber Technology,2010
16 S. Back, Soh.D.B.S, Jeong Y., et al.. A cladding-pumped fiber laser with pump- reflecting inner-cladding Bragg grating [J]. IEEE Photo.Technol.Lett., 2004, 16(2):407-409
17 Wikszak E., Burghoff J., Will M, et al. Recording of fiber Bragg gratings with femtosecond pulses using a“point-by-point”technique [A].CLEO,2004,2:2
18 A.Martinez, M.Dubov, I.Khrushchev, I.Bennion. Direct writing of fiber Bragg gratings by femtosecond laser[J].Electron.Lett.,2004,40(19):1170-1171
19 A.Martinez, I.Y.Khrushchev, I.Bennion. Thermal properties of fiber Bragg gratings inscribed point- by- point by infrared femtosecond laser[J]. Electron. Lett., 2005, 41(4):176-177
20 A.Martinez, I.Y.Khrushchev, I.Bennion. Direct inscription of Bragg gratings in coated fibers by an infrared femtosecond laser[J]. Opt.Lett., 2006,31(11):1603- 1605
21 Y.Lai, A.Martinez, I.Khrushchev, et al.. Distributed Bragg reflector fiber laser fabricated by femtosecond laser inscription[J].Opt.Lett.,2006,31(11):1672-1674
22 K. Kalli, T. Geernaert, et al. Point-by-point Bragg grating inscription in single-mode microstructure fiber using NIR femtosecond laser. Proc.SPIE,2009, 7503:75037O1-75037O4
23 N.Jovanovic, G.D.Marshall, A.Fuerbach, G.Town, and M.J.Withford. Compact, all fiber, linearlypolarised, single-mode Ytterbium doped fiber laser utilizing point-by-point inscribed intra-core fiber Bragg gratings. Proc. SPIE 6801,68010O (2008)
24 T. Geernaert, K. Kalli, et al. Point-by-point fiber Bragg grating inscription in free-standing step-index and photonic crystal fibers using near-IR femtosecond laser[J]. Opt. Lett.,2010,35(10):1647-1649
25 Y. Lai, K. Zhou, et al. Point-by-point inscription of first-order fiber Bragg grating for C-band application[J]. Optics Express,2007,15(26):18318-18325
26 R.J. Williams, N. Jovanovic, et al. All-optical, actively Q-switched fiber laser [J]. Optics Express,2010,18(8):7714-7723
27 M.K. Davis, M.J.F. Davis, et al. Thermal effects in doped fibers [J]. J. Lightwave Technol.,1998,16(6)1013-1023
28胡贵军,潘玉寨,郭玉彬,张亮张军,王立军.基于光纤光栅的高功率光纤激光器[J].光子学报,2004,33(4),405
29潘玉寨,张军,胡贵军,张亮,刘云,王立军.利用光纤光栅的高功率掺镱光纤激光器[J].光学学报,2004,24(9),1237
30李丽君,范万德,付圣贵等.双包层光纤光栅选频双包层光纤激光器[J].光学学报,2005, 25(1),55
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33 C.W. Song, Y.J. Zhang, B.Q. Yao, Y. Wang, W. Wang, Y.L. Ju, Y.Z. Wang. Double-clad Tm3+-doped silica fiber laser with Bragg grating inscribed directly into active core by femtosecond laser [J]. Laser Physics, 2009, 19(5): 1009
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48 N. Jovanovic, J. Thomas, et al. Polarization-dependent effects in point-by-point fiber Bragg gratings enable simple, linearly polarized fiber lasers [J]. Optics Express,2009,17(8):6082-6095
49 A. Martinez. et al., Photoinduced modification in fiber gratings inscribed directly by infrared femtosecond irradiation [J]. IEEE Photonics Techn. Lett., 2006,18(21):2266-2268
50 J.L. Liu, C.J. Zhao, et al. The optimum length of linear cavity Yb3+-doped double-clad fiber laser [J]. Opt. Commun.,2010,283:1449-1553
51张亮.全光纤型包层泵浦掺镱离子光纤激光器的研究[D].中国科学院博士学位论文.2005
2 E. Snitzer, H. Po, F. Hakimi,et al. Double-clad, offset core Nd fiber laser, Proceedings of Optical Fiber Sensors '88, New Orleans, Postdealine paper PD 5, 1988.
3 N. Jovanovic, A. Fuerbach, et al. Stable high-power continuous-wave Yb3+-doped silica fiber laser utilizing a point-by-point inscribed fiber Bragg grating. Opt. Lett. 2007,32(11):1486-1488
4 N. Jovanovic, et al. Narrow linewidth, 100 W cw Yb3+-doped silica fiber laser with a point-by-point Bragg grating inscribed directly into the active core [J]. Optics Letters, 2007, 32(19): 2804-2806.
