高功率激光驱动器前端系统关键技术研究
文献类型：学位论文
| 作者 | 乔治 |
| 文献子类 | 博士 |
| 导师 | 林尊琪 |
| 关键词 | 前端系统 Front-end system 幅频调制 FM-to-AM conversion 光纤放大器 fiber amplifier 时域相位 temporal phase 时域成像 temporal imaging |
| 其他题名 | Investigation on the key technologies of front-end in high power laser facility |
| 英文摘要 | 高功率激光驱动器前端系统需要为整个驱动器系统提供时间波形整形、光谱展宽、高精度同步的纳秒激光脉冲。在前端系统中为了获得稳定、高质量纳秒种子源，需要解决以下几个关键技术问题，包括幅频调制的抑制、毫焦耳光子晶体光纤放大器、纳秒激光脉冲非线性相移单次测量、皮秒脉冲波形高精度测量以及非线性相移单次测量以及非相干光源的产生。 本论文主要针对以上所述的高功率激光驱动器前端系统中关键技术问题进行研究，提出幅频调制抑制方法、高增益光纤放大器、纳秒和皮秒脉冲单次非线性相移测量方法、以及非相干锁模光纤激光器，针对这些方法进行了详细的理论以及实验研究，主要内容包括： 1. 理论研究前端系统中幅频调制的产生原理，建立了相关数值计算模型。利用该数值计算模型，分析了保偏前端系统、单偏振前端系统以及分布起偏保偏前端系统中幅频调制抑制的效果。结果表明基于单偏振光纤的单偏振前端系统理论上可以很好的抑制幅频调制的产生，提升幅频调制的稳定性。实验上搭建了单偏振前端系统，可以将幅频调制抑制在4%以下，同时幅频调制的稳定性控制在2%（峰峰值）。此外分析了单偏振前端系统中产生中心波长相关幅频调制的原因，并且提出了相关的解决方法。该研究结果表明单偏振前端系统是一种很好的解决高功率激光驱动器前端系统中幅频调制的方法，有望从根本上抑制幅频调制的产生，进一步提升前端系统性能。 2. 采用单模截止的光子晶体光纤实现了高增益、高光束质量的纳秒脉冲放大。通过数值模拟计算对比了光纤再生放大器与MOPA级联光纤放大器对纳秒激光脉冲的放大效果，发现光纤再生放大器的非线性相移（B积分）以及方波扭曲（SPD）更小。实验上采用纤芯直径40μm的光子晶体光纤的再生放大器实现了746μJ脉冲能量输出，增益达到60dB以上，同时光束为基横模输出。采用光纤模场直径为80μm的光子晶体光纤再生放大结构，进一步实现了1.2mJ脉冲能量放大，增益达到60dB以上，同时脉冲方波扭曲控制在3以下。该光纤再生放大器输出激光脉冲光束质量优良，接近衍射极限。此外还研究了空间结构以及全光纤结构MOPA级联光纤放大器，在实验中分别实现了400μJ以及890μJ脉冲能量放大，实现了高增益、低幅频调制、高光束质量的纳秒脉冲放大。 3. 针对纳秒窄线宽脉冲时域相位测量提出了时域剪切干涉方法。理论上分析了时域剪切干涉过程以及相对延时对时域剪切干涉的影响。实验上采用单次时域剪切干涉测量方法对高功率MOPA光子晶体光纤放大器放大后脉冲的时域相位进行测量，结果表明时域剪切干涉方法可以实现对纳秒激光脉冲的时域相位的准确测量，可以用于高功率激光驱动器系统中纳秒激光脉冲的非线性相移（B积分）的测量。 针对皮秒窄光谱激光脉冲，提出了时域模拟退火GS算法（AGS），该方法不但可以得到脉冲的振幅和时域相位，而且可以同时恢复测量过程中的激光脉冲的中心时间误差，减小测量误差对恢复过程的影响。在实验上使用该AGS算法和脉冲复制环结构对皮秒激光的时域非线性相移进行测量，测量结果与理论预测结果符合的很好，表明AGS算法结合脉冲复制环结构可以实现对皮秒脉冲的全域精确测量。 针对弱时域相位的测量，提出了时域扫描迭代恢复算法（TMPR），该方法可以实现时域上相位的扫描迭代恢复。通过模拟分析验证了该方法对于弱时域相位恢复的效果，并且得到了不同的参数对恢复效果的影响。该方法可以对时域剪切干涉方法与AGS方法进行补充，适合于弱时域相位纳秒脉冲的测量。 4. 基于时空对应性关系，提出采用时域成像过程实现对皮秒脉冲的高精度、大范围测量。理论上分析了时域成像过程，得到其时域成像条件，同时分析了基于光纤四波混频过程的时域成像过程。实验上采用高非线性光子晶体光纤，实现了基于四波混频过程的时域成像系统。使用该时域成像系统可以同时实现时频转换与时域放大过程。在时频转换过程中实现了340fs的时间分辨率，在时域放大条件下实现了380fs时间分辨率，同时测量范围可以达到80ps。 5. 针对前端系统中对非相干种子光的需求，采用NPR锁模方式，在双包层光纤锁模激光器中同时实现了Burst-mode锁模方式以及Noise-like锁模方式。在Burst-mode锁模状态下，实现了重复频率为196kHz的脉冲串输出，脉冲串包含55个子脉冲，其单脉冲能量达到12nJ。在Noise-like锁模状态下，输出纳秒方波锁模脉冲的脉冲宽度随着泵浦功率的增加可以从15.8ns到546ns之间连续调节，实现了目前NLP锁模脉冲的最大脉冲宽度。NLP锁模脉冲的能量可以达到820nJ，脉冲宽度为546ns。此外采用空间光谱滤波以及时域、光谱干涉的方式研究了NLP锁模脉冲的相干性，结果表明该双包层光纤锁模激光器输出的NLP锁模脉冲为非相干激光脉冲。; The front-end system of high power laser facility is responsible to provide temporally shaped, spectral broadened and precisely synchronized nanosecond seeding laser pulse. In order to obtain stable and high quality nanosecond laser, several key problems should be solved, including the suppression of FM-to-AM modulation, milli-joule photonic crystal fiber amplifier, single-shot measurement of the nonlinear temporal phase of picosecond and nanosecond laser pulses and the generation of incoherent laser. The work of this thesis mainly focuses on the suppression of FM-to-AM modulation and investigation on the photonic crystal fiber amplifier, and proposed several methods to measure the waveform and temporal phase of nanosecond and picosecond laser pulses. Also an incoherent mode-locked fiber laser is experimentally investigated. The main content consists several parts as follows: 1. The FM-to-AM modulation in the front-end system is theoretically analyzed and a numerical model is established. Using the numerical model, the PM fiber front-end, distributed polarizing PM fiber front-end and polarizing fiber front-end are compared respectively. The simulation results indicate that polarizing fiber front-end can successfully suppress the FM-to-AM modulation and improve the stability. According to the theoretical analysis, the polarizing fiber front-end is established experimentally and the experimental results show that the depth of FM-to-AM modulation can be reduced to 4% and also the stability can be controlled to be 2% (peak-peak). In addition the dependence of FM-to-AM modulation on the laser wavelength is investigated. The theoretical and experimental results indicate that the polarizing fiber is a great way to suppress FM-to-AM modulation to further improve the performance of laser front-end system. 