基于飞秒激光刻写光纤光栅的研究进展

李宏业; 饶斌裕; 赵晓帆; 胡琪浩; 王蒙; 王泽锋

doi:doi:10.3788/LOP57.111420

激光与光电子学进展, 2020, 57 (11): 111420, 网络出版: 2020-06-02

基于飞秒激光刻写光纤光栅的研究进展下载： 2665次

Development of Fiber Gratings Inscribed by Femtosecond Laser

李宏业 ¹饶斌裕 ¹赵晓帆 ¹胡琪浩 ¹王蒙 ^1,2,3王泽锋 ^1,2,3,*

作者单位

¹ 国防科技大学前沿交叉学科学院, 湖南长沙 410073

² 脉冲功率激光技术国家重点实验室, 湖南长沙 410073

³ 高能激光技术湖南省重点实验室, 湖南长沙 410073

图 & 表

图 1. 逐点刻写的包层模耦合情况^[18]

Fig. 1. Transmission spectrum of a point-by-point inscribed FBG^[18]

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图 2. 采用逐点刻写的方法制备FBG。 (a)实验装置;(b)刻写在不同位置的不同周期光栅的显微图与光谱;(c)刻写在不同位置相同周期光栅的光谱^[21]

Fig. 2. FBG preparation by point-by-point writing. (a)Experimental device; (b) microscope images and reflection spectra of FBGs with different periods written in different positions; (c) spectrum of FBGs with the same period written in different positions^[21]

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图 3. 在扭转的七芯光纤上刻写FBG阵列^[23]

Fig. 3. FBG array inscription in twist seven-core fiber^[23]

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图 4. 采用逐线刻写的方法制备FBG。 (a)飞秒激光逐线刻写示意图;(b)四阶FBG显微示意图;(c)逐线刻写FBG透射谱^[24]

Fig. 4. FBG preparation by line-by-line writing. (a) Schematic of femtosecond laser line-by-line inscription; (b) microscopic of fourth-order FBG; (c) transmission spectrum of line-by-line inscribed FBG^[24]

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图 5. π相移光栅。(a)光栅在不同偏振态下的透射谱;(b)不同扭转角下,P₁-P₂的变化曲线^[26]

Fig. 5. π phase shift grating. (a) Transmission spectrum of different polarization states; (b) curves of P₁-P₂ with different twist angles^[26]

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图 6. 逐线刻写光栅阵列。(a) FBG阵列编码的3位二进制编码的示意图;(b)编码111的FBG阵列的后向散射^[28]

Fig. 6. Line-by-line writing grating array. (a) Schematic diagram of the encoded FBG array with a 3-bit binary coding; (b) backscattering of FBG array with code 111^[28]

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图 7. 逐面刻写光栅阵列。(a) FBG阵列^[29];(b)倾斜角为7°的TFBG光谱^[30]

Fig. 7. Plane-by-plane writing grating array. (a) FBGs array^[29]; (b) TFBG spectrum with a tilt angle of 7°^[30]

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图 8. 铒镱共掺的双包层光纤上刻写光栅对。(a)光栅光谱图;(b)振荡器光路;(c)斜率效率^[33]

Fig. 8. Grating pair on double-clad fiber co-doped with Er and Yb. (a) Spectrum of FBGs; (b) schematic of oscillator; (c) slope efficiency^[33]

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图 9. 实验结果。(a) 45°倾斜光栅插损与偏振相关损耗;(b)非线性偏振旋转锁模光路;(c)单孤子锁模光谱;(d)单孤子锁模自相关;(e)类噪声锁模光谱;(f)类噪声锁模自相关^[34]

Fig. 9. Experimental results. (a) Polarization dependent loss and insertion loss of 45° tilt grating; (b) schematic of NPR mode-locked fiber laser; (c) optical spectrum of single-soliton mode-locked fiber laser; (d) autocorrelation of single-soliton mode-locked fiber laser; (e) optical spectrum of noise-like mode-locked fiber laser; (f) autocorrelation of noise-like mode-locked fiber laser^[34]

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图 10. 实验结果。(a)逐面刻写光栅的光路;(b) type I型FBG光谱;(c)改变重复频率实现type I型CFBG刻写; (d) type II型FBG光谱^[35]

Fig. 10. Experimental results. (a) Schematic of plane-by-plane inscription; (b) spectrum of type I FBG; (c) spectrum of type I CFBG; (d) spectrum of type II FBG^[35]

