【作者】 黄媛媛；

【导师】 刘海荣；

【作者基本信息】 华中科技大学 ， 物理电子学， 2008， 硕士

【摘要】 超连续激光光源能够在很宽的光谱范围内同时产生高重复频率的多波长超短光脉冲,与其他短脉冲光源相比具有谱宽较宽、稳定性较好及宽带相干性的优点,因而被广泛应用于光通信、超短脉冲的产生、光相干层析及光频率测量等领域。由于具有较高的非线性系数和灵活可控的色散特性,高非线性光子晶体光纤已经成为目前用于研究产生超连续谱的重要研究对象。另外由于包层的独特结构,高非线性光子晶体的波导色散对光纤色散的贡献很大,通过光纤结构的合理设计可使其零色散波长移至短波长(670～880nm),利用工作在800nm波段的钛宝石飞秒激光器可在此光纤中产生丰富的非线性现象。光子晶体光纤自问世以来得到了迅速发展,制备工艺不断完善,新型的光纤设计不断出现,目前已广泛应用于光电子学领域的前沿研究。本文对高非线性光子晶体光纤的结构设计,光学传输特性,制备工艺和熔接关键技术进行了系统、深入的研究。主要内容包括:(1)在广泛阅读国内外参考文献的基础上,分析比较现有的光子晶体光纤理论模拟方法,说明选用光束传播法、平面波方法和有限元法分别作为光纤色散、非线性和衰减特性模拟方法的原因。(2)研究高非线性光子晶体光纤的色散、非线性以及衰减特性,详述如何利用Rsoft软件进行光纤结构设计,以及获得光纤的光学传输特性与光纤结构参数的关系,并通过对模拟计算的结果的分析,介绍如何设计一种可利用钛宝石飞秒激光器产生平坦超连续谱的高非线性光子晶体光纤。(3)介绍光子晶体光纤的制备工艺,根据理论设计的光纤结构制备出高非线性光子晶体光纤产品。(4)结合光纤熔接理论,研究高非线性光子晶体光纤熔接关键技术。(5)测试并分析所制备出光纤的光学性能,展望通过光纤结构的优化设计和制备工艺的进一步完善,制备出完全符合商用标准的光纤产品。最后得出的结论:根据理论设计并结合现有的制备工艺和设备,制备出一种零色散点在800nm附近,具有平坦色散的低衰减高非线性光子晶体光纤,利用泵浦波长在800nm波段的钛宝石飞秒激光器在该光纤中得到了展宽超过900nm且较为平坦的超连续谱。更多还原

【Abstract】 Supercontinuum sources have great advantages of broadband radiation, stability and spatially coherent. They are starting to be used in applications such as optical communications, the generation of ultra-short pulse, optical coherence tomography(OCT), optical frequency metrology, and so on. Recent research efforts have been focus on the development of supercontinuum sources using micro-structured fibers. Wide Supercontinuum spectrum has been successfully generated by photonic crystal fiber (PCF) owing to its highly nonlinearity and flexible design of the dispersion profile. In addition, the tailorability of the cladding structure enables high flexibility in the design of the dispersion profile facilitating different nonlinear effect, especially the zero-dispersion wavelength(ZDW) can be shifted into short wavelength band(670-880nm)because of the large waveguide contribution to the dispersion which will be suitable for supercontinuum generation with Ti: sapphire laser pulses.Recently Photonic crystal fiber has attracted of a lot of researchers interests and theoretical analysis and fabrication study have been carried on by a lot of research groups. Nowadays new sorts of fiber are continuously appearing. In this thesis, the methods of structure design, the transmission characteristics, the fabrication process and the key technique in fiber splicing will be discussed. The main parts are as follows:(1) The mathematical methods used in the investigation of photonic crystal fiber are deduced and analyzed. Chapter 2 has introduced the beam propagation method, plane wave method and finite element method respectively. And in Chapter 3 these methods are used to simulate the fiber characteristics with chromatic dispersion, nonlinear coefficient and confinement loss respectively.(2) The relationship between fiber structure parameter and optical transmission characteristics are discussed using Rsoft software. Basing on the theoretic simulation, a highly nonlinear photonic crystal fiber is designed for supercontinuum generation with Ti: sapphire laser pulses.(3) The fabrication process of photonic crystal fiber is introduced. And with the technique mentioned in Chapter 4 the photonic crystal fibers have been fabricated according to the theoretical design. (4) The key technique of photonic crystal fiber splicing with normal single mode fiber is discussed theoretically and experimentally.(5) The characteristics of fiber chromatic dispersion, nonlinear coefficient and confinement loss are measured. The fiber for commercial application is expected by optimizing the fiber structure and fabrication technique.The thesis draws a conclusion that a highly nonlinear photonic crystal fiber is designed and fabricated, of which the zero-dispersion wavelength is around 860nm and the dispersion curve at 800nm wave band is flattened. Supercontinuum emission with spectrum stretching over 900nm is obtained by injecting Ti: sapphire laser pulses.更多还原