飞秒光脉冲基于交叉相位调制的压缩脉冲对的产生

数值模拟了在喇曼散射效应影响下,波长位于反常色散区的高阶孤子泵浦脉冲与波长在正常色散区的信号脉冲通过交叉相位调制作用产生的压缩脉冲对.结果表明,由于受喇曼效应的影响,飞秒信号脉冲产生的脉冲对不再保持对称,滞后的蓝移脉冲峰值功率随传输距离的增加而减小,产生孤子红移.同时发现喇曼系数增大,超前红移脉冲峰值功率增加,滞后蓝移脉冲峰值功率降低.分析了孤子阶数和正、负走离效应对脉冲压缩对变化规律的影响.     

飞秒光脉冲基于交叉相位调制的压缩脉冲对的产生

数值模拟了在喇曼散射效应影响下,波长位于反常色散区的高阶孤子泵浦脉冲与波长在正常色散区的信号脉冲通过交叉相位调制作用产生的压缩脉冲对.结果表明,由于受喇曼效应的影响,飞秒信号脉冲产生的脉冲对不再保持对称,滞后的蓝移脉冲峰值功率随传输距离的增加而减小,产生孤子红移.同时发现喇曼系数增大,超前红移脉冲峰值功率增加,滞后蓝移脉冲峰值功率降低.分析了孤子阶数和正、负走离效应对脉冲压缩对变化规律的影响.     

色散缓变光纤中飞秒高阶孤子脉冲的增强压缩

提出了一种利用孤子绝热放大效应与高阶孤子脉冲压缩效应相结合来压缩飞秒高阶孤子的新方法.通过数值模拟方法证明,采用三阶色散为负的色散缓变光纤压缩高阶孤子,可利用喇曼散射效应与负三阶色散的相互作用,消除正三阶色散对光脉冲压缩产生的不利影响,增加压缩比,提高压缩后光脉冲的质量.研究表明,在色散缓变参量一定的情况下,孤子阶数越高,所需最佳光纤长度越短、光脉冲的压缩比越大;对于相同功率的孤子光脉冲,光脉冲的压缩比随着色散缓变参量的增大而增大;无论是孤子脉冲还是高斯脉冲都适合于色散缓变光纤中的高阶孤子脉冲压缩.     

受激喇曼散射对自相似脉冲产生的影响

研究了在受激喇曼散射与三阶色散共同作用下,自相似脉冲在具有正常色散的色散渐减光纤中的演化情况.结果表明:在同一个传输距离上,当考虑受激喇曼散射与三阶色散的共同影响时,脉冲中心的不对称特性相对好转;产生中心漂移与边缘振荡较只有三阶色散作用时要减弱,啁啾仍然具有很强的线性特性,但是线性范围减小,导致频谱的窄化以及对接下来自相似脉冲的压缩产生了不利影响;而且光纤长度的延长并没有起到展宽啁啾线性范围的效果,反而导致严重的啁啾非线性;因此对脉冲进行压缩后,压缩脉冲质量较不考虑受激喇曼散射时要差.     

光纤喇曼放大泵浦光与信号光的关联研究

分析了信号光入射后可能发生的效应基于电磁场理论,综合光纤受激喇曼散射(SRS)效应、建立了光纤喇曼放大泵浦光与斯托克斯光、信号光的关联方程,给出了系统增益形成正反馈条件的表达式,结果表明:在光纤参量满足增益正反馈的条件下,当SRS增益对应于非饱和增益工作状态时入射信号光得到放大,SRS增益愈高则放大倍数愈高,并有区段上SRS增益相对低时其关联程度相对高.     