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图 11. 纤芯扫描技术。(a)示意图;(c)纤芯扫描与逐点刻写的FBG光谱对比^[36]

Fig. 11. Core-scanning technology. (a) Schematic of core-scanning; (b) FBG spectrum comparison of core-scanning and point-by-point ^[36]

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图 12. 不同方法刻写的CFBG。(a)逐点刻写;(b)纤芯扫描;(c)改进型纤芯扫描;(d)逐点刻写CFBG的光谱;(e)纤芯扫描刻写CFBG的光谱;(f)改进纤芯扫描刻写CFBG的光谱^[37]

Fig. 12. CFBG written by different methods. (a) Point-by-point; (b) core-scanning; (c) modified core-scanning spectrum of CFBG by point-by-point; (d) spectrum of CFBG by core-scanning; (e) spectrum of CFBG by modified core-scanning^[37]

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图 13. 双芯少模光栅。(a)实验光路;(b)局部放大图^[41]

Fig. 13. Twin-core FMFBG. (a) Experimental optical path; (b) partial enlarged view^[41]

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图 14. TMFBG。(a)刻写TMFBG示意图;(b)TMFBG光谱图^[45]

Fig. 14. TMFBG. (a) Schematic of TMFBG inscription; (b) spectrum of TMFBG^[45]

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图 15. 实验结果。(a)保留涂敷层(蓝)与去除涂敷层(黑)的光谱;(b)斜率效率与实验光路^[47]

Fig. 15. Experimental results. (a) Spectrum of FBG (blue is with coating, black is without coating);(b) slope efficiency and schematic of oscillator^[47]

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图 16. 在未去涂敷层的光纤上刻写FBG。(a)刻写光栅光路;(b)重复频率为1 kHz,曝光时间为5 min的光谱;(c)重复频率为500 Hz,曝光时间为10 min的光谱^[49]

Fig. 16. Writing FBG on the optical fiber without decoating. (a) Schematic of FBG inscription; (b) spectrum of FBG with repetition rate 1 kHz and exposure time 5 min; (c) spectrum of FBG with repetition rate 500 Hz and exposure time 10 min^[49]

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图 17. 飞秒激光相位模板扫描技术。(a)相位模板扫描刻写示意图;(b)光栅透射谱以及透射深度随光栅长度的变化^[50]

Fig. 17. Femtosecond laser phase template scanning technology. (a) Schematic of phase mask scanning technology; (b) transmission spectra and transmission over length^[50]

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图 18. 相位模板扫描技术。(a)掺铒光纤刻写FBG透射谱;(b)激光器示意图;(c)斜率效率^[51]

Fig. 18. Phase mask scanning technology. (a) Transmission spectrum of FBG in EDF; (b) laser experiment setup; (c) slope efficiency^[51]

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图 19. 实验结果。(a) CFBG光谱;(b)激光器光路;(c)高功率激光器斜率效率^[53]

Fig. 19. Experimental results. (a) Spectrum of CFBG; (b) laser experiment setup; (c) slope efficiency^[53]

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图 20. 实验结果。(a)内包层CFBG光谱;(b)激光器光路^[54]

Fig. 20. Experimental results. (a) Spectrum of inner-cladding CFBG; (b) laser experiment setup^[54]

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表 1不同飞秒激光直写方式的对比

Table1. Comparison of various femtosecond laser direct inscribing methods

Method	Point-by-point	Line-by-line	Plane-by-plane	Core-scanning
Alignment	Extremely high	High	Low	High
Pulse energy /(nJ/pulse)	50—500	100	100	100
Insertion loss	High IL at shorterwavelength	High IL at shorterwavelength	Low IL	Low IL
Application	Sensors(especially hightemperature sensors)	Sensing by birefringencecharacteristics	Sensors andlasers	Sensors

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表 2相位模板刻写技术的对比

Table2. Comparison between phase mask writing methods

Method	Static inscription	Dynamic inscription
Stability requirements	Low	High
System complexity	Low	High
Inscription time	Short	Long
Grating length	Limited by beam diameter	Limited by phase mask
Application	Sensors	High power fiber laser