2. Single-mode photonic crystal fiber is implemented to achieve high gain and high beam quality amplification. Numerical simulations are used to compare the performance of fiber regenerative amplifier and MOPA multi-stage fiber amplifier theoretically, which shows that the regenerative structure can provide laser pulses with smaller nonlinear temporal phase (B integration) and square pulse distortion (SPD). In the experiment, the regenerative amplifier with PCF fiber of a mode field of 40μm is established and the energy of the amplified laser pulse can be 746μJ corresponding to a total gain of 60 dB. Furthermore, the PCF rod fiber with a mode field of 80μm is used in the regenerative amplifier and the pulse energy can be 1.2mJ. In addition, the output laser which is nearly single-mode has a great beam quality and the SPD can be less than 3. Besides that, the spatial and all-fibered MOPA fiber amplifier are also investigated experimentally and the output pulse energy are 400μJ and 800μJ respectively. 3. In order to characterize the temporal phase of narrow-linewidth nanosecond laser, the temporal shearing interference (TSI) method is proposed. In this thesis, the TSI method has been analyzed theoretically. Also the TSI method is implemented to measure the nonlinear temporal phase in the high power fiber amplifier experimentally. The experimental results show a good performance and it can be concluded that the TSI method is suitable to measure the temporal phase in high power laser systems. The temporal annealing GS method (AGS) is also proposed to measure the full-field of picosecond pulses. The AGS method can not only recover the amplitude and temporal phase but also recover the measurement error of central time theoretically. The AGS method together with the pulse republication structure is used experimentally to characterize the picosecond laser and the recovered results match the theoretical value well. For the measurement of weak temporal, the temporal modulated phase retrieval (TMPR) method is proposed. The TMPR method is analyzed in the simulation and the results show good performance. This method can be used to characterize weak temporal phase which is quite important in high power laser systems. 4. Based on the space-time duality, the temporal imaging is used to achieve high resolution and large range measurement of picosecond pulses. The temporal imaging process based on four-wave mixing in fiber is theoretically analyzed. In the experiment, the temporal imaging system is realized using photonic crystal nonlinear fiber. And the temporal resolution of the time-frequency transfer and temporal magnification are 340fs and 380fs respectively. The measurement range can be 80ps which can be further increased. 5. A double-clading mode-locked fiber laser is established using NPR technique and the burst-mode and noise-like States can be both obtained in this structure. Under the Burst-mode state, the frequency of pulse train which is consisted with up to 55 pulses is 196 kHz and the single pulse energy is 12nJ. When the noise-like pulse state is achieved, the duration of square pulses can be tuned from 15.8ns to 546ns simply by pump powers and the maximum pulse energy is 820nJ. Also the coherence of NLP pulses are examined by spectral filtering and interference, which indicates that the NLP pulses are incoherent. |
| 学科主题 | 光学工程 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/30993]  |
| 专题 | 中国科学院上海光学精密机械研究所 |
| 作者单位 | 中国科学院上海光学精密机械研究所 |
| 推荐引用方式 GB/T 7714 | 乔治. 高功率激光驱动器前端系统关键技术研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
浏览0
下载0
收藏0
其他版本
除非特别说明，本系统中所有内容都受版权保护，并保留所有权利。