单模光纤中喇曼类孤子脉冲理论研究

本文在考虑群速度色散(GVD)、受激喇曼散射(SRS)、自相位调制(SPM)、交叉相位调制(XPM)及光纤损耗同时作用的条件下,建立了关于单模光纤中喇曼类孤子的理论计算模型。通过模拟计算Gouveia-neto等人的实验,得到了84fs的喇曼类孤子脉冲,与其实验结果基本一致,并给出了喇曼类孤子脉冲形成过程的图象和新见解。 关键词：     

单模光纤中受激喇曼散射对调制不稳定性的影响

基于修正的非线性薛定谔方程，利用线性扰动理论和数值方法研究了单模光纤中的调制不稳定性.由于受激喇曼散射的作用，使得喇曼增益谱叠加到光纤中的调制不稳定性增益谱上.这样，原本调制稳定的光纤正常色散区也出现了调制不稳定性；而在反常色散区，随着初始功率的增加，常规的调制不稳定性增益谱的增益和频谱范围均增大，而喇曼增益谱的增益增大但其频谱范围基本不变，这样导致常规的不稳定区域逐渐侵入并最终掩盖喇曼增益区.数值模拟验证了解析结果的正确性，并证明了利用反常色散情形下的调制不稳定性可以产生超短脉冲序列，但这种脉冲序列的进一步传输将会出现喇曼孤子自频移现象.     

压缩系数可控的光脉冲压缩器

提出了一种压缩系数可控的光脉冲压缩器.该脉冲压缩器主体包括梳状色散分布光纤（CDPF）和喇曼放大器两部分.梳状色散分布光纤由多段色散位移光纤和单模光纤拼接而成,具有喇曼增益介质的功能.对一给定的光脉冲序列,可以通过控制泵浦功率实现脉冲压缩器的压缩率可调.通过对非线性薛定锷方程的数值模拟,这一光脉冲压缩器的性能得到了验证.当光脉冲在CDPF中传输时,脉冲得到压缩并且被放大.对喇曼泵浦功率来改变可以得到不同的输出脉宽.通过优化CDPF的结构,得到了喇曼泵浦功率和压缩系数之间很好的线性关系.     

宽频带聚焦泵浦准稳态受激电子喇曼散射的增益因子和能量转换效率

本文采用Raman-Maxwell-Bloch方程,计算了宽频带聚焦泵浦准稳态受激电子喇曼散射的增益因子和能量转换效率.在计算中考虑了泵浦抽空、喇曼介质对泵浦光的吸收和喇曼介质的泡和效应.计算结果与XeCl激光在钡蒸汽中的受激喇曼散射实验基本上符合.     

光纤中强受激喇曼散射时的自相位调制

在光纤-光栅对激光脉冲压缩中,由于受激喇曼散射和自相位调制的竞争,使得泵浦激光脉冲波形重整,且自相位调制谱极不对称。本文用2m的单模保偏光纤,在产生较强的受激喇曼散射的情况下,得到较为对称的泵浦激光的自相位调制功率谱,并讨论了自相位调制功率谱的一些特点。     

Dispersion and nonlinear management for femtosecond optical solitons

We consider the concept of femtosecond propagation for optical solitons in a dispersion management fiber and study the optimal amplification of optical solitons through dispersion wells and barriers and also for the dispersion tailored profile case. For the former, we observed periodic soliton trapping for the in-phase injection case when their respective velocities were equal and opposite with their amplitudes being unequal and no soliton trapping for the off-phase injection case when the two pulses are having a phase difference of π. For the latter, we observed an enormous amplification of the soliton pulses which is one of our main results in this Letter.     

非均匀光纤中暗孤子传输特性研究

由于变系数非线性Schrödinger方程的增益、色散和非线性项都是变化的, 根据方程这一特点可以研究光脉冲在非均匀光纤中的传输特性. 本文利用Hirota方法, 得到非线性Schrödinger方程的解析暗孤子解. 然后根据暗孤子解对暗孤子的传输特性进行讨论, 并且分析各个物理参量对暗孤子传输的影响. 经研究发现, 通过调节光纤的损耗、色散和非线性效应都能有效的控制暗孤子的传输, 从而提高非均匀光纤中的光脉冲传输质量. 此外, 本文还得到了所求解方程的解析双暗孤子解, 最后对两个暗孤子相互作用进行了探讨. 本文得到的结论有利于研究非均匀光纤中的孤子控制技术.     