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表 3国内外飞秒激光刻写光纤光栅的进展情况

Table3. Development of fiber gratings inscribed by using femtosecond laser

Reference	λ_fs /nm	f /kHz	T /fs	E /nJ	Description	P /μm	λ_R /nm
[15]	800	200	120		First reported PBPLPG	DW	1100-1700
[16]	800	1	150	300-1000	First reported PBP FBG	DW	1550
[17]	800	1	120	160-300	Loss mechanism of PBP	DW	1550
[18]	800		110	200-275	Cladding mode coupling	DW	1540
[19]	800			80-350	Impact of scattering loss on FBG reflectivity	DW	1550
[20]	800	1	100	200	Sampling FBG with hightemperature resistance	DW	1550
[21]	800	1	100	200	Parallel-integrated FBGs	DW	1550
[22]	800	1	100	59-174	Mie scattering suppression in PBP FBG	DW	1550
[23]	1030	1	232	200	Bending sensing by seven cores FBG	DW	1550
[24]	800	1	110	85	LBL inscribed low IL and PDL FBG	DW	1600
[25]	266	1	120	4×10⁶(maxima)	High birefringence FBGby LBL inscription	DW	1550
	520	200	400		LBL polarization-dependentπ-PSFBG for twist sensing	DW	1550
[27]				130	π-PSFBG for strain sensing	DW	1550
[28]	513	200	250	14	LBL inscribed fiber label	DW	1550
[29]		4		100	FBGs array for vibration sensor	DW	1550
[30]	517	50	220	100	High order resonance of TFBG	DW	1560
[31]	517	5	220	80	Polymer fiber grating sensor	DW	1550
[32]	517		220		Polymer fiber grating sensor	DW	1550
[33]	517	100	220	150	FBGs in oscillator	DW	1560
[34]	517	50	217	150	NPR mode locked by 45° TFBG	DW	1560
[35]	800	0.25	120	1400-1900	Beam expanding Pl-B-Pl	DW	1550
[36]	800	1	120	117	Core-scanning Low loss FBG	DW	1540
[37]	800	0.1-1	112	83-200	Core-scanning CFBG	DW	1540
[38]	800	0.01、1	120	3×10⁵	First report of femtosecond laser andphase mask inscribed FBG	4.284, 3.213,2.142, 1.071	1550
[39]	800	0.125	125	6×10⁵	Cladding mode suppression byfocal point scanning	3.213	1550
[40]	800	1	100	1.08×10⁵-2.67×10⁵	Negative refractiveindex FBG	1.070	1550
[41]	800	1	100	1.02×10⁵	Double cores FBG	1.070	1550
[42]	800	1	100	2×10⁵	PCFBG for refractiveindex sensing	1.070	1550
[43]	800	0.1		0.4×10⁶-0.5×10⁶	Higher order resonance	1.071	600-1700
[44]	800	1	50	4.2×10⁵	Cladding mode resonancein two mode fiber	2.142	1550
[45]	800	1	35	4×10⁶(maxima)	Cladding mode resonancein two mode fiber	2.142	1550
[46]	1030	0.1	190		PCFBG	2.175	1560
[47]	266	1	40		Oscillator used FBG inscriptionwithout coating removing	1.0742	1550
[48]	800	1	80	0.78×10⁶;1.1×10⁶	Strong cladding mode resonantFBG by beam expanding	1.07	1300-1550
[49]	800	0.2-1	35	0.4×10⁶	focal point scanning FBGwithout coating removing	2.14	1550
[50]	800	1	50	2×10⁵,6×10⁵	phase mask scanning FBG	2.15	1555
[51]	800	1	50	6×10⁵	High reflection FBG onEDF for oscillator	2.15	1555
[52]	800		120		Oscillator with514 W output		1078.7
[53]	800		100		Oscillator with1.9 kW output		1070
[54]	403	1	30	6×10⁶	Pump reflector	0.674	976

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表 4飞秒激光直写与相位模板辅助刻写技术的对比

Table4. Comparison between direct inscribing and phase mask assisted writing

Method	Direct writing	Phase mask assisted writing
Pulse energy /(nJ/pulse)	100	0.5
Resonance wavelength	Arbitrary	Limited by phase mask
IL	High	Low
Flexibility	High	Low
Alignment	High	Low
Repeatability	Low	High
Characteristics of gratings	1. High polarization-related properties and high birefringence properties2. Easily fabrication of novel gratings by adjusting inscription condition	Stable spectral properties
Application	Novel sensors and quasi-distributed sensors	Sensors and lasers
Developing trend	1. Inscription of FBGs array with different resonance wavelengths to realize quasi-distributed sensors2. Inscription fiber gratings with special refractive index profile to control mode coupling	Inscription of fiber gratingsin high power oscillator

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李宏业, 饶斌裕, 赵晓帆, 胡琪浩, 王蒙, 王泽锋. 基于飞秒激光刻写光纤光栅的研究进展[J]. 激光与光电子学进展, 2020, 57(11): 111420. Hongye Li, Binyu Rao, Xiaofan Zhao, Qihao Hu, Meng Wang, Zefeng Wang. Development of Fiber Gratings Inscribed by Femtosecond Laser[J]. Laser & Optoelectronics Progress, 2020, 57(11): 111420.

