基于自外差激光线宽测量方法改进的理论与实验研究.pdf基于自外差激光线宽测量方法改进的理论与实验研究

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详细说明：基于自外差激光线宽测量方法改进的理论与实验研究。本文从自外差线宽测量的基本原理出发，分析了传统LC-RDSHI线宽测量精度有限的根本原因。……致谢致谢又一年春风碎柳,百花碾落,驻足回首,兀自发现流年已悄然逝去。岁月捎走青涩,沉淀下难忘的记忆古语有云:“师者,传道授业解惑者乜”。恩师刘涛研究员是一个学识渊博, 治学严谨的科研工作者,同时也是一个严格而又不失慈爱的学习以及精神导师。在其三年的悉心指导下,我逐渐养成了乐于探索、勤于思考的丬惯。由衷的感谢他对我的教诲,我将铭记于心非常感谢张首刚研究员对量子频标研究室付出的心血,给我们提供了良好的学习科研环境,也时常在生活上给予我们帮助。非常感谢董瑞芳老师、张晓斐老师在论文方面给予的细心指导与莫大帮助, 使我的论文写作水平获得提升。同时也非常感谢量子颎标硏究室的姜海峰老师、常宏老师、阮军老师、杜志静老师、马杰老师、李孝峰老师在学丬上的指导以及生活中的关怀。特别感谢高静师姐、焦东东师兄,闫露露师姐,学习方面不吝解疑,生活中时常给予关心。也十分感谢邓雪师姐、刘杰师兄、陈龙师兄、刘军师兄、张林波师兄、许冠军师兄、藏奇、曹群在学习及生活上的帮助与关心。非常感谢卢晓春、窦忠、李孝辉、郭际、王玉林等中心领导,感谢人事教育处李平处长、张止老师给予的帮助,是你们将我带到了国家授时中心的大舞台, 为我们提供了学习和生活上的各种便利,让我在此快乐的学习生活。十分感谢玊浩奔、白巍凯、项晓和翟艺伟、董彪、樊松涛、施俊如、韩建新、魏雅静、髙喆、赵越、史琛、王明、吴鹏、张旭海、于碧云、饶云峰、张涛姚当等同学的帮助与陪伴。由衷地感谢我的妈妈、哥哥和妹妹以及逝去的父亲,对我无时无刻的关爱与包容,让我变得坚韧与勇敢真诚地感谢我的发小陈根锐、陈绪山、蒋世杰、隆鑫、陈嘉强、李忠班、陈超兴、赖凡、陈群、汤燕,多年来对我的支持与陪伴,真切的感谢张六一,总是对我包容与关心,也真心感谢刘静姐对我的引导与关怀。最后,感谢对本文提出宝贵意见的各位评审专家以及所有关心、支持、帮助过我的老师、同学和朋友们。作者:陈玖朋摘要摘要激光线宽或相干长度是光频传递,光纤传感,精密光谱测量,激光雷达、泱距以及遥感等研究领域的一项重要指标,对这些系统的噪声性能、测量距离、精度和灵敏度等起着决定性作用。因此,对超窄激光线宽进行高精度的测量成为激光器研究领域的一个热点。目前,叮采用的光谱线宽及激光频率噪声特性的测量手段中,自外差探测是一类比较理想的测量方案。自外差探测不需要另一台超窄且更加稳定的光源用作参考,且瀲光的光谱线型可以直接观测到,无需复杂的频率转换技巧,测量结果直接来源于其拍频谱。然而,现有的自外差测量技术方案中,延迟自外差法 (DSHⅠ)测量分辨率极为有限,仅适合线宽不低于1kHz的激光线宽测量;尽管循环损耗补偿延迟自外差法(LC-RDSHⅠ〕解决了DSH测量分辨率较低的不足, 但其测量精度较为有限,且系统调试比较繁杂,不利于实际应用。本文从自外差线宽测量的基本原理出发,分析了传统LC-RDSH线宽测量精度有狠的根本原因。进而提出了参数不敏感型 LC-RDSH以及 Michelson型 LC- RDSHI。相较于传统LC-RDSH,本文提出的两种新方案具有更高的线宽测量精度,且系统调试过程更为简易。根据 LC-RDSH的数学模型,理论推导了两种新方法的输岀拍频功率谱,并结合软件仿真,分析了系统参数变化以及延迟时间对拍频信号功率谱的影响。同时,讨论了LC-RDSH系统的多次循坏干涉效应、相对强度噪声、光纤双折射效应以及频率振动等对激光线宽测量精度的影响在理论分析基础之上,我们搭建了相应的实验装置,测量了三种方法的系统输出功率谱,基于测量的功率谱比较了三种线宽测量方法的测量精度,实验结果表明,相较于传统 LC-RDSHI,参数不敏感型LC- RDSHI以及 Michelson型 LC- RDSHI系统调试更为简易,同时系统输出频谱将多次循环下涉效应引起的下扰信号频谱从待测信号频谱中分离岀去,消除了环路有效増益、耦合器耦合效率等系统参数变化对输岀功牽谱线型的影响,从而具有更高的线宽测量精度。此外, 由于光纤存在双折射效应,传统LC-RDSH与参数不敏感型LC- RDSHI系统偏振态极不稳定,高阶拍频信号频谱的信噪比较低。而 Michelson型LC- RDSHI系统基于 Michelson干涉仪结构并采用法拉第镜以及双向掺铒光纤放大器 ( Bi-EDFA),消除了光纤双折射效应的影响,系统偏振态具有髙稳定性,在测试条件允许的情况下,是最为理想的循环自外差超窄激光线宽测量方案。关键字:;激光线宽测量,自外差法,拍频功率谱,参数不敏感,系统偏振态 Abstract Abstract The linewidth, or the coherence length of a lase is an important indicator, which limits its aplication in the fields of optical frequency transmission, optical fiber sensing, precision spectroscopy, laser radar, range finding or remote sensing,etc. Low-noise performance, measuring distance, accuracy and sensitivity of these systems all depend on it. How to precisely measure the linwidth of the applied laser is always a key issue Currently, self heterodyne detection is the most promising one for the spectral linewidth measurement and laser frequency noise characterization which does not require another ultra-narrow