光纤中基于拉曼放大与脉冲压缩的超短光孤子产生

提出一种在单模光纤负群速色散枢由弱脉冲产生高强度超短光孤子的新方法。     

Conservation laws,modulation instability and solitons interactions for a nonlinear Schrödinger equation with the sextic operators in an optical fiber

Under investigation in this paper is a sextic nonlinear Schrödinger equation, which describes the pulses propagating along an optical fiber. Based on the symbolic computation, Lax pair and infinitely-many conservation laws are derived. Via the modiied Hirota method, bilinear forms and multi-soliton solutions are obtained. Propagation and interactions of the solitons are illustrated graphically: Initial position and velocity of the soliton are related to the coefficient of the sixth-order dispersion, while the amplitude of the soliton is not affected by it. Head-on, overtaking and oscillating interactions between the two solitons are displayed. Through the asymptotic analysis, interaction between the two solitons is proved to be elastic. Based on the linear stability analysis, the modulation instability condition for the soliton solutions is obtained.     

Experimental observation of orthogonally polarized time-delayed optical soliton trapping in birefringent fibers

Propagation of two orthogonally polarized time-delayed optical solitons in low-birefringence optical fiber is studied experimentally. We demonstrate soliton trapping and collisions and also the ability to control the separation and shape of soliton pulses by varying the power at the input of the fiber.     

Interaction of solitons through radiation in optical fibers with randomly varying birefringence

Propagation of solitons in optical fibers is studied taking into account the polarization mode dispersion (PMD) effect. We show that the soliton interaction caused by the radiation emitted by solitons due to the PMD disorder leads to soliton jitter, and we find its statistical properties. The theoretical predictions are justified by direct numerical simulations.     

Performance improvement by positioning DCF non-symmetrically in a periodic amplified re-circulating loop for long-haul optical soliton transmission link

In this paper, we have carried out simulative performance analysis by positioning the DCF non-symmetrically in a periodic amplified re-circulating loop for optical soliton transmission link over a long haul. The investigations indicate that relatively stable pulses can propagate in a mid-compensated optical soliton transmission over a long-haul dispersion-managed soliton regime in a fiber link with loss and periodic amplification by keeping the average dispersion small but non-zero. Here non-zero anomalous fiber dispersion equal to 6 ps/nm is maintained by inserting DCF in the beginning, middle and end of the fiber loop. Here it is demonstrated that solitons can propagate even when β₂ varies along the fiber length up to transmission distance of 18,000 km.     

光纤中飞秒基孤子压缩的一种改进性方法

本文报道利用色散缓变光纤压缩飞秒基孤子的一种改进性方法.研究表明,选取三阶色散为负的色散缓变光纤能够大大改善孤子脉冲的压缩效果.     

Bright and dark solitons in the normal dispersion regime of inhomogeneous optical fibers: Soliton interaction and soliton control

Symbolically investigated in this paper is a nonlinear Schrödinger equation with the varying dispersion and nonlinearity for the propagation of optical pulses in the normal dispersion regime of inhomogeneous optical fibers. With the aid of the Hirota method, analytic one- and two-soliton solutions are obtained. Relevant properties of physical and optical interest are illustrated. Different from the previous results, both the bright and dark solitons are hereby derived in the normal dispersion regime of the inhomogeneous optical fibers. Moreover, different dispersion profiles of the dispersion-decreasing fibers can be used to realize the soliton control. Finally, soliton interaction is discussed with the soliton control confirmed to have no influence on the interaction. The results might be of certain value for the study of the signal generator and soliton control.     

Soliton dynamics of megawatt ultrashort light pulses in a hollow photonic-crystal fiber: Effect of high-order dispersion and retarded nonlinearity

The properties of megawatt optical solitons in hollow photonic-crystal fibers (PCFs) are studied. We demonstrate regimes where high-power laser pulses can be compressed to a few cycles of light field and identify the main tendencies in the soliton dynamics of ultrashort laser pulses in hollow PCFs originating from dispersion properties and limited transmission band of such waveguides. The influence of retarded nonlinearity on the soliton dynamics of high-power laser pulses in a hollow PCF is analyzed. In a multisoliton regime, retarded nonlinearity and high-order dispersion are shown to result in the formation of high-power pulses displaying no oscillations of their temporal envelope, which would be typical of standard high-order solitons.