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题名	大模场双包层光纤光栅的刻写与特性研究
作者	刘刚
学位类别	硕士
答辩日期	2012
授予单位	中国科学院上海光学精密机械研究所
导师	蔡海文
关键词	大模场双包层光纤光栅 相位掩模法 耦合系数 模式特性
其他题名	Study on Inscription and Characterization of Large-Mode-Area Double Clad Fiber Bragg Grating
中文摘要	大模场双包层光纤自从1988年由Sintzer等人提出以来，由于其出色的传输光的能力和包层泵浦技术的应用，在高功率光纤激光器方面发挥着极大的优势。双包层光纤由于具有较大的芯径，可以有效降低传输高功率激光时在纤芯中引起的非线性效应，成为了发展高功率光纤激光器的重要途径之一。在双包层光纤上刻写光栅形成激光器腔镜，则可以避免光纤激光器的端面熔接耦合，大大降低插入损耗，并易于与其它光纤器件连接，可实现更大功率的激光输出。光纤光栅作为一种低损耗器件，具有非常好的波长选择特性，采用光纤光栅做谐振腔大大简化了激光器的结构同时提高了激光器的信噪比和可靠性，有利于获得窄线宽、高光束质量的光纤激光器。光纤光栅以其使用灵活、成本较低、易于选频等优点，成为全光纤化高功率激光器首选谐振腔。 本文围绕大模场双包层光纤光栅的刻写及特性展开了一系列的理论与实验研究，所涉及到的具体内容如下： （1）搭建了准分子激光器相位掩模法刻写双包层光纤光栅的实验装置，在载氢增敏的Nufern LMA-DCF-20/400光纤上实现了光纤布拉格光栅的刻写，采用模式匹配器法对光栅的谱线进行了在线测试，研究了光栅的布拉格波长随曝光时间的变化关系，并利用切趾幅度模板改变光栅区空间曝光量的方法得到了中心波长为1081.44nm，反射谱线对比度大于18.6dB的切趾双包层光纤光栅。 （2）在课题组前期研究成果的基础之上，分别从耦合模理论和多层膜理论详细研究了纤芯偏移量对单模激发场与光栅中LP01、LP11、及更高阶模式的耦合系数及反射光谱的影响，并通过调整架对接单模光纤和双包层光纤光栅的方法 实验研究了纤芯偏移量对光栅反射谱的影响，并用CCD观测到了不同偏移量下的模场光斑分布。同时，文中还就双包层光纤光栅的中心波长随温度的变化特性做了详细的实验研究。 （3）文中除了双包层光纤光栅的刻写及特性研究外，还简要介绍了飞秒激光逐点刻写光纤光栅进行的一些研究工作，搭建了飞秒激光逐点刻写光纤光栅的实验装置，在载氢的SMF-28光纤上写入了周期为500μm、占空比为1:1、谐振波长在1532nm和1557nm、透射谱深度约10dB的长周期光纤光栅，并对栅区进行了显微成像。
英文摘要	Since large-mode-area double clad fiber was first launched by Sintzer in 1988, it has showed great advantages in the high power fiber laser, duo to excellent optical transmission capability and the application of cladding-pumped technology. Double clad fiber can effectively reduce the nonlinear effect in the core of fiber when transmitting high power laser because of its larger core diameter, which makes it one of the important ways to develop high power fiber laser. Inscribing fiber grating in the double clad fiber can avoid splice coupling and lower the insertion loss, it is very convenient to connect with other fiber components and can achieve higher power laser output. Fiber grating as a lower-loss component, it has superior wavelength-selecting properties. Using the fiber grating as the resonant cavity can greatly simplify the structures of laser and improve SNR and stability, also achieve narrow-line width, high beam quality fiber laser. Fiber grating has become the preferred resonant cavity of high power fiber laser, due to its flexible use, low cost and easy frequency-selecting ability. This paper is mainly centered on the study of inscription and characteristics of double clad fiber grating, the detailed contents involved are as follows: (1) The inscription set up for double clad fiber grating is built, fiber Bragg grating (FBG) is then inscribed in the hydrogen-loaded LMA-DCF-20/400 fiber by an excimer laser and phase mask method, its spectrum is measured by mode-field-adaptor method, the relationship between Bragg wavelength and exposure time is carefully studied. Besides, an apodized FBG, centered at 1081.44nm, reflection spectrum more than 18.6 dB, is obtained by changing the spatial exposure dosage of grating area using a pair of apodized amplitude masks. (2) The influence of SMF shift distances on the coupling coefficient between the SMF exciting field and LP01, LP11, or other higher-order modes within the double clad FBG is carefully analyzed; the grating spectrum under different SMF shift distances is also carefully investigated from coupled mode theory and multi-layer theory respectively. Correspondingly, the grating reflection spectrum and corresponding light spots under different shift distances are observed in the experiment. Besides, the temperature properties of FBG’s central wavelength are investigated experimentally. (3) Except for study on inscription and characterization of double clad fiber grating, the inscription of fiber grating by femtosecond laser and point-by-point method is briefly introduced. The inscription set up is built, and a long period fiber grating (LPFG) is successfully inscribed in the hydrogen-loaded SMF fiber with period 500μm, duty cycle 1:1, resonant wavelengths at 1532nm and 1557nm respectively, transmission spectrum depth about 10dB, also the structure of grating is observed by a microscope.
语种	中文
内容类型	学位论文
源URL	[http://ir.siom.ac.cn/handle/181231/16734]
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	刘刚. 大模场双包层光纤光栅的刻写与特性研究[D]. 中国科学院上海光学精密机械研究所. 2012.

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