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题名	星载精密光谱测量用激光器稳频技术研究
作者	黄崇德
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	瞿荣辉
关键词	差分吸收激光雷达，大气垂直干涉仪，频率调制光谱稳频技术，多普勒吸收线，空芯光子晶体光纤
其他题名	Study of Laser Frequency Stabilization Technology Applied in Spaceborne Precision Spectroscopy Measurement
中文摘要	半导体激光器效率高，体积小，轻量化，十分适合空间环境应用。使用稳频技术对其进行控制，可以得到单频特性好，频率稳定性高的激光输出，在激光相干通信，卫星高分辨率光谱仪，星载激光大气环境要素探测，空间冷原子物理实验等前沿科学和空间技术领域有着重要的科学研究意义和明确的应用前景。本文针对星载环境应用的要求，对两种用于精密光谱测量技术的稳频激光器进行了深入研究。其中一个是用于高精度大气CO2浓度测量的差分吸收激光雷达（Differential Absorption Lidar，DIAL）技术中的种子激光器，另一个是用于地球大气红外辐射光谱测量的大气垂直干涉仪的基准光源。对于DIAL种子激光器，先后从理论模型，频率参考源部件，整体系统这三个层面进行了详细的分析，测试和研究。对于干涉仪基准激光器，针对其星载环境的工程应用设计和环境模拟测试进行了研究和介绍。本文的主要研究内容如下： 1. DIAL种子激光器 （1）针对DIAL的应用要求，对其种子激光器进行方案优化设计。根据DIAL种子激光器的工作原理，深入研究了频率调制光谱稳频技术的原理和CO2多普勒展宽吸收线的理论知识，建立了DIAL种子激光器实现稳频过程的数学模型。通过建模仿真分析了调制频率，调制深度，吸收池气压这三个系统工作参数对用于稳频反馈的误差信号的影响，得到了DIAL种子激光器最佳工作参数：调制频率145 MHz，调制深度3.5，吸收池气压70 mbar。对于后续激光器的研制工作有着重要的指导意义。 （2）针对星载环境的应用要求，设计并制作了体积小，轻量化，高可靠的空芯光子晶体光纤（hollow-core photonic crystal fiber, HC-PCF）吸收池，并对其进行了特性测试和研究。  针对HC-PCF吸收池存在透射谱噪声的现象，对现有的透镜耦合型，插芯对接型，熔接型三种结构的HC-PCF吸收池的透射谱进行了测试，分析确定其透射谱噪声是由背景振荡和法布里-珀罗（Fabry-Perot，FP）干涉条纹组成。  针对HC-PCF吸收池透射谱存在背景振荡的现象，对其形成机理进行了探索研究。通过对HC-PCF出光的光斑特性和模式特性进行测试，确认其光斑质心位置会随出光频率与光纤温度发生改变，其模式特性并非理想单模，还存在高阶模和表面模；随后根据测试结果建立了仿真模型进行理论分析，确认了只有非对称相位分布的高阶模与基模的空间干涉，才会导致光斑质心位置的变化，吸收池结构中有限的孔径结构起到空间滤波作用造成了额外的背景振荡噪声。  针对DIAL种子激光器对频率参考源低噪声的要求，探索研究低噪声HC-PCF吸收池的改进方案。根据仿真分析的结果与实验现象，通过缩短吸收池长度来增大背景振荡周期，改变入射光偏振态来调节透射谱平坦区位置，改变出光探测方式以避免空间滤波效果，尝试新的HC-PCF密封方式避免形成FP干涉条纹。测试结果表明，有望把HC-PCF透射谱的噪声幅度降低一个量级。 （3）研制了DIAL种子激光器的桌面系统样机。根据DIAL种子激光器工作原理，设计了光路结构，电子学部分，以及软件部分，搭建成桌面系统进行测试分析。  对比了仿真结果与测试数据，证明了DIAL种子激光器仿真模型的准确性。  针对HC-PCF吸收池透射谱中FP干涉条纹的干扰，提出一种简单有效的方法，成功克服了FP干涉条纹的影响。  为了考察不同结构的HC-PCF吸收池透射谱噪声的影响，把插芯对接型和熔接型HC-PCF吸收池应用于DIAL种子激光器中，对稳频性能进行测试分析，确认熔接型HC-PCF吸收池更适合作为频率参考源。  针对现有熔接型HC-PCF吸收池存在背景振荡的情况，采用高精度温控对HC-PCF吸收池进行控制，研究温度对HC-PCF吸收池以及电光相位调制器扰动的影响。  为了考察DIAL种子激光的频率稳定性，通过波长计测试和拍频测试的方法，对系统频率稳定性进行测试，证明了目前DIAL种子激光器的桌面系统可以在1.5小时内实现频率波动均方根值（root mean square，RMS）小于300 kHz，满足设计指标要求。 2. 干涉仪基准稳频激光器 （1）针对星载大气垂直干涉仪对基准光源体积小，轻量化，长寿命，高可靠的应用需求，对干涉仪基准稳频激光器进行了方案选定。选择了结构紧凑、集成度好的DFB激光二极管作为光源；选择工作波长为852 nm与Cs吸收峰匹配；选择自由空间光路以保证偏振状态稳定；选择无调制稳频技术在保证稳频精度的同时尽可能使设计简单，结构可靠。 （2）针对干涉仪基准稳频激光器的实际工程应用要求，对其装调过程，系统结构进行了研究设计。为了保证稳频结果的可靠性，具体设计了稳频策略，采用低频扫描吸收峰的方法把激光频率锁定在Cs吸收峰上；为了确保干涉仪基准稳频激光器的长寿命和可靠性，编写一套筛选测试软件对其光源DFB激光二极管进行了筛选测试；针对系统对光斑质量的要求，设计了激光器的光调过程，实现了光斑形心质心偏差小于0.2 mm，有效直径大于7 mm，发散角小于0.2 mrad，椭圆度优于0.85，指向偏差小于0.2 mrad的光束输出；为了保证出光功率的稳定性，通过测试分析，确定了反馈光会造成出光功率的波动，为此设计了一套调装流程，严格控制光的反馈量，提高出光功率的稳定度；为了在恶劣的星载环境中给激光器提供一个相对舒适的工作条件，对热控结构进行了设计，采用了双层材料结构的安装脚设计，调节激光器导热能力到一个合适的水平，结合主动温控的办法，保证了激光器在极高温和极低温情况下均能正常工作。 （3）为了验证干涉仪基准稳频激光器能在星载环境下正常工作，对其进行环境模拟测试。在力学振动试验中，通过观测随机振动的自功率谱和正弦振动的扫频信号，以及在试验前后对关键性能参数进行测试比对，证明其结构设计合理，工作性能良好可靠；在热真空试验中，监测激光器的出光频率，功率，指向以及热控状态，得到其激光频率变化量小于2×10-6，功率变化量小于5%，指向波动小于0.2 mrad，其它各项性能参数也均能满足工程应用的指标要求。证明该干涉仪基准稳频激光器能满足星载工程应用的各项要求。
