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题名	空基小型高速调制与脉冲单频光纤激光器技术研究
作者	张鑫
学位类别	博士
答辩日期	2014
授予单位	中国科学院上海光学精密机械研究所
导师	陈卫标
关键词	人眼安全全光纤激光器 单频脉冲光纤放大器 受激布里渊散射 高速调制脉冲光纤放大器
其他题名	Study on spaceborne compact high modulation rate and single frequency pulsed fiber laser
中文摘要	本论文主要针对机载相干多普勒测风激光雷达和空间三维成像激光雷达的应用需求，进行脉冲单频光纤激光器和高重复频率窄脉冲全光纤激光器的理论和实验研究。 本论文的主要工作和创新点包括： 1.对半导体激光器脉冲调制方式进行研究，提出了脉冲光纤放大中种子源调制方式选择的依据。对脉冲光纤放大的增益特性及光纤放大中非线性效应进行理论分析，并归纳了抑制受激布里渊散射效应的方法。 2.根据远距离相干多普勒测风激光雷达的光源需求，创新性提出双声光级联调制脉冲和主增益光纤施加应力梯度的主振荡功率放大结构光纤放大方案，实现了高消光比和高脉冲能量的单频窄线宽脉冲激光输出。针对相干探测系统对脉冲对比度的要求，采用两个声光调制器级联调制后放大的方法，实现优于100 dB的消光比；针对脉冲单频放大中出现的受激布里渊散射效应、放大自发辐射及自激、脉冲波形畸变等问题进行了理论和实验分析，通过对主放大级增益光纤施加应力梯度、优化放大器各级增益及波形预补偿调制等方法，实现了重复频率10 kHz、脉冲宽度500 ns、激光线宽约1 MHz、光束质量因子Mx2=1.42, My2=1.13，单脉冲能量500 µJ的准单模高光束质量脉冲保偏激光输出，峰值功率达到1 kW，指标达到了国际领先水平，并成功应用在相干测风激光雷达中。 3.开展了单频单模脉冲光纤放大激光器研究，预放大级采用环形器和光纤光栅实现双程放大；在主放大级增益光纤上施加应力梯度，将光纤放大器受激布里渊散射阈值提高3.4倍，获得重复频率10 kHz、脉冲宽度200 ns、单脉冲能量72.3 µJ的衍射极限单频激光输出，Mx2=1.25，My2=1.18，峰值功率达到361 W，是目前10 µm纤芯硅基质单模光纤中得到的最高峰值功率。 4.选用光通信模块作为种子源产生高速伪随机码脉冲激光序列并结合光纤放大得到高功率高速伪随机码调制光源。为了抑制放大的过程中的自发辐射，将种子准连续放大后再用声光调制器斩波，同时对波形进行预补偿，所用伪随机码为11阶M序列，调制速率为1 Gbit/s，重复频率为10 kHz，在保持输出为平坦的伪随机码波形的基础上获得了42.5 dB的放大增益，输出峰值功率达到31.7 W。对不同长度的伪随机码光纤放大能力进行了研究。 5.研究了适用于三维成像激光雷达的高重复频率窄脉宽人眼安全全光纤激光器。种子源采用直接调制的半导体激光器，经两级光纤放大得到脉宽4.07 ns，重复频率200 kHz，峰值功率为1.02 kW的单模脉冲激光输出。
英文摘要	The thesis focus on the theoretical and experimental study of single frequency pulsed all fiber laser for airborne coherent Doppler lidar and high modulation rate narrow pulse width all fiber laser for spaceborne three dimensional imaging lidar. The main contents of thesis are presented as followings: 1.The pulse modulation types of laser diode, which is used as seed laser in master oscillator power amplification (MOPA) fiber laser, are discussed. We also do some research on the gain character and nonlinear effects in pulsed fiber amplification, especially the stimulated Brillouin scattering (SBS) effect. 2.A single frequency polarized eye safe all fiber laser with peak power over kilowatt for long-range coherent Doppler wind lidar is presented. We utilize two acoustic optics modulators (AOM) in MOPA configuration to enhance the pulse extinction ratio, which is vital for coherent detection, and get a extinction ratio over 100 dB. The power scaling in single frequency single mode fiber amplifier is mainly restricted by SBS, amplified spontaneous emission (ASE), parastic lasing and pulse distorion. Several ways are used to mitigate their influence such as applying longitudinally strain gradient on the gain fiber, optimizing gain allocation in each amplifier and utilizing pulse preshaping technology. Finally, A peak power of 1.08 kW and a pulse width of 500 ns at 10 kHz repetition rate with Mx2=1.42, My2=1.13 are achieved, which is the highest peak power with a linewidth of ~1 MHz in polarization-maintaining erbium-doped silica fiber to our knowledge. The laser has been employed in home-made coherent Doppler lidar system to measure long-range wind profile. 3.A single-frequency pulsed fiber laser based on standard single-mode polarization-maintaining fiber is also studied. Circulator and fiber Bragg grating (FBG) are utilized to realize double-pass amplification in the pre-amplifier. Longitudinally varied strains are applied on the gain fiber to realize approximately 3.4 times enhancement of the SBS threshold. Peak power of 361 W, pulse width of 200 ns at 10 kHz repetition rate are achieved with transform-limited linewidth. The beam quality is measured to be Mx2=1.25, My2=1.18. To the best of our knowledge, it is the highest peak power of an eye-safe, single-mode, narrow-linewidth, pulsed fiber laser based on 10 µm core diameter silica fiber. 4.An all fiber high modulation speed pseudorandom coded laser based on MOPA configuration is proposed. We use optical module of 1Gbit/s as the seed and modulate it into 11 order M-sequence pseudorandom pulse train. It is firstly quasi-continuously amplified to suppress the ASE. Then an AOM is added as pulse modulator to get 10 kHz repetition frequency and preshape the pseudorandom sequence. Finally, the peak power of pseudorandom code laser is amplified to 31.7 W without wave distortion, corresponding to a gain of 42.5 dB. We also compare the amplification ability of different pulse duration pseudorandom coded laser. 5.An eye safe, single mode, sub-Mega Hertz, nanosecond fiber laser is developed for three dimensional imaging lidar. The distributted feedback diode laser is directly modulated as seed then amplified by only two stage amplifiers. Peak power of 1.02 kW with 4.07 ns pulse duration at 200 kHz pulse repetition frequency with single-mode output is obtained.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15878]
专题	上海光学精密机械研究所_学位论文
推荐引用方式 GB/T 7714	张鑫. 空基小型高速调制与脉冲单频光纤激光器技术研究[D]. 中国科学院上海光学精密机械研究所. 2014.

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