星载激光雷达激光频率精密控制技术研究
文献类型：学位论文
| 作者 | 杜娟 |
| 文献子类 | 博士 |
| 导师 | 陈卫标 |
| 关键词 | 频率调制光谱稳频，光学锁相环，1572nm种子激光器，1064nm种子激光器，IPDA激光雷达，高光谱分辨率激光雷达 Frequency-modulation spectrum stabilization, Optical phase-locked loop, 1572nm seed laser, 1064nm seed laser, IPDA lidar, High spectral resolution lidar |
| 其他题名 | Study of Precise Laser Frequency Control Technology Applied in Spaceborne lidar |
| 英文摘要 | 近年来，随着工业化进程的不断发展，大气温室气体浓度的升高、雾霾现象的加剧，使人类的生存环境变得更加恶劣。CO2、气溶胶分别作为温室气体、雾霾的主要成分，影响着全球气候及人类健康，其浓度及分布的精确探测日益重要。星载激光雷达以其可全球，全天，高精度探测等优点为CO2和气溶胶探测提供了有效手段。本人所在实验室正在研制一套多波长激光雷达，可同时输出波长为1572nm、1064nm及532nm的脉冲激光，计划同时测量大气CO2柱状浓度及气溶胶光学厚度。测量CO2浓度采用积分路径差分吸收（IPDA）的方法，气溶胶光学厚度探测采用高光谱分辨率的方法。两种探测方法均需要高频率稳定高能量的单纵模脉冲激光光源。这种光源目前一般采用种子注入技术或者主振荡-功率放大器（MOPA）放大获得。因此种子激光器的频率稳定性对激光雷达探测CO2及气溶胶浓度来说至关重要。本文针对多波长激光雷达的1064nm、1572nm两个种子激光器的频率稳定性进行了研究。从稳频理论模型、分子谱线模型、稳频系统、频率稳定相关实验四个方面对种子激光器稳频进行了详细的分析、测试和研究。利用该稳频激光器构建了一套IPDA激光雷达CO2浓度探测地面验证装置，对其原理、系统、实验结果进行了详细的介绍和研究。本文的主要研究内容如下： 1、1572nm种子激光器的频率稳定性 （1）针对星载IPDA测量CO2浓度的应用要求，对其1572nm种子激光器的稳频系统进行了优化设计。本文梳理了用于online、offline激光器稳频的光学锁相环技术原理，用于参考激光器稳频的频率调制光谱技术的方法和理论基础。建立了用于参考激光器实现稳频的数学模型，通过建模仿真分析了吸收池气压，调制频率，调制深度对用于稳频反馈的误差信号的影响，得到了用于参考激光器稳频的最佳工作参数：调制频率130MHz，调制深度2.4，吸收池气压40mbar。对后续参考激光器的设计提供了重要指导。 （2）研制了IPDA种子参考激光器的系统样机，详细介绍了其光学部分，电子学部分，软件部分，并在样机的基础上进行了相关测试。对比了仿真结果与测试数据，证明了建立的参考激光器稳频数学模型的正确性。针对自由空间吸收池和电光相位调制器内存在的多光束干涉（MPI）效应引起的干扰，提出了一种简单且有效的方法抑制MPI噪声的影响。通过拍频的方法进行了频率稳定性测试，证明了该参考激光器在24小时监测时间内实现了频率波动均方根值小于25.6kHz，在积分时间10000s处阿伦方差值小于1×10-10，长期频率稳定性满足了设计指标。针对稳频激光器工作环境温度剧变引起的频率跳变现象，研究了系统中电学、光学器件的性能随环境变化引起的激光频率抖动误差，提出了对各器件工作环境的需求。 （3）在种子参考激光器实现频率稳定后，研制了种子online、offline激光器的锁频，介绍了锁相系统的光学部分，电子学部分，软件部分，通过拍频的方法对其进行了频率稳定性测试，证明了online与offline激光器在1h监测时间内实现了频率波动均方根值小于300kHz，满足了设计指标。 2、1064nm种子激光器的频率稳定性 （1）针对星载高光谱分辨率气溶胶探测的应用需求，对1064nm种子激光器稳频系统进行了优化设计。建立了基于频率调制光谱技术实现1064nm种子激光器稳频的数学模型，通过建模仿真分析调制频率，调制深度对用于稳频反馈的误差信号的影响，得到了用于1064nm种子激光器稳频的最佳工作参数范围：调制频率0.1-0.3倍的吸收线的多普勒半高宽度，调制深度2.2-2.8。对后续其稳频激光器的设计提供了重要指导。 （2）研制了1064nm种子激光器的系统样机，对其光学部分，电子学部分，软件部分进行了介绍，并在样机的基础上进行了相关测试。对碘分子的1109线线宽、PPLN的转换效率及温度特性进行了测试，对比了仿真结果与测试数据，证明了建立的1064nm种子激光器稳频数学模型的正确性。使用波长计对其频率稳定性进行了测量，证明了该激光器在30分钟内频率波动均方根值小于2MHz，满足了设计指标。 3、地面IPDA激光雷达CO2浓度测试 深入研究了IPDA激光雷达探测CO2浓度的反演算法。研制了一套地面IPDA激光雷达CO2浓度探测系统装置，针对激光发射单元、回波接收单元、数据采集与处理单元进行了介绍，并在系统装置的基础上进行了相关测试。通过注入offline-offline测试得到系统固定光学厚度误差为0.005。通过注入online-offine测试得到CO2浓度为432.71±2.42ppm，系统测量精度达到了0.56%，并与单点测试仪结果进行了比较。; In recent years, with the continuous development of industrialization, the increase in atmospheric greenhouse gas concentrations and the intensification of haze have made the living environment of humans worse. CO2、aerosols are the main component of greenhouse gases and haze respectively, affecting global climate and human health. The precise measurement of their concentration and distribution is increasingly important. The spaceborne LIDAR provides an effective means for their measurement with its global, all-day, high-precision detection and other advantages. My Laboratory is developing a multi-wavelength LIDAR with output wavelengths of 1572 nm, 1064 nm, and 532 nm, aiming to measure the concentrations of CO2 and aerosol simultaneously. Measure CO2 concentration using integrated path differential absorption (IPDA) method, aerosol optical depth detection using high spectral resolution method. Both detection methods require a single-longitudinal mode pulsed laser light source with high frequency stability and high energy. At present, this light source is generally obtained by seed light injection or master oscillator power-amplifier(MOPA) technology. Therefore, the frequency stability of seed laser is crucial for the LIDAR to measure CO2 and aerosol concentrations. In this thesis, the frequency stability of 1064nm and 1572nm seed lasers for multi-wavelength LIDAR were studied. The frequency stability of seed lasers were analyzed, tested and studied in four aspects: frequency stability theory model, molecular spectral model, frequency stabilization system, and frequency stability related experiments. A ground-based IPDA LIDAR for CO2 concentration detection using the 1572nm seed laser was built. The principle, system and experimental results were introduced and studied in detail. The main research contents of this article were as follows: 1、Frequency stability of 1572nm seed laser (1) According to the application requirements of the spaceborne IPDA LIDAR for CO2 concentration, the frequency stabilization system of 1572nm seed reference laser was designed optimally. The principle of the optical phase-locked loop for online and offline laser frequency stability was studied in depth, and the method and principle of the frequency-modulation spectroscopy technique for reference laser frequency stabilization were discussed in this thesis. A mathematical model was established