单频脉冲全固态激光器种子注入技术研究
文献类型：学位论文
| 作者 | 张俊旋 |
| 学位类别 | 博士 |
| 答辩日期 | 2016 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 朱小磊 |
| 关键词 | 全固态激光器，单频，种子注入，电光相位调制器，Nd:YAG激光器 |
| 其他题名 | Research on injection seeding technology of single frequency pulsed all solid-state laser |
| 中文摘要 | 本论文以直接探测多普勒测风激光雷达和探测大气CO2浓度的差分吸收激光雷达对激光发射源的需求为背景，开展了激光雷达所需的单频脉冲全固态激光器的种子注入技术研究。论文通过对现有的种子注入方法进行优化，利用电光晶体代替传统的压电陶瓷实现快速调谐腔长，获得全固态激光器的单频脉冲稳定输出，同时实现了提高输出激光的频率稳定性和抗干扰能力的目的。技术突破对提升我国激光雷达光源的研制水平，进一步提升激光雷达整体性能具有现实意义。 本论文主要研究内容包括种子注入原理及其技术类别分析，LN晶体作为腔内相位调制器的种子注入技术实验研究，采用RTP晶体调谐腔长实现种子注入的单脉冲和双脉冲激光器实验研究。下面分章做简要介绍： 第一章阐述了选题的研究背景和意义，简要介绍了单频全固态激光器的实现方法，描述了单频全固态激光器的发展现状，最后引出了本文的主要研究内容。 第二章介绍了种子注入的基本工作原理；总结了实现种子注入的几种经典腔长控制技术，分别是建立时间最小化法、谐振探测法及其演化改进的技术，并对各个方案做了优缺点分析。现有的种子注入技术普遍采用压电陶瓷（PZT）机构调谐腔长。我们分析后认为，该技术欲进一步提升单频激光器的频率稳定性和工作重复频率具有局限性，尤其是针对未来的空间应用，PZT控制机构的使用寿命和可靠性问题将会成为制约。因此，阐述了利用电光晶体代替PZT调谐腔长实现种子注入的技术。采用非运动机构控制谐振腔长度是一种技术进步，也是种子注入技术的发展趋势。 第三章自行研制了基于铌酸锂晶体调谐腔长实现种子注入的单频脉冲激光器。设计了铌酸锂晶体用于调谐腔长的参数。将铌酸锂晶体插入双端抽运的种子注入Nd:YAG腔中。每个泵浦周期内，在铌酸锂晶体上施加线性斜坡扫描电压，通过调整从动腔中铌酸锂晶体的方向，使得外加电场不改变种子光的偏振状态，仅仅改变其相位，进而改变光学腔长。结合延迟-扫描-触发的种子注入技术，实现稳定的单纵模输出。实验得到激光重复频率为400 Hz，单脉冲能量为4.8 mJ，光束质量优于1.3，脉冲宽度约为25 ns，线宽约为21.2 MHz的单纵模输出。两分钟的频率稳定性和线宽稳定性分别为1.7 MHz和0.59 MHz。 第四章研制了基于RTP相位调制器的400 Hz和900 Hz的半导体激光器双端面抽运种子注入调Q Nd:YAG激光器。介绍了RTP晶体的物理特性和RTP晶体用于调谐腔长的设计。采用RTP电光晶体作为腔内相位调制器主动调谐腔长，实现单频种子注入，获得稳定的单纵模输出。采用另外一对RTP电光晶体作为调Q开关，在400 Hz重复频率下，利用单振荡级获得单脉冲能量为9.9 mJ，脉宽为16 ns的1064 nm激光脉冲序列输出。激光束在水平方向和垂直方向的光束质量M2值约为1.2。输出激光两分钟的频率稳定性为1.5 MHz，23分钟的能量稳定性优于0.3%。在900 Hz重复频率下，利用单振荡级获得单脉冲能量为7.5 mJ，脉宽约为14.6 ns，线宽为45 MHz的1064 nm激光脉冲序列输出。激光束在水平方向和垂直方向的光束质量M2值分别是1.30和1.36。输出激光两分钟的频率稳定性为1.1 MHz，线宽稳定性为0.52 MHz。在传导冷却结构中，实现了高频率稳定性和线宽稳定性的窄线宽单频脉冲激光的稳定输出，满足多普勒测风激光雷达的应用需求。 第五章针对测量CO2浓度分布的差分吸收激光雷达系统发射源对1 μm单频双脉冲激光器的应用需求，开展种子注入单频电光调Q Nd:YAG双脉冲激光器的研究工作。第一部分，采用两块压电陶瓷来控制腔长，一块压电陶瓷扫腔，另一块压电陶瓷施加反馈。采用带偏压反馈的谐振探测技术路线实现种子注入。利用一对温度补偿的RTP调Q开关，激光器输出脉冲能量达到10 mJ，脉冲宽度约为20 ns，重复频率为50 Hz。激光束在水平方向和垂直方向的光束质量M2值分别是1.31和1.36。在平均输出功率为1.035 W的条件下，60分钟的功率稳定性的均方差值为0.004 W。45分钟的频率稳定性的均方差值为4 MHz。第二部分，介绍了采用电光晶体扫描反馈腔长实现种子注入双脉冲激光器的技术方案。该方案有望进一步提高双脉冲激光器的能量稳定性和频率稳定性。此单频双脉冲激光器可以用作为测CO2浓度的差分吸收雷达系统的可靠泵浦源。 论文最后对实验研究工作进行简要总结，并对下一步的实验工作进行展望。 |
| 英文摘要 | The background of this thesis is based on the direct detection Doppler wind lidar and CO2 differential absorption lidar (DIAL). As a critical element of lidar, the laser transmitter is required to generate single-frequency pulse with high frequency stability. We carried out the research of the injection seeding technology of the single-frequency pulse all-solid-state laser，and improved the existing injection seeding technology by adopting an electro-optic crystal instead of traditional piezoelectric ceramic (PZT). Stable single frequency all solid state laser pulse was obtained, and meanwhile, we got higher frequency stability and better immunity of noise. Technological breakthrough is significant to promote the development of lidar. This thesis mainly includes three parts: the principle of the injection seeding, the experiments of using an LN crystal as a phase modulator to realize injection seeding, and the experimental study of single pulse and double pulse laser realized by using RTP crystal modulating the cavity length. The brief introductions are as follows: The first chapter elaborated the research background and the significance of this research. We also briefly introduced the methods to realize the single-frequency solid-state laser and described the development of single-frequency solid-state laser. Finally led to the main research content of this article. The second chapter presented the basic working principle of the seed injection. Several methods have been designed to ensure the resonance condition, such as the build-up-minimizing technique, the ramp-and-fire technique and so on. In those techniques, modulation of the optical path length of the slave cavity is usually carried out by two approaches: one is using a piezo-electric transducer to dither the rear mirror of cavity, and the other is applying an intracavity electro-optic phase modulator. As we known, the latter offers several advantages, such as completely eliminating the mechanically moving of the rear-mirror attached to PZT, solving the problem of nonlinear moving of the electromechanical components, etc. The using of intracavity electro-optic crystal phase modulator could