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连续激光光腔衰荡法精确测量高反射率研究
Alternative TitleContinuous-wave cavity ring-down technique for accurate measurement of high reflectivity
龚元
Subtype博士
Thesis Advisor李斌成
2008-06-11
Degree Grantor中国科学院光电技术研究所
Place of Conferral光电技术研究所
Degree Discipline光学工程
Keyword光腔衰荡 高反射率 宽谱 半导体激光器 自混合 频率选择性光反馈
Abstract高反镜的广泛应用和高反膜性能的不断提高,使高反射率测量的需求日益迫切。现有技术存在成本高、装置复杂、测量精度难以提高等诸多限制。针对这种现状,本文提出了两种新的连续激光光腔衰荡技术,能得到高精度、高可靠性的高反射率测量结果。 本文提出了宽谱连续波光腔衰荡技术用于测量高反射率,推导了宽谱连续波光腔衰荡信号的频域和时域表达式。建立了宽谱连续波光腔衰荡实验装置,采用锁相方式探测光腔输出信号一次谐波的振幅和相位随调制频率的变化曲线,构造同时含有幅频和相频信息的均方差拟合函数,拟合得到光腔衰荡时间。在此基础上,提出了一种连续波复合衰荡光腔技术,用直腔和折叠腔测量相结合的方法,由两种腔型光腔衰荡信号一次谐波的振幅比值和相位差值构造误差函数,通过拟合同时得到直腔衰荡时间和折叠腔衰荡时间,从而同时确定腔镜反射率和待测镜反射率,提高了测量精度。另一方面,提出了时域拟合方法用于分析稳态光腔衰荡信号,与频域探测和拟合方法同时使用,可以提高宽谱连续波光腔衰荡技术的可靠性。 针对脉冲光腔衰荡技术中存在的模式失配问题,提出了基于光束传输矩阵的脉冲光腔衰荡理论,将其用于分析模式失配对光腔衰荡测量的影响。数值模拟结果表明,模式失配情况下对脉冲光腔衰荡信号取对数后采用直线拟合得到的光腔衰荡时间比传统的单指数衰减拟合方法更为准确。 基于半导体激光器的自混合效应,提出了自混合光腔衰荡技术用于测量高反射率,建立了自混合光腔衰荡实验装置,得到了自混合光腔衰荡信号,并利用方波下降沿关闭半导体激光器后实现指数衰减信号探测。实验结果表明,当腔镜反射率大于99.99%时,高反射率测量的重复性精度优于1ppm。通过引入仪器响应函数,采用多参数拟合同时确定衰荡时间和系统响应时间,消除了系统响应时间对高反射率测量的影响。比较了自混合光腔衰荡和宽谱连续波光腔衰荡方法,两种方法对同一样品的测量结果非常一致。在此基础上,通过去除腔镜直接反射回激光器的一次反射光,提出了基于频率选择性光反馈的光腔衰荡技术,使激光功率到衰荡腔的耦合效率始终比较高,而且大大降低了对衰荡腔镜的调节精度要求,提高了测量效率。 基于自混合光腔衰荡和频率选择性光反馈光腔衰荡技术,开展了高反射率测量仪的研制工作。
Other AbstractThe accurate measurement of high reflectivity is very important for the highly reflective (HR) mirrors has been widely used and the performance of the HR coatings has been greatly improved. The currently-used cavity ring-down techniques are costly, complicated and the measurement sensitivity is limited. In this thesis two novel cavity ring-down (CRD) techniques, i.e., the broadband, continuous-wave (cw) CRD technique and the self-mixing CRD technique, are developed for accurate and reliable high reflectivity measurement. The main research contents include: A broadband, cw cavity ring-down technique is developed for the high reflectivity measurement. The theoretical expressions are given in both frequency- and time- domains. The corresponding experimental setup is established. The amplitude and phase shift of the first harmonic of the CRD signal as a function of the modulation frequency are measured by a lock-in method. A mean square variance, including both amplitude and phase shift factors, is minimized to determine the cavity decay time. Further, by calculating the amplitude ratio and phase difference between the linear and folded cavities, a compound CRD method is developed to determine simultaneously the cavity decay time of the linear and folded cavities. Thus the reflectivity of the cavity mirror and the inserted HR mirror are determined simultaneously with a high precision. On the other hand, the steady temporal waveform of the cw-CRD signal is analyzed by a fitting procedure in time domain to determine the cavity decay time. The reliability of the cw-CRD method is enhanced by employing simultaneously the fitting procedures in frequency- and time- domains. A ray-transfer-matrix model for the pulsed-CRD is developed to investigate the influence of the mode mismatching on the high reflectivity measurement. It is indicated by the numerical simulations that the cavity decay time obtained by the linear fitting procedure after calculating the natural logarithmic value of the CRD signal is more accurate than that by the conventional single exponential decay fitting procedure. A novel cavity ring-down technique employing the self-mixing (SM) effect of a semiconductor laser is developed for the high reflectivity measurement. The experimental SM-CRD setup is established and the corresponding exponential decay signal is obtained after shutting down the semiconductor laser by the negative step of the square-wave-modulated signal. It is indicated by the experimental results that the repeatability of the SM-CRD setup is better than 1ppm when the reflectivity of the cavity mirrors is higher than 99.99%. The influence of the instrumental response time on the response time is eliminated by simultaneously determine the cavity decay time and the instrumental response time via a multi-parameter fitting procedure. The reflectivity of the cavity mirror, determined by both SM-CRD and broadband cw-CRD techniques are in excellent agreement. A frequency-selective optical feedback (FOF) based cavity ring-down technique is developed to avoid the direct reflection from the input cavity mirror into the laser cavity so that the laser power can be more frequently coupled into the ring-down cavity than that in the SM-CRD technique. Compared with the SM-CRD technique, the FOF-CRD technique is less sensitive to the obliquity of the cavity mirrors and has a higher measurement-efficiency. A reflectometer based on the SM-CRD/FOF-CRD techniques is developed for the accurate high reflectivity measurement.
Pages133
Language中文
Document Type学位论文
Identifierhttp://ir.ioe.ac.cn/handle/181551/280
Collection光电技术研究所博硕士论文
Recommended Citation
GB/T 7714
龚元. 连续激光光腔衰荡法精确测量高反射率研究[D]. 光电技术研究所. 中国科学院光电技术研究所,2008.
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