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题名	空间冷原子钟用DBR 激光器稳频及移频技术研究
作者	孙延光
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	冷原子钟 DBR 激光器 激光器稳频 快速移频 偏振旋转反馈 瓦斯遥测
其他题名	Study on DBR Laser Frequency Stabilizaiton and Shifting Technology Applied in Space Cold Atom Clock
中文摘要	冷原子钟以其高度稳定性和准确性为人类的科学技术活动提供了精密的时间频率标准，太空的微重力环境可以使冷原子钟的精度进一步提高，这对于基础科学研究、导航及深空探测等领域具有重要的意义。冷原子钟的一个关键的组成部分是其光源系统，必须具有窄线宽、高频率稳定性及快速移频性能。本论文的研究目标是研制一套用于空间环境的Rb87冷原子钟的光源系统，包括两台激光器，除上述性能要求外，还必须在恶劣的空间环境下连续稳定可靠的运行，基于此，本论文进行了如下的研究工作： 综合考虑激光器线宽、出光功率、体积、抗震性能等，选取分布布拉格反射（DBR）激光器作为光源，并采用波长调制饱和吸收光谱技术对其稳频，其中一台激光器负失谐稳定在Rb87的52S1/2→52P3/2跃迁的F=2→F’=2和F’=3的交叉共振峰上，用于产生Rb87原子冷却需要的冷却光、选态光和探测光；一台稳定在Rb87的52S1/2→52P3/2跃迁的F=1→F’=1和F’=2的交叉共振峰上，用于产生Rb87原子冷却所需的重泵浦光。稳频后的激光器线宽均小于1 MHz，两台激光器12 小时拍频频率波动峰峰值小于200 kHz，拍频数据在1 s积分时间的Allan方差为1.8×10-11，可以连续52 小时以上稳频不失锁，满足应用需求。 针对重泵浦激光器饱和吸收峰较弱的问题，实验研究了不同的泵浦光和探测光功率配比的情况下，饱和吸收峰的强弱和对比度，得到了一个优化的光功率配比，提高了重泵浦激光器的稳频性能。 针对快速移频的应用需求，提出了在移频中采用频率预补偿技术，保证出射光功率需求的基础上，实现了激光器60 MHz/ms的快速移频而不失锁；提出了一种快速扫描电流的移频方案，解决了声光调制器（AOM）移频对误差信号的干扰问题，达到了同样的技术指标。 针对空间应用的恶劣环境及无人管理性，对其关键元器件进行测试和筛选，研究影响误差信号信噪比的各种因素，同时还对整个光源系统的热力学性能进行了测试，设计了一套自动化激光器控制软件，提高了光源系统的稳定性和可靠性。 研制的光源系统已经成功的应用于Rb87原子冷却，得到了原子钟所需要的标志性的Ramsey条纹。 由于半导体激光器被高频调制时存在相位反转，传统的电学负反馈稳频技术的反馈带宽难以进一步提高，因此为了克服这一劣势，本文还进行了基于原子饱和吸收光谱和偏振旋转反馈技术用于半导体激光器稳频的探索性研究工作。利用133Cs原子的饱和吸收峰作鉴频元件，实现了将DFB激光器的频率稳定在133Cs原子的饱和吸收峰上，频率稳定性由自由运转的96 MHz提高到6.6 MHz，同时实现了线宽压窄效果，由自由运转的22 MHz压窄到550 kHz。相对于传统电学负反馈稳频技术具有高反馈带宽的优势。 本论文的最后一部分工作为基于数字反馈稳频的便携式激光瓦斯遥测技术。采用数字反馈稳频技术，将DFB激光器稳定在CH4分子的多普勒吸收峰上，在电流反馈的同时进行温度反馈，解决了瓦斯浓度测量的重复性问题，研制出了原理性样机。
英文摘要	Cold atom clock can supply a precise time and frequency standard for its high frequency stability and accuracy, playing an important role in the scientific and technical research. While in the microgravity space, the stability and accuracy of cold atom clock will be further improved, which is of great significance for fundamental scientific research, navigation, deep space exploration, etc. The laser system is one of the key components of the cold atom clock, which should have the characteristics of narrow linewidth, high frequency stability and rapid frequency shifting. The object of the thesis is to develop a laser system for Rb87 cold atom clock applied in space, which consists of two lasers. Besides the requiements of the above characteristics, it should work continuously in space with high stability and reliability. According to these requirements, the main contents are as follows: Due to the narrow linewidth, high output power, small volume and anti-vibration, distributed Bragg reflector (DBR) laser is selected as the laser source, and wavelength modulation saturated absorption spectroscopy (WM-SAS) is adopted to lock the frequency of the laser. One of the laser is locked to the F=2→F’=2,3 crossover resonance of the Rb87 transition 52S1/2→52P3/2, which is used to produce the cooling light, selection light and detection light used in different stage of the clock’s running process. Another is locked to the F=1→F’=1,2 crossover resonance of the Rb87 transition 52S1/2→52P3/2, which is used to produce the repumping light. The linewidths of the two frequency locked lasers are both less than 1 MHz. The peak to peak fluctuation of the beat frequency of the two lasers is less than 200 kHz during 12 hours, and its root Allan deviation is 1.8×10-11 at an averaging time of 1 second. The lasers can keep in lock state for more than 52 hours. All of the above characteristics can meet the practical requirements. In order to solve the problem that the SAS of the hyperfine transition F=1→F’=0,1,2 of the Rb87 is weak, the dependence of power ratio of pump beam to probe beam is investigated experimentally. An optimum power ratio is acquired; hence, the frequency stability of repump laser is effectively improved. According to the demand of rapid frequency shifting, a novel frequency pre-compensation technique is proposed, which can make sure that a tuning speed of 60 MHz/ms is achieved without losing lock and much power loss. Another rapid current scanning technique is proposed, which can solve the problem of signal to noise (SNR) degradation induced by acousto-optic modulator (AOM). This alternative can also achieve the same target. Due to the severe environment and unattended operation in space. The key components of the laser system are carfully tested and selected. The influence of several factors on the SNR of the error signal is studied in details. The thermodynamic property of the laser system is tested. Moreover, robust automation controlling software is developed. Therefore, the stability and reliability are improved. The developed laser system has been successfully applied in laser cooling of Rb87, and the Ramsey fringe has been obtained. As we know, phase inversion is a problem of most diode lasers modulated by high frequency, which would limit the feedback bandwidth of electrical negative feedback technique; therefore, an exploratory research on frequency stabilization technology based on SAS and polarization rotated optical feedback method is carried out. Using the SAS of the 133Cs-D2 line as the frequency discriminator, the DFB laser is frequency stabilized to the SAS of the 133Cs-D2 line. The frequecny fluctuation is reduced from 96 MHz of free-running to 6.6 MHz of stabilized case, and the linewidth is simultaneously reduced from 22 MHz to 550 kHz. Compared to the conventional electrical negative feedback technique, the proposed technique has the merit of high feedback bandwidth. Portable laser methane remote sensing technology based on digital feedback frequency stabilization is another part of this thesis. The DFB laser is frequency locked to the Doppler absorption peak of CH4. Current and temperature dual-feedback strategy can effectively improve the repeatability of the measured concentration. A principle prototype is developed.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/15890]
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	孙延光. 空间冷原子钟用DBR 激光器稳频及移频技术研究[D]. 中国科学院上海光学精密机械研究所. 2014.

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