英文摘要	The semiconductor laser diode is suitable for the space application for its advantages of highefficiency, small size and light weight. By applying the suitable frequency stabilization technology, it can produce the laser with single and stable frequency characteristics. It has significant meaning for the scientific research and clear application prospect in the areas of laser coherent communication, spaceboren high-resolution spectrometer, spaceboren atmospheric elements detection lidar, space cold atom physics experiment. This thesis focuses on the requirement of the space application and conducts the research on two kinds of frequency stabilized laser used in precision spectroscopy measurement. One of the frequency stabilized laser is used in the Differential Absorption Lidar (DIAL) for high-accuracy measurement of atmospheric CO2concentration, the other is reference light source of the Atmospheric Sounding Interferometer for measuring the Earth’s atmospheric infrared radiation spectrum. Detailed test, analysis and research of the theory model, the frequency reference device and the overall system are carried out for the DIAL’s seed laser. The engineering application design and environmental simulation testare introduced and studied for the interferometer reference laser.The main contents of the thesis are as follows: 1. The DIAL’s seed laser (1)In view of the DIAL’s application requirement, the optimal parameters of its seed laser is designed. A theory model for the DIAL’s seed laser is built according to the principle of the frequency modulation spectroscopy technique and the theory of CO2Doppler absorption line. The impacts of the modulation frequency, depth and gas pressure on the error signal are analyzed by the model simulation. And the optimal parameters are given as: 145 MHz for the modulation frequency, 3.5 for the modulation depth and 70 mbar for the gas pressure. These results have important guiding significance for the subsequent development work on the DIAL’s seed laser. (2) Inconsideration of the spaceboren application requirement. The hollow-core photonics crystal fiber (HC-PCF) gas cells with small size, light weight, and high reliability are designed and built. The further test and research are carried out.  In view of the HC-PCF gas cell’s transmission noise, the measurements on the transmission spectrum of the lens-coupled, ferrule-spliced and fusion-spliced HC-PCF gas cell are taken. The results show that the transmission noise is composed by the background oscillation and Fabry-Perot (FP) interference fringe.  In order to reduce the background oscillation of the HC-PCF gas cell’s transmission spectrum, the background oscillation’s formation mechanism is investigated. The variation of the spot’s center of mass (COM) with the laser frequency and fiber temperature is confirmed. HC-PCF has not only fundamental mode, but also the higher-order modes and surface mode. According to the test results, a simulation model is built. That the modes with asymmetric phase distributions affect the COM position is demonstrated. And the background oscillation is induced by the space-filter effect in HC-PCF gas cells.  In order to reduce the transmission noise of the HC-PCF gas cell, the improved solutions are explored. According to the earlier analysis results, the impacts of the length of the gas cell, the polarization state of the input light, the detection method of the output light and the processing method on the HC-PCF’s end on the transmission spectrum is test and analyzed. The results show that it’s possible to reduce the transmission noise by about one order of magnitude. (3) The desktop system of the DIAL’s seed laser is built. The optical structure, electronics part and software are designed according to the principle of the DIAL’s seed laser. And tests are carried out on the desktop system.  