新型双折射非线性微结构光纤的理论与实验研究

发布时间：2018-05-29 06:28

本文选题：微结构光纤 + 双折射　；参考：《燕山大学》2016年博士论文

【摘要】：双折射和非线性是微结构光纤(MOF)所具有的重要特性,自MOF诞生以来已有大量的文献分别报道了对双折射和非线性特性的研究。本文将MOF的非线性与双折射相结合,通过创新的设计理念探索MOF双折射和非线性的相互关系,并在实验上研究飞秒激光脉冲在双折射和双零色散MOF中产生非线性的作用过程。本文的研究内容主要包括以下几个方面。首先通过求解非线性薛定谔传输方程数值模拟了飞秒激光脉冲在设计的高非线性MOF中的传输,根据模拟结果分析了飞秒激光的脉冲峰值功率,脉冲宽度,脉冲波长及初始啁啾对在光纤中产生的超连续谱的影响。其次,论文设计了正八边形包层椭圆形纤芯结构的MOF,模拟分析了包层空气孔直径和纤芯长短轴之比对MOF双折射和非线性带来的影响。由模拟分析结果可知,这种光纤包层的对称性较高,MOF的双折射主要是由纤芯的不对称造成的。论文又提出了中心大孔的压缩八边形和类矩形纤芯结构两种MOF,并分析了孔径、孔间距和纤芯长短轴之比对双折射、非线性和色散带来的影响,得到了减小孔间距能更有效地提高MOF双折射和非线性以及输出脉冲的宽度随纤芯的长短轴之比增大而增大的结论。再次,采用有限元法对课题组自行研制的一种新颖的V型结构的MOF的各项参数进行理论模拟,发现它的非线性和双折射都较高;通过对飞秒激光脉冲在其中传输的实验结果,分析了V型MOF的色散、双折射、入射光的功率、入射光的中心波长对产生的超连续谱造成的影响。然后,通过对课题组自行拉制的一种包层无序排列的双折射非线性MOF进行飞秒激光传输实验,首次发现入射脉冲的中心波长位于MOF的正常色散区也可以产生显著的斯托克斯波和反斯托克斯波,并用四波混频的相位匹配理论解释了两种波的产生。进一步研究发现通过相位匹配条件、入射脉冲偏振化方向、平均功率及中心波长的调节可以有效地控制双折射非线性MOF中两种波的强度、中心位置及转化效率。最后,通过计算,得到了MOF截面结构参数对产生的两个零色散波长位置的影响规律;分析得到了单零色散和双零色散MOF的色散和四波混频相位匹配之间的关系;并在具有双零色散的MOF中进行光谱传输实验,验证了MOF的零色散个数及位置对产生的四波混频波长转换的影响规律。
[Abstract]:Birefringence and nonlinearity are important characteristics of microstructured optical fiber (MOF). Since the birth of MOF, the study of birefringence and nonlinear characteristics has been reported in a large number of literatures. In this paper, the nonlinear and birefringence of MOF are combined, the relationship between birefringence and nonlinearity of MOF is explored by innovative design idea, and the nonlinear process of femtosecond laser pulse in birefringence and double zero dispersion MOF is studied experimentally. The research content of this paper mainly includes the following aspects. The propagation of femtosecond laser pulses in a high nonlinear MOF is numerically simulated by solving the nonlinear Schrodinger propagation equation. The peak power and width of femtosecond laser pulses are analyzed according to the simulation results. The influence of pulse wavelength and initial chirp on the supercontinuum spectrum in fiber. Secondly, the paper designs the oval core structure of octagonal cladding, and simulates and analyzes the influence of MOF birefringence and nonlinearity caused by the ratio of the air hole diameter and the long and short axis of the cladding. The simulation results show that the high symmetry of the fiber cladding and the birefringence of MOF are mainly caused by the asymmetry of the core. In this paper, two kinds of MOFs, compression octagonal structure and rectangular fiber core structure, are proposed, and the effects of aperture, hole spacing and ratio of the long and short axis of the core on birefringence, nonlinearity and dispersion are analyzed. It is concluded that decreasing the hole spacing can increase the MOF birefringence and nonlinearity more effectively, and that the output pulse width increases with the increase of the ratio of the long and short axis of the core. Thirdly, the parameters of a novel V-shaped structure MOF developed by our team are theoretically simulated by the finite element method, and it is found that the nonlinear and birefringence of the MOF are both high, and the experimental results of femtosecond laser pulse transmission in the system are given. The influence of dispersion, birefringence, power of incident light and central wavelength of incident light on the supercontinuum spectrum of V-type MOF is analyzed. Then, femtosecond laser propagation experiments were carried out on a kind of birefringent nonlinear MOF with random arrangement of cladding, which was made by our group. It is found for the first time that the central wavelength of the incident pulse is located in the normal dispersion region of MOF and can also produce significant Stokes and anti-Stokes waves. The generation of the two waves is explained by the phase matching theory of four-wave mixing. It is further found that the intensity, center position and conversion efficiency of the two waves in birefringent nonlinear MOF can be effectively controlled by adjusting the polarization direction, average power and central wavelength of the incident pulse under the phase matching condition. Finally, the influence of the structure parameters of MOF section on the positions of the two zero dispersion wavelengths is obtained, and the relationship between the dispersion of MOF with single zero dispersion and double zero dispersion and the phase matching of four wave mixing is obtained. Spectral transmission experiments were carried out in MOF with double zero dispersion to verify the influence of zero dispersion number and position of MOF on wavelength conversion of four-wave mixing.
【学位授予单位】：燕山大学
【学位级别】：博士
【学位授予年份】：2016
【分类号】：TN253

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