5江超,王东宁.飞秒激光脉冲刻写光纤布拉格光栅的研究进展[J].激光与光电子学进展, 2008,45(6):59-66
6 A.S. Kurkov, V.I. Karpov, A.Y. Laptev, et al. Highly efficient cladding-pumped fiber laser based on an ytterbium-doped optical fiber and a fiber Bragg grating [J]. Quantum Electronics,1999,29(6):516-517
7 A.S. Kurkov, A.Y. Laptev, E.M. Dianov, et al. Yb3+-doped double-clad fibers and lasers [J]. Proceedings of SPIE, 2000,4083:118-126
8 A.S. Kurkov, Grukh D.A., Medurdkovol, et al. Multimode fiber lasers based on Bragg gratings and double-clad Yb-doped fibers [J]. Laser Phys. Lett., 2004, 1(9):473-475
9 Y.P. Wang, et al. Fiber Bragg grating inscription in pure-silica and Ge-doped photonic crystal fibers [J]. Applied Optics, 2009, 48(11): 1963-1968.
10 M. Becker, et al. Fiber Bragg grating inscription with DUV femtosecond exposure and two beam interference [J]. Proc. SPIE, 2009,7386:73862Y
11 E. Lindner, C. Chojetzki, et al. Thermal regeneration of fiber Bragg gratings in photosensitive fibers [J]. Optcs Express,2009,17(15):12523-12531
12 S.J. Mihailov, et al. Bragg gratings written in all-SiO2 and Ge-doped core fibers with 800nm femtosecond radiation and a phase mask [J]. IEEE J. Lightwave Techology, 2004,22(1): 94-100
13 S.J. Mihailov, et al.. Through-the-jacket inscription of fiber Bragg gratings using femtosecond infrared radiation for sensor applications[J]. Proc. SPIE, 2009,7316:73160B
14 M. Bernier, R. Vallee, et al. Ytterbium fiber laser based on first-order fiber Bragg gratings written with 400nm femtosecond pulses and a phase mask[J]. Optics Express,2009,17(21):18887-18893
15 P. Kelleher, D.N. Nikogosyan. Inscription of narrow-band fiber Bragg gratings with 264nm femtosecond pulses [J]. Optical Fiber Technology,2010
16 S. Back, Soh.D.B.S, Jeong Y., et al.. A cladding-pumped fiber laser with pump- reflecting inner-cladding Bragg grating [J]. IEEE Photo.Technol.Lett., 2004, 16(2):407-409
17 Wikszak E., Burghoff J., Will M, et al. Recording of fiber Bragg gratings with femtosecond pulses using a“point-by-point”technique [A].CLEO,2004,2:2
18 A.Martinez, M.Dubov, I.Khrushchev, I.Bennion. Direct writing of fiber Bragg gratings by femtosecond laser[J].Electron.Lett.,2004,40(19):1170-1171
19 A.Martinez, I.Y.Khrushchev, I.Bennion. Thermal properties of fiber Bragg gratings inscribed point- by- point by infrared femtosecond laser[J]. Electron. Lett., 2005, 41(4):176-177
20 A.Martinez, I.Y.Khrushchev, I.Bennion. Direct inscription of Bragg gratings in coated fibers by an infrared femtosecond laser[J]. Opt.Lett., 2006,31(11):1603- 1605
21 Y.Lai, A.Martinez, I.Khrushchev, et al.. Distributed Bragg reflector fiber laser fabricated by femtosecond laser inscription[J].Opt.Lett.,2006,31(11):1672-1674
22 K. Kalli, T. Geernaert, et al. Point-by-point Bragg grating inscription in single-mode microstructure fiber using NIR femtosecond laser. Proc.SPIE,2009, 7503:75037O1-75037O4
23 N.Jovanovic, G.D.Marshall, A.Fuerbach, G.Town, and M.J.Withford. Compact, all fiber, linearlypolarised, single-mode Ytterbium doped fiber laser utilizing point-by-point inscribed intra-core fiber Bragg gratings. Proc. SPIE 6801,68010O (2008)
24 T. Geernaert, K. Kalli, et al. Point-by-point fiber Bragg grating inscription in free-standing step-index and photonic crystal fibers using near-IR femtosecond laser[J]. Opt. Lett.,2010,35(10):1647-1649
25 Y. Lai, K. Zhou, et al. Point-by-point inscription of first-order fiber Bragg grating for C-band application[J]. Optics Express,2007,15(26):18318-18325
26 R.J. Williams, N. Jovanovic, et al. All-optical, actively Q-switched fiber laser [J]. Optics Express,2010,18(8):7714-7723
27 M.K. Davis, M.J.F. Davis, et al. Thermal effects in doped fibers [J]. J. Lightwave Technol.,1998,16(6)1013-1023
28胡贵军,潘玉寨,郭玉彬,张亮张军,王立军.基于光纤光栅的高功率光纤激光器[J].光子学报,2004,33(4),405
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