基于光子晶体光纤和可编程声光调制器的超短激光脉冲调制技术研究
文献类型：学位论文
| 作者 | 周冰 |
| 学位类别 | 硕士 |
| 答辩日期 | 2007 |
| 授予单位 | 中国科学院上海光学精密机械研究所 |
| 导师 | 冷雨欣 |
| 关键词 | 光子晶体光纤 孤子自压缩 超连续谱 位相匹配 |
| 其他题名 | Study of ultra-short pulse modulation based on photonic crystal fiber and Acousto-Optic programmable dispersive filter |
| 中文摘要 | 光子晶体光纤是近年来兴起的一种具有微结构包层的新型光纤，这种微结构光纤从根本上改变了传统光纤的许多传输特性，获得了传统光纤所没有的各种新的特性。这些奇异特性主要包括：可控色散特性，增强的非线性特性以及无休止的单模特性等。这些优异特性使其成为产生超连续谱的优秀介质.超连续谱被广泛应用于飞秒激光的相位稳定、光学频率测量、光学相干层析成像、超短脉冲压缩、通信光源等领域.基于此,光子晶体光纤极有可能成为比传统光纤更优异的下一代传输光纤,在光通信、高精度光谱学、生物光子学、非线性光学、超短激光脉冲等领域具有广阔的应用前景.因此,研究超短激光脉冲在光子晶体光纤中的非线性传输及超连续谱现象,具有重要学术意义和实际应用价值。 本学位论文在前人的基础上,对超短脉冲在光子晶体光纤中的非线性传输及超连续谱现象进行了一些研究.取得了一些创新性的研究成果： 1.利用二阶分步傅立叶方法通过求解广义非线性薛定谔方程(GNSE),数值计算了相同脉宽和能量的超短脉冲在不同色散参数的光子晶体光纤中非线性传输和超连续谱的产生.比较了超短脉冲在光纤不同色散区传输时,高阶色散和非线性效应对超连续谱的产生以及对脉冲波形演化的影响.结果表明相对于超短脉冲中心波长位于光子晶体光纤的正常和反常色散区,可以相应获得短波波段和长波波段的超连续谱输出，当超短脉冲中心波长位于零色散波长点时,通过色散和非线性效应的联合作用,更易于产生全波长段的平坦超连续谱。 2. 在前人的基础上总结了在保偏光子晶体光纤中,偏振相关的四波混频相位匹配条件,并提出了三种新的匹配过程.利用7fs超短脉冲激光器,验证了当入射脉冲光谱横跨保偏光子晶体光纤正负色散区时,功率相关位相匹配和偏振相关位相匹配同时存在,通过控制入射光的偏振态,使得脉冲光在光纤内发生不同的偏振相关匹配过程,产生不同的反斯托克斯光。 3. 将可编程声光调制器（AOPDF）置于钛宝石KHz 啁啾脉冲放大（CPA）激光系统的振荡源与展宽器之间，补偿CPA系统中的增益窄化及相位畸变问题，使得CPA激光系统输出脉宽由原来的51fs减少至30fs,仅为理论计算值的1.07倍，极大提高了CPA激光系统的性能。 4通过使用可编程声光调制器AOPDF,实验研究了在各阶色散调制不同时,超连续谱的产生特性.发现可以根据不同的需要,调节入射超短脉冲的各阶色散,产生不同频段的超连续谱。 5.基于一般光纤压缩器光路复杂难以调节的问题，提出采用可编程声光调制器AOPDF调节脉冲色散，使得调节后的超短脉冲在光子晶体光纤中传输时，产生的自相位调制SPM与传输时的色散影响相互平衡，产生孤子自压缩的现象。数值模拟了60fs超短脉冲经过压缩后，得到12.5fs孤子自压缩脉冲输出。采用该方法压缩脉冲，光路简单易于操作。 |
| 英文摘要 | As a new kind optical fiber, Photonic crystal fiber with microstructure cladding have many renewed properties: controllable chromatic dispersion., enhanced nonlinear effects,and endless single mode.Depending on these merits ,PCFs have been applied to many aspects including: stability of carrier envelope phase、frequency measurement、optical coherent tomography、pulse compression.With fast development of fabrication,PCF would uncover other domains,thus the study of nonlinear effect and dispersion properties in PCF has great academic significance and practical value. In this dissertation based on the previous researches, we have investigated the nonlinear effects and chromatic dispersion when laser pulse propagated in photonic crystal fiber(PCF).Moreover we have applied the Acousto-Optic programmable dispersive filter to CPA laser system and the generation of supercontinuum in PCF.These achievements mainly include: 1. Using the second order split step Fourier method ,based on nonlinear SchrÖdinger equation(GNSE), We have calculated the nonlinear propagation of ultra-short pulse with the same duration and energy and the generation of super-continuum (SC) spectrum in different chromatic dispersion regions of photonic crystal fibers (PCF). The influence of high order dispersion and nonlinear effects have been analyzed. While the central wavelength of the input pulse is in the normal or abnormal dispersion regions of PCF, the SC of short-wave band or long-wave band is obtained respectively (respect to central wavelength). Comparatively when the central wavelength is at the zero dispersion wavelength (ZWD) point of PCF, the flatter SC of the whole wave-band can be generated depending on the influence of high order chromatic dispersion and nonlinear effect. 