【作者】 陈超；

【导师】 陈鹤鸣；

【作者基本信息】 南京邮电大学 ， 光学工程， 2012， 硕士

【摘要】 随着光纤技术的发展,光纤的传输波段从2μm以下的近红外区域逐渐向更长的中红外甚至远红外区域发展。与普通光纤不同,红外光纤主要用于激光能量的传输。近几十年来,人们在红外光纤领域展开了大量的理论研究工作,并逐渐开始实用化。目前,红外光纤在医学及工业上的CO₂激光能量传输和传感等领域已得到广泛应用。本文通过比较分析材料的光学物理等特性,利用平面波展开法（PWM）对材料带隙进行计算,为了获得一种适合于传输10.6μmCO₂激光的Bragg光纤,选取了适合于传输10.6μmCO₂激光的包层材料（ As 2Se3/PEI ）并确定了其填充率（ fμ0.8）。然后采用基于全矢量有限元法（FEM）的COMSOL软件进行仿真,对红外空心Bragg光纤的结构参数进行优化,当结构参数为:纤芯内径为1 50μm,晶格周期为7μm,高低折射率材料厚度分别为1.4μm和5 .6μm,包层周期达到20层时,实现了其在10.6μm处的低损耗传输,损耗可降低到5. 14dB/km,远远优于目前已达到的10 dB /km以下。考虑到制作工艺的不完善性,本文分析了在包层中引入单个周期缺陷时对其损耗造成的影响。仿真结果表明,在利用第二带隙导光且完整结构晶格周期为μμ7μm的Bragg光纤中,引入尺寸略大于晶格周期的缺陷有助于减小其在10 .6μm波长处的损耗,反之则会使得损耗变大,而且缺陷越靠近纤芯影响越大。在靠近纤芯的第一层引入μ’μ7.18μm的缺陷对降低光纤损耗效果最明显。研究结果对于红外光纤的制作和应用具有重要意义。更多还原

【Abstract】 With the development of optical fiber technology, the transmission wavebands gradually become farther and longer, shifting from near-infrared region below 2μm to mid-infrared even far-infrared. Unlike ordinary optical fiber for signal transmission, infrared Bragg fiber is always using transferring laser energy. Recent decades, we have launched a large number of theoretical studies in the field of infrared fiber, and gradually turned into the practical applications.At present, it has already been widely used transferring the CO₂ laser energy in medicine and industry, and sensor applications.In this paper, by comparing the material’s optical and physical characteristics, and using the plane wave expansion method （PWM） to calculate the band gap, we select suitable materials （ As 2Se3/PEI ） and fill rate （ fμ0.8） in order to get a kinf of Bragg fiber for transmission 10 .6μm CO₂ laser energy. On this basis, combined with the full vector finite element method （FEM） and using COMSOL software simulation to optimize structural parameters of the hollow-core Bragg fiber, and ultimately achieve low-loss transmission of 10.6 laser energy. The specific parameters are as follows, the periodic lattice is 7μm, high and low refractive index material thickness are respectively 1. 4μm and 5 .6μm,together 20 cycles, the radius of the hollow-core is 150μm .The loss value can be reduced to 5. 14dB/km at 10.6μm ,far better than the current 0. 01dB/m.Taking into account the imperfections of the production process, the paper also analyzes the impact of the single cycle defect. Simulation results show that, when the complete structure of the periodic lattice is 7μm in the second band gap , defect which size slightly larger than the periodic lattice can help to reduce the loss of Bragg fiber at 10 .6μm. On the contrary, the loss becomes greater. That is,when the defect 7. 18μm appearing in the first layer near the hollow-core,it is best for reducing the loss. The results have great significance to the production and applications of infrared fiber.更多还原