基于飞秒激光刻写光纤光栅的研究进展 下载： 2665次

图 1. 逐点刻写的包层模耦合情况[18]

Fig. 1. Transmission spectrum of a point-by-point inscribed FBG[18]

图 2. 采用逐点刻写的方法制备FBG。 (a)实验装置;(b)刻写在不同位置的不同周期光栅的显微图与光谱;(c)刻写在不同位置相同周期光栅的光谱[21]

Fig. 2. FBG preparation by point-by-point writing. (a)Experimental device; (b) microscope images and reflection spectra of FBGs with different periods written in different positions; (c) spectrum of FBGs with the same period written in different positions[21]

图 3. 在扭转的七芯光纤上刻写FBG阵列[23]

Fig. 3. FBG array inscription in twist seven-core fiber[23]

图 4. 采用逐线刻写的方法制备FBG。 (a)飞秒激光逐线刻写示意图;(b)四阶FBG显微示意图;(c)逐线刻写FBG透射谱[24]

Fig. 4. FBG preparation by line-by-line writing. (a) Schematic of femtosecond laser line-by-line inscription; (b) microscopic of fourth-order FBG; (c) transmission spectrum of line-by-line inscribed FBG[24]

图 5. π相移光栅。(a)光栅在不同偏振态下的透射谱;(b)不同扭转角下,P1-P2的变化曲线[26]

Fig. 5. π phase shift grating. (a) Transmission spectrum of different polarization states; (b) curves of P1-P2 with different twist angles[26]

图 6. 逐线刻写光栅阵列。(a) FBG阵列编码的3位二进制编码的示意图;(b)编码111的FBG阵列的后向散射[28]

Fig. 6. Line-by-line writing grating array. (a) Schematic diagram of the encoded FBG array with a 3-bit binary coding; (b) backscattering of FBG array with code 111[28]

图 7. 逐面刻写光栅阵列。(a) FBG阵列[29];(b)倾斜角为7°的TFBG光谱[30]

Fig. 7. Plane-by-plane writing grating array. (a) FBGs array[29]; (b) TFBG spectrum with a tilt angle of 7°[30]

图 8. 铒镱共掺的双包层光纤上刻写光栅对。(a)光栅光谱图;(b)振荡器光路;(c)斜率效率[33]

Fig. 8. Grating pair on double-clad fiber co-doped with Er and Yb. (a) Spectrum of FBGs; (b) schematic of oscillator; (c) slope efficiency[33]

图 9. 实验结果。(a) 45°倾斜光栅插损与偏振相关损耗;(b)非线性偏振旋转锁模光路;(c)单孤子锁模光谱;(d)单孤子锁模自相关;(e)类噪声锁模光谱;(f)类噪声锁模自相关[34]

图 10. 实验结果。(a)逐面刻写光栅的光路;(b) type I型FBG光谱;(c)改变重复频率实现type I型CFBG刻写; (d) type II型FBG光谱[35]

Fig. 10. Experimental results. (a) Schematic of plane-by-plane inscription; (b) spectrum of type I FBG; (c) spectrum of type I CFBG; (d) spectrum of type II FBG[35]

图 11. 纤芯扫描技术。(a)示意图;(c)纤芯扫描与逐点刻写的FBG光谱对比[36]

Fig. 11. Core-scanning technology. (a) Schematic of core-scanning; (b) FBG spectrum comparison of core-scanning and point-by-point [36]

图 12. 不同方法刻写的CFBG。(a)逐点刻写;(b)纤芯扫描;(c)改进型纤芯扫描;(d)逐点刻写CFBG的光谱;(e)纤芯扫描刻写CFBG的光谱;(f)改进纤芯扫描刻写CFBG的光谱[37]

Fig. 12. CFBG written by different methods. (a) Point-by-point; (b) core-scanning; (c) modified core-scanning spectrum of CFBG by point-by-point; (d) spectrum of CFBG by core-scanning; (e) spectrum of CFBG by modified core-scanning[37]

图 13. 双芯少模光栅。(a)实验光路;(b)局部放大图[41]

Fig. 13. Twin-core FMFBG. (a) Experimental optical path; (b) partial enlarged view[41]