and more stable light source as a reference and the output spectrum of the laser can be observed directly. Meanwhile, the measurement results directly from its RF frequency spectrum without complex frequency conversion. The use of only a single laser for accurate measurement of the extremely narrow laser linewidths is not only today but also in the future However, in the existing self-heterodyne detection techniques, the resolution of delayed self-heterodyne interferometer(DSHI) is extremely limited, which could only be applied to laser linewidth of less than IkHz. Although the conventional loss compensated recirculating way (LC-RDSHI) improved the resolution of the delayed self-heterodyne interferometer. Its measurement accuracy is still constrained and the system adjustment is too hard to be applied in the real case. In order to overcome the deficiencies of the traditional self-heterodyne detection methods, in this paper the delayed self-heterodyne mathematical model is studied to find the causation of the accuracy limitation of the conventional LC-RdShi, based on the basic principles of self-heterodyne detection. Furthmore, the Parameters-Insensitive LC-RDSHI and the Michelson interferometeric LC-RDSHI are proposed. Compare to the previous studies, the output power spectrum is insensitive to system parameters of the two methods improve the overall accuracy as well as an easier application. The software simulations shows the impact of the variation of system parameters and the delay time to the power spectrum profile of the beat notes. In the meantime, the multi-interferences effects of the relative intensity noise. vibration frequency and fiber birefringence of LC-RDshi system are also discussed in this thesis Then an experimental equipment is set up according to the theoretical analysist Abstract to mcasurc thc systcm powcr spcctrum of the thrcc mcthods. Bascd on the mcasurcd power spectrum, the linwidth measurement accuracies of the three methods are compared. Experimental results show that the conventional LC-RDshI is constrained in three aspects: firstly, the conventional LC-RDSHI is more complicated to manipulate because of the complex system parameters regulating. Secondly, the conventional LC-RDSHI shows a strong multi-interference, and a low precision Thirdly, it is sensitive to cnvironment and instruments. Mcanwhilc, rcsults from the Parameters-Insensitive LC-rdshi and michelson interferometric Lc-rdshi show that these two methods enhance the linewidth measurement accuracy since the system parameters variation has a smaller effect on the output power spectrum. However, since the structure of the parameters Insensitive lc-rdshi is the