2. In contrast to similar processes in traditional birefringent fibre , three new processes have been introduced when the pump pulses are situated in the anomalous GVD region in BPCFs, and ten different phase matching processes in the single mode BPCFs have been brought up.Using pump pulses less than 7fs, whose spectrum spans the normal and the anomalous chromatic dispersion regions of single mode birefringent photonic crystal fiber, the polarization dependent and independent anti-Stokes lines have been emitted and modulated simultaneously. These results are supported by theoretical analysis and numerical simulation. 3.Chirped-pulse amplification (CPA) technique has been widely used to generate ultra-intense femto-second pulses,but the main problems in the CPA system are the gain narrowing and uncompensated phase distortions. In our experiment, Using Acoustic-Optics Programmable Dispersive Filter between the oscillator and the stretcher, the effects of gain narrowing and high-order dispersions on the pulse duration in kHz chirped-pulse amplification system have been pre-compensated, and the spectral FWHM is expanded from 30nm to 50nm . By pre-compensating the high-order phase distortions with the phase measured by SPIDER, we successfully optimize the output duration from 51fs to 30fs, which is 1.07 times Fourier-transform-limitation . 4.The chirp effect in supercontinuum (SC) generation in photonic crystal fibers (PCF) is researched carefully in experiment. Using an Acoustic-optics Programmable Dispersive Filter (AOPDF), the second and third order dispersions of the pulses from femtosecond oscillator can be accurately controlled. The experimental results show the SC generation in PCF is sensitive to the chirp of incident pulse, and the output spectrum and conversion efficiency can be tuned by changing the initial dispersion state. With second order dispersion brought to the incident pulse, we find that large absolute value can enhance the energy conversion to long wavelength, oppositely small value can enhance the conversion to short wavelength. Specially, an optimal negative second order dispersion can maximize the conversion to the shortest one at about 625 nm. The effect of the third order dispersion (TOD) also has been investigated, and we find that the same value of positive and negative TOD has the similar effect on the SC. 5 .To avoid the complex and hard-adjusted experimental setup ,we bring up a new method to compress the laser pulse based on combination of AOPDF and PCF.By using AOPDF, the chromatic dispersion has been introduced to incident pulse ,and when the dispersion-changed pulse propagated in PCF,the pulse is self-compressed due to soliton effect.The initial 60fs pulse has been numerically stimulated,and we get the 12.5fs output. |
| 语种 | 中文 |
| 源URL | [http://ir.siom.ac.cn/handle/181231/16513]  |
| 专题 | 上海光学精密机械研究所_学位论文 |
| 推荐引用方式 GB/T 7714 | 周冰. 基于光子晶体光纤和可编程声光调制器的超短激光脉冲调制技术研究[D]. 中国科学院上海光学精密机械研究所. 2007. |
入库方式： OAI收割
来源：上海光学精密机械研究所
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