图 14. TMFBG。(a)刻写TMFBG示意图;(b)TMFBG光谱图[45]

Fig. 14. TMFBG. (a) Schematic of TMFBG inscription; (b) spectrum of TMFBG[45]

图 15. 实验结果。(a)保留涂敷层(蓝)与去除涂敷层(黑)的光谱;(b)斜率效率与实验光路[47]

Fig. 15. Experimental results. (a) Spectrum of FBG (blue is with coating, black is without coating);(b) slope efficiency and schematic of oscillator[47]

图 16. 在未去涂敷层的光纤上刻写FBG。(a)刻写光栅光路;(b)重复频率为1 kHz,曝光时间为5 min的光谱;(c)重复频率为500 Hz,曝光时间为10 min的光谱[49]

Fig. 16. Writing FBG on the optical fiber without decoating. (a) Schematic of FBG inscription; (b) spectrum of FBG with repetition rate 1 kHz and exposure time 5 min; (c) spectrum of FBG with repetition rate 500 Hz and exposure time 10 min[49]

图 17. 飞秒激光相位模板扫描技术。(a)相位模板扫描刻写示意图;(b)光栅透射谱以及透射深度随光栅长度的变化[50]

Fig. 17. Femtosecond laser phase template scanning technology. (a) Schematic of phase mask scanning technology; (b) transmission spectra and transmission over length[50]

图 18. 相位模板扫描技术。(a)掺铒光纤刻写FBG透射谱;(b)激光器示意图;(c)斜率效率[51]

Fig. 18. Phase mask scanning technology. (a) Transmission spectrum of FBG in EDF; (b) laser experiment setup; (c) slope efficiency[51]

图 19. 实验结果。(a) CFBG光谱;(b)激光器光路;(c)高功率激光器斜率效率[53]

Fig. 19. Experimental results. (a) Spectrum of CFBG; (b) laser experiment setup; (c) slope efficiency[53]

图 20. 实验结果。(a)内包层CFBG光谱;(b)激光器光路[54]

Fig. 20. Experimental results. (a) Spectrum of inner-cladding CFBG; (b) laser experiment setup[54]

表 1不同飞秒激光直写方式的对比

Table1. Comparison of various femtosecond laser direct inscribing methods

表 2相位模板刻写技术的对比

Table2. Comparison between phase mask writing methods

表 3国内外飞秒激光刻写光纤光栅的进展情况

Table3. Development of fiber gratings inscribed by using femtosecond laser

表 4飞秒激光直写与相位模板辅助刻写技术的对比

Table4. Comparison between direct inscribing and phase mask assisted writing

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基于飞秒激光刻写光纤光栅的研究进展下载： 2665次

图 1. 逐点刻写的包层模耦合情况^[18]

Fig. 1. Transmission spectrum of a point-by-point inscribed FBG^[18]

图 2. 采用逐点刻写的方法制备FBG。 (a)实验装置;(b)刻写在不同位置的不同周期光栅的显微图与光谱;(c)刻写在不同位置相同周期光栅的光谱^[21]

Fig. 2. FBG preparation by point-by-point writing. (a)Experimental device; (b) microscope images and reflection spectra of FBGs with different periods written in different positions; (c) spectrum of FBGs with the same period written in different positions^[21]

图 3. 在扭转的七芯光纤上刻写FBG阵列^[23]

Fig. 3. FBG array inscription in twist seven-core fiber^[23]

图 4. 采用逐线刻写的方法制备FBG。 (a)飞秒激光逐线刻写示意图;(b)四阶FBG显微示意图;(c)逐线刻写FBG透射谱^[24]

Fig. 4. FBG preparation by line-by-line writing. (a) Schematic of femtosecond laser line-by-line inscription; (b) microscopic of fourth-order FBG; (c) transmission spectrum of line-by-line inscribed FBG^[24]

图 5. π相移光栅。(a)光栅在不同偏振态下的透射谱;(b)不同扭转角下,P₁-P₂的变化曲线^[26]

Fig. 5. π phase shift grating. (a) Transmission spectrum of different polarization states; (b) curves of P₁-P₂ with different twist angles^[26]

图 6. 逐线刻写光栅阵列。(a) FBG阵列编码的3位二进制编码的示意图;(b)编码111的FBG阵列的后向散射^[28]

Fig. 6. Line-by-line writing grating array. (a) Schematic diagram of the encoded FBG array with a 3-bit binary coding; (b) backscattering of FBG array with code 111^[28]