for the reference laser to achieve frequency stabilization. The effect of the absorption cell pressure, modulation frequency, and modulation depth on the error signal used for frequency stabilization feedback were analyzed through simulation and modeling. And the optimum operating parameters for the reference laser frequency stabilization were obtained.They were modulation frequency of 130MHz, modulation depth of 2.4, absorption cell pressure of 40mbar respectively, providing important guidance for the design of subsequent reference lasers. (2) A system prototype of IPDA seed reference laser was developed. The optical part, electronics part and software part were introduced. And carry out some relevant tests on the basis of prototype.Through comparing the simulation results with the test data, the correctness of the established mathematical model for reference laser frequency stabilization was proved.Aiming at the interference caused by the multi-beam interference (MPI) effect existing in the free space absorption cell and the electro-optical phase modulator, a simple and effective method was proposed to suppress this influence. The frequency stability test was performed by the beat frequency method. It was proved that the reference laser achieved a root mean square (RMS) of frequency drift less than 25.6kHz in the 24h monitoring time, and the Allan variance was less than1×10-10 at the integration time of 10000s. The frequency stability meeted the design requirement.Aiming at the frequency hopping caused by the temperature change of the laser, the effects of electrical and optical device performance varing with environment on the stability of the laser frequency in the system were studied, and the requirements for the working environment of each device were proposed. (3) When frequency of the reference laser was stable, frequency-locking of online and offline lasers were developed. The optical part, electronics part, and software part of the system were introduced.Through the beat frequency method,it proved that the frequency stability of the online and offline lasers achieved the RMS of frequency fluctuation less than 300kHz in 1h monitoring time, which satisfied the design requirement. 2、Frequency stability of 1064nm seed laser (1) According to the application requirements of the spaceborne high spectral resolution aerosol detection LIDAR, the frequency stabilization system of the 1064nm seed laser was designed optimally. A mathematical model for frequency stabilization of the 1064nm seed laser based on frequency modulation spectroscopy was established. The effects of modulation frequency and modulation depth on the error signal used for frequency stabilization feedback were analyzed through simulation and modeling. And the optimum operating parameters range for the laser frequency stabilization were obtained.They were modulation frequency of 0.1~0.3 times Doppler halfwidth of absorption line, modulation depth of 2.2~2.8 respectively, providing important guidance for the design of subsequent seed laser. (2) A system prototype of 1064nm seed laser was developed. The optical part, electronics part and software part were introduced. And carry out some relevant tests on the basis of prototype.The 1109 line width of iodine molecule, double frequency conversion efficiency and temperature characteristics of PPLN were tested.Throught comparing the simulation results with the test data, the correctness of the established mathematical model for 1064nm seed laser frequency stabilization was proved. It was proved that the RMS of the frequency fluctuation of the laser was less than 2MHz within 30 minutes using a wavelength meter to measure its frequency stability, which satisfied the design requirement. 3、Ground IPDA LIDAR CO2 concentration test Study the inversion algorithm for CO2 concentration measurement by the IPDA LIDAR in depth. A ground CO2 concentration measurement IPDA LIDAR system device was designed. The laser emitting unit, echo receiving unit, data acquisition and processing unit of the LIDAR were introduced. And conduct some relative tests on the basis of the system installation. The fixed 0.005 optical thickness error of the system was obtained by the offline-offline injected test. The CO2 concentration was 432.71±2.42ppm obtained by the online-offine injected test, and the system measurement accuracy reached 0.56%. The results was compared with a gas analyzer of singal test. |
| 学科主题 | 光学工程 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/31046]  |
| 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 | 杜娟. 星载激光雷达激光频率精密控制技术研究[D]. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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