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chi20181227上海光机所廖梅松557447Supercontinuum refers to the process of generating a large number of spectral components by launching high power pump pulse into nonlinear medium. The nonlinear effects include self-phase modulation, four-wave mixing etc. Supercontinuum source can be used for multi-wavelength light source for dense wavelength-division multiplexing communications, used for optical coherence tomography related with medical imaging, used for pulse compression of ultrashort femtosecond laser source, and used for optical frequency measurement metrology. This dissertation focuses on the nonlinear effects and supercontinuum generation in optical fibers. This paper includes seven chapters in total. The first chapter introduces the research progress and application of supercontinuum briefly. The second chapter introduces the technical foundation of supercontinuum generation. The third to sixth chapters are the main research contents of this dissertation. Chapter 7 is a summary and outlook. The first chapter is an introduction, briefly introduces the photonic crystal fiber, and introduces the research progress of supercontinuum, including supercontinuum generation in different fibers with different materials, supercontinuum generation under different pump conditions, and supercontinuum generation in new kind of fibers, such as composite fiber, multi-core fibers, and nanowires. In the second chapter, the nonlinear Schr?dinger equation and its solution method are briefly introduced. The dispersion effects and nonlinear effects of the fiber, such as self-phase modulation, four-wave mixing and Raman effect, are discussed in detail. In the third chapter, we investigate supercontinuum generation by dual-wavelength pumping in photonic crystal fiber with two zero dispersion wavelengths. The supercontinuum generation in the photonic crystal fiber with two zero dispersion wavelengths which are far away from each other is studied systematically. Two pump pulses located in the anomalous dispersion region of the fiber are injected in the photonic crystal fiber to generate supercontinuum. Keeping the peak power of the pump pulse unchanged, increasing the pulse width can enhance the interaction between the two pump pulses, which is advantage for enlarging supercontinuum further. By analyzing the dual-wavelength pumping and the 800 nm, 1950 nm single-wavelength pumping, the potential mechanism of supercontinuum generation was domenstated and the interaction between the two pump pulses was confirmed. In the case of dual-wavelength pumping, the cross-phase modulation between the two incident pulses leads to the blueshift of the short wavelength edge of supercontinuum. The introduction of pulses in the infrared band is benefit for the expansion of the short wavelength boundary of the supercontinuum, while the infrared wavelength boundary remains unchanged. Combining dual-wavelength pumping and photonic crystal fiber with two zero dispersion wavelength can broaden the supercontinuum greatly. Finally, an ultra-wide supercontinuum with 20 dB spectral width from 426 to 2954 nm was obtained. In the fourth chapter, systematic theoretical and experimental studies of soliton self-frequency shift with picosecond pump