图 7. 逐面刻写光栅阵列。(a) FBG阵列^[29];(b)倾斜角为7°的TFBG光谱^[30]

Fig. 7. Plane-by-plane writing grating array. (a) FBGs array^[29]; (b) TFBG spectrum with a tilt angle of 7°^[30]

图 8. 铒镱共掺的双包层光纤上刻写光栅对。(a)光栅光谱图;(b)振荡器光路;(c)斜率效率^[33]

Fig. 8. Grating pair on double-clad fiber co-doped with Er and Yb. (a) Spectrum of FBGs; (b) schematic of oscillator; (c) slope efficiency^[33]

图 9. 实验结果。(a) 45°倾斜光栅插损与偏振相关损耗;(b)非线性偏振旋转锁模光路;(c)单孤子锁模光谱;(d)单孤子锁模自相关;(e)类噪声锁模光谱;(f)类噪声锁模自相关^[34]

图 10. 实验结果。(a)逐面刻写光栅的光路;(b) type I型FBG光谱;(c)改变重复频率实现type I型CFBG刻写; (d) type II型FBG光谱^[35]

Fig. 10. Experimental results. (a) Schematic of plane-by-plane inscription; (b) spectrum of type I FBG; (c) spectrum of type I CFBG; (d) spectrum of type II FBG^[35]

图 11. 纤芯扫描技术。(a)示意图;(c)纤芯扫描与逐点刻写的FBG光谱对比^[36]

Fig. 11. Core-scanning technology. (a) Schematic of core-scanning; (b) FBG spectrum comparison of core-scanning and point-by-point ^[36]

图 12. 不同方法刻写的CFBG。(a)逐点刻写;(b)纤芯扫描;(c)改进型纤芯扫描;(d)逐点刻写CFBG的光谱;(e)纤芯扫描刻写CFBG的光谱;(f)改进纤芯扫描刻写CFBG的光谱^[37]

Fig. 12. CFBG written by different methods. (a) Point-by-point; (b) core-scanning; (c) modified core-scanning spectrum of CFBG by point-by-point; (d) spectrum of CFBG by core-scanning; (e) spectrum of CFBG by modified core-scanning^[37]

图 13. 双芯少模光栅。(a)实验光路;(b)局部放大图^[41]

Fig. 13. Twin-core FMFBG. (a) Experimental optical path; (b) partial enlarged view^[41]

图 14. TMFBG。(a)刻写TMFBG示意图;(b)TMFBG光谱图^[45]

Fig. 14. TMFBG. (a) Schematic of TMFBG inscription; (b) spectrum of TMFBG^[45]

图 15. 实验结果。(a)保留涂敷层(蓝)与去除涂敷层(黑)的光谱;(b)斜率效率与实验光路^[47]

Fig. 15. Experimental results. (a) Spectrum of FBG (blue is with coating, black is without coating);(b) slope efficiency and schematic of oscillator^[47]

图 16. 在未去涂敷层的光纤上刻写FBG。(a)刻写光栅光路;(b)重复频率为1 kHz,曝光时间为5 min的光谱;(c)重复频率为500 Hz,曝光时间为10 min的光谱^[49]

Fig. 16. Writing FBG on the optical fiber without decoating. (a) Schematic of FBG inscription; (b) spectrum of FBG with repetition rate 1 kHz and exposure time 5 min; (c) spectrum of FBG with repetition rate 500 Hz and exposure time 10 min^[49]

图 17. 飞秒激光相位模板扫描技术。(a)相位模板扫描刻写示意图;(b)光栅透射谱以及透射深度随光栅长度的变化^[50]

Fig. 17. Femtosecond laser phase template scanning technology. (a) Schematic of phase mask scanning technology; (b) transmission spectra and transmission over length^[50]

图 18. 相位模板扫描技术。(a)掺铒光纤刻写FBG透射谱;(b)激光器示意图;(c)斜率效率^[51]

Fig. 18. Phase mask scanning technology. (a) Transmission spectrum of FBG in EDF; (b) laser experiment setup; (c) slope efficiency^[51]

图 19. 实验结果。(a) CFBG光谱;(b)激光器光路;(c)高功率激光器斜率效率^[53]

Fig. 19. Experimental results. (a) Spectrum of CFBG; (b) laser experiment setup; (c) slope efficiency^[53]

图 20. 实验结果。(a)内包层CFBG光谱;(b)激光器光路^[54]

Fig. 20. Experimental results. (a) Spectrum of inner-cladding CFBG; (b) laser experiment setup^[54]