| 题名 | 1.57μm波段纳秒脉冲光参量放大技术研究 |
| 作者 | 李环环 |
| 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 | 朱小磊 |
| 关键词 | 差分吸收雷达 光学参量放大器 相位匹配 逆转换 光谱纯度 |
| 其他题名 | Research on nanosecond pulsed optical parametric amplifiers at 1.57μm |
| 中文摘要 | 主动探测大气CO2浓度的积分路径差分吸收激光雷达技术因其具有测量精度高、可全天候实时探测等优点而成为目前国内外激光大气环境监测研究领域的热点工作之一，已引起持续而广泛的关注。差分吸收激光雷达系统要求激光发射源具有优良的输出性能，不仅要保证良好的光谱特性，还要求高至几十毫焦的单脉冲能量和接近光学衍射限的光束质量等等。本论文研究工作主要针对差分吸收大气CO2浓度探测激光雷达的应用需求，开展了基于非线性晶体KTP和KTA的1.57μm波段窄线宽光参量放大器技术的研究，侧重解决大脉冲能量、高光谱特性、双脉冲输出（on-line/off-line）的激光发射源的部分关键技术。 论文研究工作的主要内容包括纳秒光参量放大技术的理论研究、窄线宽纳秒脉冲光参量放大器性能的原理性验证实验和参数优化设计、不同晶体OPA特性实验对比分析，以及单频双脉冲、双波长信号脉冲经过多级KTA-OPA装置放大后的激光输出性能变化规律的研究及原理样机研制等。 通过求解非线性方程组建立了纳秒脉冲OPA的数值解模型，获得了高斯光束的增益特性。针对未来的应用需求，通过对主要的几种非线性晶体的优缺点分析，确定KTA晶体作为获得1.57μm放大的OPA晶体，通过理论计算得到了对应的相位匹配调谐曲线。最后推导出在纳秒脉冲OPA系统中，泵浦光和信号光之间的线宽关系式，为泵浦光线宽指标设定给出理论指导。 介绍了KTP、KTA和YCOB三种非线性晶体光参量放大增益性能对比实验工作。 在试验搭建的KTA晶体光参量放大器的实验装置中，比较了采用非单频OPO信号光和单频OPO信号光作为初始信号光两种情况下的OPA增益特性，最终测试了OPA信号光光束质量。通过引入泵浦光延时机制，在KTA晶体OPA结构中，成功实现了重复频率100Hz，单脉冲能量大于98mJ的OPA1.57μm激光脉冲输出，脉冲宽度约为5.6ns，相应的泵浦光到信号光的转换效率达到26%。 开展差分吸收探测CO2浓度激光雷达激光双波长激光光源的研制工作。 采用课题组自行研制的50Hz重复频率单频双脉冲1.064μm脉冲激光振荡-放大器作为泵浦源，在线性排布的KTA-OPA装置中，成功实现了on-line和off-line双波长、双脉冲的单频种子注入和OPA高增益光放大。最终获得了单脉冲能量大于60mJ，光束质量 M2小于2.3的激光脉冲序列输出，放大后的信号脉冲在100s内的频率稳定性（rms）为0.71MHz，光谱线宽值小于50MHz，基本达到差分吸收激光雷达对激光性能参数的要求。 对OPA输出信号光的光谱纯度特性开展了初步的实验研究。在压强为30mbar下，采用一个等效光程200m长的CO2气体吸收池，搭建了测量系统，最终测得本论文设计的KTA-OPA系统最终放大输出的信号光的光谱纯度为99.92%。 |
| 英文摘要 | The Integrated Path Differential Absorption (IPDA) lidar technique is one of the important attractive researches on lidar application for actively remote sensing the concentrations of earth’s carbon dioxide. The advantages of this lidar system are that it can provide both day and night measurements and such an active concept can assure the observation of the entire atmospheric column with high accuracy. For the IPDA lidar, the laser transmitter must fufill the challenging requirement, such as excellent spectral stability and purity, pulse energy of tens mJ together with good beam quality and so on. To address the requirements, research on narrow band optical parametric amplifier based on nonlinear crystals of KTP and KTA at 1.57μm is carried out, focusing on solving some key technologies in the laser transmitter with high pulse energy and high spectral performance. The main context includes the numerical simulation of the nanosecond optical parametric amplifier, experimental research and parametric optimization on different optical parametric amplifiers, OPA performances comparation among different crystals, research on the output performance of the single frequency double pulse KTA-OPA and so on. A numerical model of nanosecond OPA is performed by solving the coupled differential equations which describes gain characteristics of Gaussian beams. For application requirements, considering the advantages and disadvantages of several major nonlinear crystals, the KTA crystal is used in the OPA obtaining 1.57μm and its phase-matching tuning curve is calculated. Finally the linewidth relationship between the pump light and signal light in a nanosecond OPA is deduced which gives theoretical guidance to determine the linewidth of the pump light. The OPA gain characteristics of KTP、KTA and YCOB are compared. Experimental research has focused on KTA optical parametric amplifiers and experiments are conducted with non-single-frequency and single-frequency OPO signal respectively. The OPA gain and the OPA signal beam quality is tested. A KTA-OPA configuration is designed by introducing a time delay between the pump and the signal. A gain of up to 98 at 1.572μm is obtained at frequency of 100Hz with a pulse width of 5.6ns and the corresponding conversion efficiency is 26%. The development of the laser transmitter for active remote sensing of CO2 is described. A linear arrangement KTA-OPA system pumped by a home-built single-frequency double-pulse Nd:YAG master oscillator power amplifier at 1064 nm successfully realize the output of on-line and off-line wavelength simultaneously with high gain. The main requirements for a differential absorption lidar transmitter can be achieved. 60mJ of signal pulse at 1.57 µm wavelength is generated with high beam quality of less than 2.3. The frequency stability of the final signal pulse is 0.71MHz rms in 100s and around 50 MHz linewidth of the signal pulse is achieved. Experimental study on the spectral purity (SP) of the OPA signal pulse is demonstrated. For the SP measurements, we use a multi-pass cell with an optical path length of 200m filled with pure CO2 typically at pressures of ~30mbar. A degree of the spectral purity of 99.92% is achieved for the final output signal. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15896]  |
| 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 | 李环环. 1.57μm波段纳秒脉冲光参量放大技术研究[D]. 中国科学院上海光学精密机械研究所. 2014. |
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