【作者】 靳爱军；

【导师】 姜宗福； 王泽锋；

【作者基本信息】 国防科学技术大学 ， 光学工程， 2011， 硕士

【摘要】 光子晶体光纤中产生的超连续谱在光谱学、脉冲压缩、可调谐超快飞秒激光源的设计等领域有着重要的应用价值,在近十年得到广泛深入的研究。相干性是超连续谱光源的重要物理特性,本文对其进行了理论和实验研究。首先概述了超连续谱光源的发展历史与研究现状,以及国内外对其相干性的研究进展情况。详细介绍了光子晶体光纤中超连续谱产生的理论基础以及数值仿真模型,分析了色散与非线性效应在超连续谱产生过程中的重要作用。数值模拟了光子晶体光纤中超连续谱的产生。色散是超连续谱产生过程中的一个重要参数,本文对光纤色散的测量方法进行了比较,介绍了干涉法测量光纤色散的原理。搭建了基于超连续谱光源的宽带光纤色散测量平台,对已有的光子晶体光纤色散测量装置进行了改进,提高了其测量精度与自动化程度。测量了两种特殊光纤:全固态光子带隙光纤与氟化物ZBLAN光纤的色散。实验结果与数值计算结果非常吻合,验证了色散测量系统的有效性。对超连续谱光源的相干性进行了阐述,说明了其与普通白光光源相干性之间的区别。在广义非线性薛定谔方程中加入噪声项对超连续谱光源的相干性进行仿真,引入互相干度的概念对其进行量化分析。数值计算了不同泵浦条件下产生的超连续谱光源的相干性,结果表明调制不稳定性是造成超连续谱光源相干性下降的主要影响因素;为了获得高相干的宽带超连续谱,需要在光纤的反常色散区远离零色散波长处使用短脉冲进行泵浦。引入自相干度的概念对长脉冲产生的超连续谱光源的相干性进行了定量分析,搭建了高精度的马赫-曾德尔干涉仪实验系统,对光子晶体光纤中产生的超连续谱光源的相干长度以及自相干度进行了测量。结果表明,整个超连续谱波段内相干性都较好,平均自相干度为0.461;不同波长处的相干长度不同,自相干度也不同,泵浦脉冲中心波长长波一侧相干长度较长,相干性较好。更多还原

【Abstract】 Supercontinuum (SC) generated in photonic crystal fibers (PCFs) has many applications in various fields such as spectroscopy, pulse compression and tunable ultrafast femtoseconds laser sources. In the recent decade, it has been researched widely and deeply. Coherence property is an important physical characteristic of SC source and this dissertation analyzes it theoretically and experimentally.Firstly, the historical development and research state of SC generation are summarized and also the research of coherence of SC is concluded. The theoretical foundation and numerical model of SC generation in PCFs are described, and the role of dispersion and nonlinear effects in the process of SC generation is analyzed. The SC generation in PCFs is numerically simulated.Secondly, because of the importance of the dispersion in the SC generation, its measurement methods are compared and the theory of interference method is illustrated. Broadband dispersion measurement apparatus based on supercontinuum was constructed. The existing apparatus which was used to measure the dispersion of PCFs has been improved with high measurement precision and automation. The dispersion characteristics of two kinds of special fibers all solid photonic bandgap fiber and fluoride ZBLAN fiber are measured. The experimental results match well with the calculation results; as a result, the validity of the dispersion measurement system is clarified.Thirdly, coherence characteristics of SC source are illustrated to distinguish the distinction between the coherence of the conventional white light and SC source. Adding noise in the generalized nonlinear Schr?dinger equation (GNLSE) models the coherence of SC. Degree of mutual coherence is introduced to quantify the coherence of SC. The coherence properties of SC generated under various pump conditions are calculated; from the results, modulation instability is the main effect to degrade the coherence of SC. To obtain coherent broadband SC, the PCF need to be pumped by short pulses which are far from zero dispersion wavelength in anomalous dispersion region.Finally, degree of self-coherence is introduced to quantify the coherence of SC generated by long pulse. High precision Mach-Zehnder interferometer is built to measure the coherence length and degree of self-coherence of SC generated in PCFs. The results show that above the whole SC spectral range the coherence is comparatively good, and the average self-coherence degree is 0.461. The coherence lengths and degree of self-coherence of different wavelengths are different. The coherence length of the longer side of the pump wavelength is better and it presents better coherent property.更多还原