pulse in tellurite fibers are performed. The mechanism of this phenomenon is explained. When the pump wavelength is 1958 nm and the peak pump power is 250 W, the higher dispersion value at 1958 nm makes the self-phase modulation and the dispersion effect reach a balance, and the soliton self-frequency shift phenomenon occurs. The influence of input parameters on this phenomenon was studied. As the pump pulse power increases, both the number of soliton and the amount of soliton frequency shift increase. As the pump power further increase, the saturation of the Raman effect weakens the soliton self-frequency shift effect. When the pulse width is 2.7 ps, the pulse width of the red-shifted soliton is about 40 fs and the pulse compression factor is about 38. Simulation results can be verified experimentally. The soliton wavelength was shifted from 1990 nm to 2264 nm with the changement of pump power. The maximum displacement was about 274 nm. Soliton wavelengths with different fiber lengths were measured. As the fiber length increases, the soliton wavelength becomes longer and reaches saturation at about 40 cm fiber length. Stable wavelength-tunable femtosecond pulses generated by the phenomenon of soliton self-frequency shift can be used to make tunable mid-infrared lasers for use in medicine or other fields. Chapter 5 studies the generation of mid-infrared supercontinuum in silica photonic crystal fibers. A variety of photonic crystal fibers with the same kind of end face structure have been carefully designed. The six ring air holes on the end face of the fiber can be divided into two groups. The inner three circles mainly affect the fiber dispersion, and the outer three circles mainly affect the fiber loss. Ultrashort pulses (picoseconds and femtoseconds) with wavelengths of 1550 nm and 1950 nm were used as pump pulses to pump the fiber. Under the 1550 nm pump pulse, the main mechanism for extending the supercontinuum to the long wavelength band is the soliton self-frequency shift effect. Whether using picosecond pump pulses or femtosecond pulses, supercontinuum is limited within 3000 nm. The use of fiber with zero dispersion wavelength far from the pump pulse is benefit for the energy distribution in the long wavelength band of the supercontinuum. Under the 1950 nm pump pulse, the effective mechanism for extending the supercontinuum to long wavelength band is the generation of redshifted dispersion waves. With femtosecond pump pulse, the long-wavelength edge of the supercontinuum in PCF c with a negative dispersion slope near the pump pulse exceeds 3 μm. Chapter 6 systematically studies the generation of visible dispersive waves in suspended fiber with different fiber characteristics. Through numerical simulation, the dispersion wave generation under different pump pulse widths and different average pump powers was studied. When the pump wavelength is in the anomalous dispersion region of the fiber, isolated dispersion waves are generated. As the pulse width and pump power increase, the coherence of the dispersion wave remains nearly the same (~1). The process of supercontinuum generation is analyzed in detail. The energy exchange occurs mainly when the first order soliton shrinks. Low soliton order is benefit for high conversion