achieve excellent frequency stability from an injection seeded laser due to its precise feedback on optical path length of the cavity. Therefore, using the electro-optic phase modulator to control cavity length is a technological progress and also a trend of the injection seeding technology. In chapter three，a reliable single frequency Q-switched Nd:YAG laser was developed by using an lithium niobate (LN) crystal as the intracavity phase modulator. The physical characteristics of LN crystal and design of LN crystal used to modulate the cavity length were introduced. Successfully injection seeding was performed by adopting an lithium niobate crystal to modify the optical path length and compete feedback control of the slave laser cavity in an effectively simplified cavity arrangement. Combination with a double-crystal RTP Q-switcher, the output pulse energy up to 4.8 mJ was obtained at a repetition rate of 400 Hz. The beam quality factor M2 was less than 1.3. The pulse duration was around 25 ns and the pulse spectrum was about 21.2 MHz. The shift of beat frequency was around 1.7 MHz (RMS) over 2 minutes and the linewidth stability was 0.59 MHz (RMS) over 2 minutes. In chapter four, a stable single-longitudinal-mode nanosecond pulsed 400 Hz and 900 Hz Nd:YAG laser with LDs dual-end-pumping arrangement were constructed. The physical characteristics of RTP crystal and design of RTP crystal used to modulate the cavity length were reported. Injection seeding was performed successfully by utilizing an RbTiOPO4 crystal as the intracavity phase modulator to change the optical length of the slave cavity based on the delay-ramp-fire technique. The laser generated 9.9 mJ pulse energy with 16 ns pulse duration at 400 Hz repetition rate. A near-diffraction-limit laser beam was achieved with beam quality factor M2 of approximately 1.2. The frequency jitter was 1.5 MHz over two minutes and the fluctuation of output pulse power was 0.3% over 23 minutes. Even more, in this experimental arrangement, stable SLM operation was also achieved when the repetition rate was increased to 900 Hz. Adopting a pair of RTP crystals as a Q-switcher, the laser was capable of generating 1064 nm wavelength, 7.5 mJ pulse-energy, 14.6 ns pulse duration and 45 MHz linewidth. The beam quality M2 of 1.30 in the horizontal direction and 1.36 in the vertical direction was obtained. The frequency stability was 1.1 MHz and the linewidth jitter was 0.52 MHz over two minutes. In conductively cooled structure, single-frequency laser with narrow linewidth, high frequency stability and high linewidth stability was obtained. In chapter five, an LD dual-end-pumped injection-seeded single-frequency double-pulse Q-switched Nd:YAG laser was developed and demonstrated based on the requirement of DIAL. In first part，a modified ramp-fire technique was applied to achieve reliable single longitudinal mode double-pulse laser output using PZT to modulate the cavity length. By using a double-crystal RTP electro-optic modulator, the output energy up to 10 mJ and the pulse width of nearly 20 ns were obtained at a repetition rate of 50 Hz. The measured M2 values were around 1.31 in the horizontal direction and 1.36 in the vertical direction when the total output energy was 20 mJ. The double-pulse power variation over 60 minutes was detected. The mean value of total output power was 1.035 W, and the fluctuation of output power was around 0.004W (RMS). The double-pulse frequency stability over 45 minutes was 4 MHz (RMS). In second part, injection seeding double pulse laser was designed by utilizing an RTP crystal to change the optical length of the slave cavity based on the delay-ramp-fire technique, which was expected to improve the energy stability and frequency stability of double pulse laser. This single-frequency double-pulse Q-switched laser is expected to be a good candidate for pumping source of DIAL systems for CO2 detection. Finally, a conclusion of this research was made and suggestion of the further work was introduced. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15991]  |
| 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 | 张俊旋. 单频脉冲全固态激光器种子注入技术研究[D]. 中国科学院上海光学精密机械研究所. 2016. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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