用于超连续谱产生的七芯光子晶体光纤的研究
发布时间：2019-02-24 11:16
【摘要】：光子晶体光纤的出现为非线性光学领域、高功率光纤激光器以及光纤通信等领域的发展提供了崭新的的平台。在非线性光学领域中,多芯光子晶体光纤可以克服单芯光子晶体光纤模场直径以及热效应等问题,为超连续谱的产生提供了新的思路。本论文以七芯光子晶体光纤为例,一方面针对七芯光子晶体光纤的耦合特性、色散特性以及非线性特性进行理论研究;另一方面,基于设计得到的一种新型的七芯光子晶体光纤,通过数值模拟对超连续谱的产生进行研究,取得的成果主要包括以下几个方面:1.基于多芯耦合模理论推导得到七芯光子晶体光纤的耦合长度,通过全矢量有限元法分析光子晶体光纤结构参数对耦合特性的影响规律;并采用光束传播法动态模拟纤芯之间的能量耦合过程。比较全矢量有限元法和光束传播法得到的耦合长度,结果具有很好的一致性,为合理设计基于七芯光子晶体光纤的结构设计和特性分析提供理论基础。2.提出一种新型的七芯光子晶体光纤结构。利用全矢量有限元方法对七芯光子晶体光纤的色散特性和非线性系数进行了详细的分析,结果表明,通过改变光子晶体光纤包层空气孔间距和空气孔直径,可以有效地调节光纤非线性的大小以及光纤色散曲线的变化;并进一步针对光纤中的同相超模进行模式整形,得到在1.55μm波长处,光纤的非线性系数为68W-1Km-1,损耗为4.576×10-6dB/m,且在计算波段范围内都处于正常色散下的光纤结构。3.利用分布傅里叶方法数值模拟了超短脉冲的展宽过程,进而研究了光纤长度、泵浦波长,脉冲功率和脉宽对光谱展宽的影响。数值仿真结果表明,通过选择合适的脉冲参数可以有效的调节产生的超连续谱的特性。基于本文所设计的七芯光子晶体光纤,当光纤长度L=5cm,初始脉宽T0=50fs,中心波长为1.55μm,脉冲峰值功率为40kw-80kw时,得到展宽约为1101-1331nm的超连续谱,充分显示了具有正常色散的七芯光子晶体光纤在产生高平坦、宽带宽的超连续谱方面的应用潜力。
[Abstract]:The appearance of photonic crystal fiber provides a new platform for the development of nonlinear optics, high power fiber lasers and optical fiber communication. In the field of nonlinear optics, multi-core photonic crystal fiber can overcome the problems of mode diameter and thermal effect of single-core photonic crystal fiber, which provides a new idea for the generation of supercontinuum spectrum. In this paper, we take the seven-core photonic crystal fiber as an example. On the one hand, the coupling characteristics, dispersion characteristics and nonlinear characteristics of the seven-core photonic crystal fiber are studied theoretically. On the other hand, based on the design of a new seven-core photonic crystal fiber, the generation of supercontinuum spectrum is studied by numerical simulation. The main achievements are as follows: 1. Based on the multi-core coupling mode theory, the coupling length of the seven-core photonic crystal fiber is derived, and the influence of the structure parameters of the photonic crystal fiber on the coupling characteristics is analyzed by the full-vector finite element method. The beam propagation method is used to simulate the energy coupling process between the fiber cores. Compared with the coupling length obtained by the full vector finite element method and the beam propagation method, the results are in good agreement, which provides a theoretical basis for the reasonable design of the structure and characteristic analysis of the seven-core photonic crystal fiber. A novel seven-core photonic crystal fiber structure is proposed. The dispersion characteristics and nonlinear coefficient of seven core photonic crystal fiber are analyzed in detail by using full vector finite element method. The results show that by changing the air hole spacing and air hole diameter of photonic crystal fiber cladding, The nonlinearity of fiber and the variation of fiber dispersion curve can be adjusted effectively. Furthermore, the mode shaping of the in-phase supermode in the fiber is carried out. The nonlinear coefficient of the fiber is 68W-1Km-1 at the wavelength of 1.55 渭 m and the loss is 4.576 脳 10 ~ (-6) dB / m. And the fiber structure with normal dispersion in the calculated band range. 3. 3. The effects of fiber length, pump wavelength, pulse power and pulse width on the broadening of ultrashort pulses are numerically simulated by using the distributed Fourier method. The numerical simulation results show that the characteristics of the supercontinuum spectrum can be adjusted effectively by selecting appropriate pulse parameters. Based on the seven core photonic crystal fiber designed in this paper, when the length of the fiber is 5 cm, the initial pulse width is T 0N 50 fs, the center wavelength is 1.55 渭 m, and the peak power of the pulse is 40kw-80kw, the supercontinuum spectrum about 1101-1331nm is obtained. The application potential of the seven-core photonic crystal fiber with normal dispersion in producing high flat and wide broadband supercontinuum spectrum is fully demonstrated.
【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
[Abstract]:The appearance of photonic crystal fiber provides a new platform for the development of nonlinear optics, high power fiber lasers and optical fiber communication. In the field of nonlinear optics, multi-core photonic crystal fiber can overcome the problems of mode diameter and thermal effect of single-core photonic crystal fiber, which provides a new idea for the generation of supercontinuum spectrum. In this paper, we take the seven-core photonic crystal fiber as an example. On the one hand, the coupling characteristics, dispersion characteristics and nonlinear characteristics of the seven-core photonic crystal fiber are studied theoretically. On the other hand, based on the design of a new seven-core photonic crystal fiber, the generation of supercontinuum spectrum is studied by numerical simulation. The main achievements are as follows: 1. Based on the multi-core coupling mode theory, the coupling length of the seven-core photonic crystal fiber is derived, and the influence of the structure parameters of the photonic crystal fiber on the coupling characteristics is analyzed by the full-vector finite element method. The beam propagation method is used to simulate the energy coupling process between the fiber cores. Compared with the coupling length obtained by the full vector finite element method and the beam propagation method, the results are in good agreement, which provides a theoretical basis for the reasonable design of the structure and characteristic analysis of the seven-core photonic crystal fiber. A novel seven-core photonic crystal fiber structure is proposed. The dispersion characteristics and nonlinear coefficient of seven core photonic crystal fiber are analyzed in detail by using full vector finite element method. The results show that by changing the air hole spacing and air hole diameter of photonic crystal fiber cladding, The nonlinearity of fiber and the variation of fiber dispersion curve can be adjusted effectively. Furthermore, the mode shaping of the in-phase supermode in the fiber is carried out. The nonlinear coefficient of the fiber is 68W-1Km-1 at the wavelength of 1.55 渭 m and the loss is 4.576 脳 10 ~ (-6) dB / m. And the fiber structure with normal dispersion in the calculated band range. 3. 3. The effects of fiber length, pump wavelength, pulse power and pulse width on the broadening of ultrashort pulses are numerically simulated by using the distributed Fourier method. The numerical simulation results show that the characteristics of the supercontinuum spectrum can be adjusted effectively by selecting appropriate pulse parameters. Based on the seven core photonic crystal fiber designed in this paper, when the length of the fiber is 5 cm, the initial pulse width is T 0N 50 fs, the center wavelength is 1.55 渭 m, and the peak power of the pulse is 40kw-80kw, the supercontinuum spectrum about 1101-1331nm is obtained. The application potential of the seven-core photonic crystal fiber with normal dispersion in producing high flat and wide broadband supercontinuum spectrum is fully demonstrated.
【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
【参考文献】
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