The test and simulation results are compared, and the accuracy of the simulation model is demonstrated.  In view of the existence of the FP interference fringe, a simple and effective method is proposed to avoid the disturbance successfully.  In order to study the impacts of different HC-PCF gas cells, the performances of the DIAL’s seed lasers using the ferrule-spliced and fusion-spliced gas cells are compared and analyzed. The better performance of the fusion-spliced gas cell is confirmed.  In view of the background oscillation, high accuracy temperature control is taken on the HC-PCF gas cell. The impact of the temperature disturbance on the HC-PCF gas cell and electro optic modulator (EOM) is study.  The frequency stability is measured by a wavelength meter and beat frequency test method and shows the root mean square (RMS) of the frequency fluctuation is less than 300 kHz within 1.5 hours. 2.Interferometerreference laser (1) In consideration of the Atmospheric Sounding Interferometer’s requirements as small size, light weight, long life-time, high reliability, the realization scheme of the interferometer reference laser is chosen. The small and compact DFB laser diode is selected as the source; the wavelength is set at 852 nm to match with the absorption line of Cs. The free space optical structure is designed to ensure the polarization state. The modulation free frequency stabilization technology is taken to ensure the frequency stability and simplify the laser design. (2) According to the engineering application requirement, careful design is taken on the adjustment process and laser structure. The laser frequency is locked on the Cs absorption line by low-frequency absorption line scanning method. The screening test software is written to take the screen on the DFB laser diodes. The optical adjustment process is designed and the spot’s centering error is less than 0.2 mm, effective diameter is lager than 7 mm, the divergence is less than 0.2 mrad, the ellipticity is better than 0.85, the pointing error is less than 0.2 mrad. Considering the impact of feedback light on the power stability, the control process of the feedback light is designed and the power stability is improved. Double-layer mounting feet is design, and the well thermal control of the interferometer reference laser is realized. (3) The environmental simulation tests are taken to verify the reliability of the interferometer reference laser working at the spaceboren environment. The mechanical vibration test and thermal vacuum test are taken and certifies that the design is reasonable and robust. The laser frequency fluctuation is less than 2×10-6, the power fluctuation is less than 5%, and the pointing variation is less than 0.2 mrad, other parameters all meet the targetrequirements.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15861]
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	黄崇德. 星载精密光谱测量用激光器稳频技术研究[D]. 中国科学院上海光学精密机械研究所. 2014.

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