efficiency. Numerical simulations using experimental parameters show that gratings can compress the dispersion wave to about 40 fs. In the experiment, under the pump pulse with a pulse width of 50 fs and a wavelength of 1 μm, the isolated dispersive wave generated in the SCF1 with the large core is around 480 nm due to the cross-phase modulation effect. The isolated dispersive waves generated in SCF2 with small core are around 466 nm and 485 nm, respectively. The full width at half maximum of the dispersive wave in SCF2 is about 40 nm, and the conversion efficiency is about 10%. By comparing the pulse sequence, the coherence of the dispersive wave is better than that of the infrared part. The generation of dispersion waves at low pump power is susceptible to OH loss. Chapter 7 is a summary and outlook.2019atalunwen21912718188916Supercontinuum Generation;Nonlinear Effect;Photonic Crystal FibersResearch on the technology of supercontinuum based on microstructured fiber基于微结构光纤的超连续谱技术研究超连续谱是指强脉冲入射到非线性介质中,通过非线性作用,如自相位调制,四波混频等,产生大量光谱成分的过程。超连续谱可以用于密集波分复用通信的多波长光源,可以用于医学成像技术的光学相干断层扫描,可以用于超短飞秒激光源的脉冲压缩,可以用于测量光频率的光学频率计量学。 本论文重点研究光纤中的非线性效应与超连续谱的产生。本论文总共包括七章。第一章是绪论,介绍超连续谱的研究进展及应用。第二章介绍超连续谱产生的技术基础。第三到第六章是本文的主要研究内容。第七章是总结和展望。 第一章是绪论,简要介绍了微结构光纤,并介绍了超连续谱的研究进展,包括不同材料的光纤中、不同泵浦条件下超连续谱的产生以及新型光纤,例如复合光纤、多芯光纤、纳米线中超连续谱的产生。 第二章简要介绍了非线性薛定谔方程及其解法,并详细阐述了与超连续谱产生密切相关的光纤的色散效应和非线性效应,例如自相位调制、四波混频、拉曼效应等。 第三章提出了双波长泵浦双零色散光子晶体光纤产生超连续谱的方案。系统研究了有两个相距较远的零色散点的光子晶体光纤中超连续谱的产生。两个位于光纤反常色散区的泵浦脉冲入射到光子晶体光纤中产生超连续谱。保持泵浦脉冲峰值功率不变,增加脉冲宽度可以增强两个传输脉冲之间的相互作用,有利于进一步扩展超连续谱的谱宽。通过分析双波长泵浦和800 nm,1950 nm单波长泵浦,阐明了超连续谱产生的潜在机制,证实了两个传输脉冲之间存在相互作用。双波长泵浦情况下,由于两个入射脉冲之间的交叉相位调制作用,会导致超连续谱短波波段进一步蓝移。在红外波段引入脉冲有利于扩展超连续谱的短波边界,而红外边界保持不变。结合双波长泵浦和有两个零色散点的光子晶体光纤可以大大拓宽超连续谱的谱宽。最终,获得了20 dB谱宽从426到2954 nm的超宽超连续谱。 第四章对皮秒脉冲泵浦下碲酸盐光纤中的孤子自频移效应进行了系统的理论和实验研究,并对这一现象的产生机制进行了解释。当泵浦波长1958 nm,峰值功率250 W时,1958 nm处较高的色散值,使得自相位调制和色散效应之间达到平衡,产生了孤子自频移现象。研究了输入参数对这一现象的影响。随着泵浦脉冲功率的增加,孤子数和孤子位移量都增加。随着泵浦功率的进一步增加,拉曼效应的饱和减弱了孤子自频移效应。当脉冲宽度为2.7 ps时,红移的孤子的脉冲宽度约40 fs,脉冲压缩因子约为38。可以通过实验验证仿真结果。改变平均泵浦功率,孤子波长从1990 nm到2264 nm移动,最大位移量约274 nm。测量了不同光纤长度中的孤子波长。随光纤长度的增加,孤子波长变长,在光纤长度约40 cm时达到饱和。通过孤子自频移现象产生的稳定的波长可调谐的飞秒脉冲能够用来制作可调谐的中红外的激光器,用于医学或其他领域。 第五章研究了石英光子晶体光纤中中红外超连续谱的产生。精心设计了多种具有同种端面结构的光子晶体光纤,光纤端面的六圈空气孔可以分成两组,内三圈主要影响光纤色散,外三圈主要影响光纤损耗。分别使用波长为1550 nm和1950 nm的超短脉冲(皮秒和飞秒)作为泵浦脉冲泵浦光纤。在1550 nm脉冲泵浦下,扩展超连续谱到长波波段的主要机制是孤子自频移效应。无论是用皮秒泵浦脉冲还是飞秒脉冲,超连续谱限制在3000 nm之内。采用零色散点远离泵浦脉冲的光纤,有利于能量分布在超连续谱的长波长段。在1950 nm脉冲泵浦下,使超连续谱往长波长扩展的有效机制是红移色散波的产生。在飞秒脉冲泵浦下,在泵浦脉冲附近色散斜率为负的PCF c中超连续谱的长波长边超过了3 μm。 第六章系统研究了不同光纤特性的悬吊芯光纤中可见光色散波的产生。通过数值模拟,研究了不同泵浦脉冲宽度和不同平均泵浦功率下的色散波产生。当泵浦波长在光纤的反常色散区时,产生孤立的色散波。随着脉冲宽度和泵浦功率的增加,色散波的相干性基本保持不变(~1)。详细分析了超连续谱产生的过程,能量交换主要发生在一阶孤子的第一次收缩时。低的孤子阶数有利于获得高的转换效率。用实验参数进行的数值模拟分析表明,用光栅压缩色散波可以将其压缩到40 fs左右。实验中,在脉冲宽度为50 fs,波长为1 μm的泵浦脉冲泵浦下,由于交叉相位调制效应,在大纤芯的SCF1中产生的独立的色散波在480 nm左右,在小纤芯的SCF2中产生的独立的色散波分别在466 nm和485 nm左右。SCF2中色散波光谱的半高全宽度约为40 nm,转换效率约为10 %。通过比较脉冲序列,色散波的相干性比红外部分的相干性好。低泵浦功率下色散波的产生易受OH的影响。 第七章是总结和展望。超连续谱产生;非线性效应;光子晶体光纤中国科学院上海光学精密机械研究所毕婉君材料学博士
中文题目: 基于微结构光纤的超连续谱技术研究
外文题目: Research on the technology of supercontinuum based on microstructured fiber
作者: 毕婉君
导师姓名: 廖梅松
学位授予机构: 中国科学院上海光学精密机械研究所
答辩时间: 20181227
中文关键词:
超连续谱产生;非线性效应;光子晶体光纤
英文关键词:
Supercontinuum Generation;Nonlinear Effect;Photonic Crystal Fibers
中文摘要:
英文摘要:
文献类型:学位论文
学位级别: 博士
正文语种: chi
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