mach-Zehnder interferometeric, the system polarization state is very unstable which needs timely adjustments and the signal to noise ratio of high-orders of beat notes is quite low. In the case that Faraday mirrors and bi-EDFA are available, the Michelson interferometric LC-RDSHi should be the most ellicienl sell-heterodyne detection technique for characterising the ultra-narrow laser linewidth and its frequency noises Key words: laser linewidth measurement, loss compensated recirculating dealyed self-heterodyne interferometer(LC-RDSHI), beat note signal power spectrum Parameters-Insensitive, polarization state of the system 目录目录致谢中·“·:·?鲁于·,·,世于·,计中出量中乎鲁摘要 Abstract 日录图表目录中垂。中中和e着中和 XI 第一章前言. 1.1研究背景. 1.2研究现状.. 4“.4“4““4“日44日4;“4; 1.3论文主要工作及结构第二章激光线宽理论 2.1肖洛一汤斯线宽 2.1.1矢量理论 2.1.2RLC振荡电路模型 22超过肖洛汤斯线宽 56788 22.1K因子展宽…… 222K因子展宽 22.3∝因子展宽 224k因子展宽… 善,善番普。4暑4,4 22.5弛豫振荡………… 10 2.,2.6非均匀展宽…………… 第三章线宽测量技术 13 3.1外差探测.13 3.2光频鉴别器. 3.3自外差探测. 17 33.1延迟自外差法…… +··中····:*···········:"中··"······:·甲 3.3.1.1M-Z型DSHI… .“··.····*···········中··“·4中‘=·中 .19 331.2 Michelson型DSH-… 20 3.3.1.3光纤延时线对DSH的影响 ·”·········中平···中··平·····→··"·········"······ 22 3.3.2循坏损耗补偿延迟自外差法…… ……23 3.3.2.1相对强度噪声 26 3.3,22光纤双折射效应……………………………27 VIL 日录 3.3.2.3频率稳定性的影响 3.32.41f噪声的影响…,,… 第四章两种改进循环自外差法的理论分析. 37 4.1系统参数不敏感型循环延迟自外差法系统输出功率谱. 37 4.1.1系统参数不敏感型循环延迟自外差法拍频信号功率谱仿真 40 4,2 Michelson型干涉仪结构的循环自外差法系统输出功率谱. 41 42. 1 Michelson型循环自外差法拍频信号功率谱仿真及分析…………44 第五章循环损耗补偿延迟自外差法实验 47 51实验系统 47 待测激光器…… n rintrirTnirntT首tt世tttt …48 频移器 48 光纤放大器(EDFA)…… 光电探测器峰自自面曲由 50 5.2系统设计及优化 52.1光功率控制 52 522非线性效应… t主:?主 ……52 523EDFA的附加白噪声…… 53 5.2.4偏振控制-…… .54 52.5环境干扰控制 …54 5.3信号处理及结果分析 54 53.1功率谱测量… ··=···=·=····=·“ 5 5.32NKT激光器线宽测量… …59 53.2.110dB直接测量 59 5322 Voigt拟合……… 62 第六章结论及下步工作 67 6结论 62下步工作 67 参考文献 69 作者简介及在学期间发表的学术论文与研究成果 …73 图表目录图表目录图1.1连续波调频技术(FMCW)原理图图21矢量模型.6 图22洛伦兹线宽仿真图23激光器谐振腔模型原理图.… 图3.1外差探测原理图中事,,B垂垂着B和。垂·。垂··中中。市和.和中,中和中着垂垂图3.2外差探测将信号光谱转换到低频示意图 14 图3.3激光器频率噪声测量原理图图3.4光频鉴别器用于激光线宽测量图3.5自外差探测光场混合示意图图3.6M-Z型DSHL 图3.7 Michelson型DSHI. 20 图38不同延迟时间对应的系统输出光谱线型 22 图3.9传统LC- RDSHI 23 图4.l系统参数不敏感型LC-RDSH 4““4“; 37 图42不同环路有效增益时的仿真频谱. ,得 40 图4.3耦合器不同耦合效率时的仿真频谱. 图44 Michelson型干涉仪结构的循坏自外差线宽测量系统.… 42 图4.5信号光不同循环次数(不同延迟时间)对应的系统输出光谱线型.…45 图46不同系统参数条件下系统输出的光谱线型. 46 图51实验装置原理图.… ……48 图5.2声光调制器衍射效率. 49 图5.3双向掺铒光纤放大器(Bi-EDFA)结构图. ∴419 图5.4光电探测器信噪比曲线. 图5.5光电探测器噪声电压喜暮4喜日丰得 51 图56光电探测器(左:原理图;右:实物图) 图57布里渊阈值与光纤长度的关系 2 ……5 图58120kn实验室单模光纤的受激布里渊散射阈值 53 图59隔音隔振木箱 54 图5.10不同环路有效增益时的系统输出功率谱. 57 图5.11耦合器不同耦合效率时的系统输出功率谱. 59 表5.1LC- RDSHI的线宽测量关系图表目录图512 Michelson型LC-RDSH的前八阶拍频功率谱.…60 图5.13不同延时光纤长度测得的激光线宽值. 图5.14不同环路有效增益测得线宽值. 表52 Voigt拟合获得的洛伦兹及高斯线宽… 63 图5.15 Voigt拟合 64 图5.16不同高斯及洛伦兹线宽的ⅴoigt型

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