| 题名 | 高稳定度可调谐外腔半导体激光器及无调制稳频技术研究 |
| 作者 | 魏芳 |
| 学位类别 | 博士 |
| 答辩日期 | 2013 |
| 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 | 外腔半导体激光器 无跳模调谐 无调制稳频 高稳定性 |
| 其他题名 | Study on High-Stable External Cavity Diode Lasers and Modulation-Free Frequency Stabilization Technology |
| 中文摘要 | 可调谐单纵模外腔半导体激光器具有线宽窄、调谐范围宽、结构紧凑、效率高、寿命长等优点，在冷原子物理、量子频标、高分辨率激光光谱、量子操纵、气体检测等领域具有十分广泛的应用。近年来由于空间及工程应用提出的严苛要求，激光器的环境适应性及长期可靠性已经成为与工作性能同等重要的设计特性，因此构建高稳定度的外腔半导体激光器具有十分重要的学术意义及实用价值。同时在激光冷却原子实验和原子频率及时间标准等领域中需要将激光器的频率稳定在原子的饱和吸收峰上，因此有许多稳频技术被不断提出并成功实现，但寻找简单、高效、抗扰性好的新型稳频技术仍然是当前的发展目标。本论文工作以构建高可靠性的可调谐光栅反馈外腔半导体激光器为目标，并在此基础上展开了基于87Rb的D2饱和吸收谱的新型无调制稳频技术的研究。主要内容包括： 1. 针对空间冷原子物理研究对可调谐窄线宽激光器的长期可靠性需求，采用星形柔性铰链调谐机构和一体化结构，研制了一种具有高稳定度的机械调谐式外腔半导体激光器。采用有限元分析计算方法对星形柔性铰链调谐机构进行了应力形变及模态分析，获得了优化设计参数，实现了高达3.7 kHz的基模共振频率，极大提高了无跳模调谐转动轴的力学稳定性，克服了现有机械调谐式外腔半导体激光器由于转动机构基模共振频率过低导致的抗振动性能和长期稳定性差的缺点。根据无跳模调谐条件，采用标量衍射理论对激光腔结构参数进行了设计，获得了无跳模调谐范围大于80 GHz、线宽为200 kHz的窄线宽单纵模激光输出。同时，对该激光器进行了稳频性能测试，将激光器锁定在87Rb的饱和吸收峰上，频率稳定度可达到3.5×10-11，可满足冷原子实验的应用需求。该激光器设计紧凑坚固，其各项参数指标已达到国际同类型激光器先进水平。 2. 设计和实现了一种无机械运动部件的新型电光调谐外腔半导体激光器。采用镀三角电极的高电光系数锆钛酸铅（PLZT）陶瓷材料作为腔内偏转器件，利用其二次电光效应产生光束的偏转从而实现波长的大范围快速调谐。通过改变偏转器的外加电压，该激光器在780.5 nm处实现了420 GHz的单纵模连续调谐，其电光调谐系数为840 GHz/kV。该项研究为进一步提高外腔半导体激光器的调谐性能和可靠性提供了新的技术途径。 3. 提出了一种基于相移Sagnac干涉仪的无调制稳频方案，通过在干涉仪内插入一个1/2波片使干涉仪内相反方向传输的两束光具有互相垂直的偏振态，并利用直角棱镜上发生的全内反射在干涉仪内引入一个相位差，通过探测干涉仪的输出信号得到饱和吸收峰附近的色散信息用以稳频。利用这种方案Littman-Metcalf型外腔半导体激光器的频率稳定在了87Rb (F=2→F′=2,3) 吸收峰上，将频率波动从8 MHz降低到了0.5 MHz。该方案无需对稳频光进行调制，光路结构简单，既保留现有Sagnac型无调制稳频技术的抗扰性好、偏振无关的优点，又避免了其利用高阶横模干涉存在的光路参数控制要求苛刻的缺陷。 4. 提出了一种基于全通型偏振分离Sagnac环的新型无调制稳频方案。该方案在稳频光进入Sagnac环之前加入1/4波片使稳频光转换为圆偏振光，并利用偏振分束器作为Sagnac环的输入输出端，使环内相反方向传播的两束光的偏振态互相垂直并存在π/2的相位差。通过偏振平衡探测的方法获得输出光的偏振变化情况进而得到饱和吸收峰附近的色散曲线。该方案同样实现了外腔半导体激光器的稳频，与前一种方法相比该方法光路更为简单，并且在同样的稳频光强下可获得更大幅度的误差信号，获得更好的稳频性能，有望在冷原子物理、冷原子钟等领域得到实际应用。 |
| 英文摘要 | Single-mode tunable external cavity diode lasers (ECDLs) have narrow linewidth, wide tuning range, compact structure, high efficiency and long life. Owing to these advantages, ECDLs become the key devices in a variety of applications, such as cooling atoms, quantum frequency standards, high-resolution laser spectroscopy, quantum manipulation, gas detection. In recent years, due to the stringent requirements of space and engineering applications, environmental adaptability and long-term reliability of the ECDLs have become as important as performance characteristics, so it has both great academic significance and practical value to design and built stable ECDLs. Meanwhile, the laser frequency needs to be stabilized on the saturated absorption peak of the atoms in the field of laser-cooled atomic experiments, atomic frequency and time standards, therefore many frequency stabilization methods have been proposed. But the researchers are still looking for simple, efficient, robust and novel frequency stabilization methods. This dissertation is mainly focused on building grating-feedback tunable ECDLs with high reliability, and its modulation-free frequency stabilization based on D2 saturated absorption spectrum of 87Rb. The main contents are as follows: 1. In view of the requirements of the space application in laser cooling area, the narrow-linewidth tunable lasers must have long-term reliability. A high-stable mechanical tuning ECDL based on a star-flexure hinge and integrated structure is realized. The existing mechanical tuning ECDLs mostly have poor performance in anti-vibration and long-term stability, due to the low fundamental resonance frequency of the rotating mechanism. To overcome these shortcomings, the stress deformation and modal analysis of the star-flexure