多种包层材料亚波长光纤的色散和非线性特性研究

发布时间：2018-02-03 03:58

本文关键词： 亚波长光纤色散曲线非线性系数曲线超连续谱有限元法　出处：《北京交通大学》2017年硕士论文　论文类型：学位论文

【摘要】：近年来,高非线性光纤被广泛应用于超连续谱领域。目前,亚波长光纤作为高非线性光纤的一种,由于具有损耗小、波导色散大、非线性系数高等特点,已成为当前的研究热点之一。本文的研究工作是通过改变亚波长光纤的半径及包层材料来获得平坦变化的正常色散曲线,并以此产生平坦可见波段超连续光谱,具体的工作如下:首先,研究了不同半径的空气包层亚波长光纤的群速度色散特性和非线性特性。主要是通过调整亚波长光纤的半径的方法来进行数值计算。先设置几组纤芯半径间隔为200 nm的亚波长光纤进行数值计算,找出两组相近且处于正常色散区的色散曲线。对于这两组亚波长光纤,设置纤芯半径间隔为50 nm,进一步计算色散曲线。最后得到了一组色散曲线相对平坦的亚波长光纤。其次,研究了不同包层材料的亚波长光纤的群速度色散特性和非线性特性。相对于空气包层,本文选用了水、重水、匹配油三种不同的材料作为亚波长光纤的包层。对于不同包层的亚波长光纤,通过有限元仿真计算,不同半径的亚波长光纤的色散曲线。结果表明,对于水包层亚波长光纤而言,当纤芯半径为800 nm时,可获得777 nm-1685 nm波段内平坦变化的正常色散曲线;对于重水包层而言,当纤芯半径为920nm,可获得593nm-1800nm波段内平坦变化的正常色散曲线;对于匹配油包层而言,当纤芯半径为1150 nm,可获得626 nm-1800nm波段内平坦变化的正常色散曲线。为了提高光纤的非线性系数,提出并且研究了改进的亚波长光纤的色散和非线性特性。最后,通过广义非线性薛定谔方程的数值求解,计算光纤中超短脉冲的演变,其中,当水包层时,当纤芯半径为800nm,获得了波长范围为645nm-1238 nm且平坦性较好的超连续谱,当利用改进的亚波长光纤时,同样的情况下,获得了3dB波长范围415 nm-1355 nm且平坦性较好的超连续光谱。
[Abstract]:In recent years, high nonlinear fiber has been widely used in the field of supercontinuum spectrum. At present, subwavelength fiber as a kind of high nonlinear fiber has the characteristics of low loss, large waveguide dispersion and high nonlinear coefficient. The research work in this paper is to obtain the normal dispersion curve of flat change by changing the radius of subwavelength fiber and cladding material, and to produce the flat visible band hypercontinuum spectrum. The specific work is as follows: first. The group velocity dispersion and nonlinear characteristics of air-cladding sub-wavelength fiber with different radii are studied. The numerical calculation is mainly carried out by adjusting the radius of sub-wavelength fiber. 200. The subwavelength fiber at nm is numerically calculated. The dispersion curves of the two groups are found in the normal dispersion region. For the two groups of sub-wavelength fibers, the core radius interval is set at 50 nm. Finally, a set of subwavelength fibers with relatively flat dispersion curves are obtained. Secondly. The group velocity dispersion and nonlinear characteristics of subwavelength fiber with different cladding materials are studied. Compared with air cladding, water and heavy water are selected in this paper. Three different materials of matching oil are used as the cladding of sub-wavelength fiber. The dispersion curves of subwavelength fiber with different radius are calculated by finite element simulation for the subwavelength fiber with different cladding. The results show that. For water-clad sub-wavelength fiber, when the core radius is 800nm, the normal dispersion curve with flat variation in 777nm band can be obtained. For heavy water cladding, when the core radius is 920nm, the normal dispersion curve with flat variation in 593nm-1800 nm band can be obtained. When the core radius is 1 150 nm, the normal dispersion curve in 626 nm-1800nm band can be obtained. In order to improve the nonlinear coefficient of fiber, the normal dispersion curve can be obtained. The dispersion and nonlinear characteristics of the improved sub-wavelength fiber are proposed and studied. Finally, the evolution of ultrashort pulses in the fiber is calculated by solving the generalized nonlinear Schrodinger equation. When the core radius is 800nm, the wavelength range is 645nm-1238nm and the flatness is better. When the modified sub-wavelength fiber is used, the same condition is obtained. A 3dB wavelength range of 415 nm-1355 nm with good flatness has been obtained.
【学位授予单位】：北京交通大学
【学位级别】：硕士
【学位授予年份】：2017
【分类号】：TN253

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