hinge rotating mechanism are calculated by using finite element analysis method, and the design parameters are optimized to enhance the fundamental resonance frequency to3.7 kHz, meanwhile the mechanical stability of the pivot point is greatly improved. According to the mode-hop free tuning condition, the laser cavity structure parameters are designed using scalar diffraction theory, as a result, the ECDL offers single-mode operating with a linewidth of 200 kHz and a mode-hop free tuning range over 80 GHz. Meanwhile, the frequency of ECDL can be locked to the saturated absorption peak of 87Rb, and the frequency stability reaches 3.5×10-11, which can meet the application requirements of the cold atom experiments. Ultimately, the ECDL is compact and robust design, and the parameters have reached the international advanced level compared to other similar type of ECDLs. 2. A novel electro-optical tunable ECDL with non-mechanical moving parts is proposed and demonstrated. It uses an electro-optical deflector fabricated by PLZT electro-optic ceramic with high quadratic electro-optic effect as a wavelength tunable element to realize a fast and wide-range tuning. By adjusting the voltage applied to the deflector, a large single-mode tuning range of 420 GHz (including mode hops) and a frequency-voltage tuning ratio of 840 GHz/kV have been achieved at 780.5 nm. This study provides a new technical approach to further improve the tuning performance and reliability of the ECDLs. 3. A modulation-free frequency stabilization technique based on a phase difference biased Sagnac interferometer is proposed. A half wave plate and a total internal reflection prism are inserted into the loop to provide a phase difference bias between clockwise and counter-clockwise beams with perpendicular polarizations, and dispersion information near the saturated absorption peak can be obtained by detecting the output signal of the interferometer. By using this technique, the frequency of Littman-Metcalf configuration ECDL is locked at the transition of Rb atomic vapor, and the frequency fluctuation is suppressed from 8MHz to less than 0.5MHz peak-peak. This scheme is simple and modulation free, further more it retains the advantages of existing Sagnac modulation-free frequency stabilization technology, such as robust and polarization-independent, but also avoid the strict requirement of the optical path parameter control induced by the higher-order transverse mode interference. 4. A novel frequency stabilization method for ECDLs by using an all-pass polarization-split Sagnac loop is proposed. This scheme uses a quarter waveplate to convert the incident beam to a circularly polarized beam and a polarization beam splitter (PBS) for the input and output of the Sagnac loop, an phase difference bias of π/2 is introduced between clockwise and counter-clockwise beams with perpendicular polarizations. The dispersion phase shift induced by Rb saturation absorption can be obtained by balanced polarization divided detection of the Sagnac loop output beam. Frequency stabilization is realized by this method, and comparing to the first method, this method is simpler and can get larger error signal amplitude in the same experimental condition. This scheme is promised to be used in variety of related atomic physics experiment. |
| 语种 | 中文 |
| 内容类型 | 学位论文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/15732]  |
| 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 | 魏芳. 高稳定度可调谐外腔半导体激光器及无调制稳频技术研究[D]. 中国科学院上海光学精密机械研究所. 2013. |
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