光纤中基于交叉相位调制的超短光脉冲串的产生

提出一种在单模光纤正常色散区由连续波产生超短光脉冲串的新方法，即让连续波和一个波长位于光纤正常色散区的调制脉冲串在光纤中同时传输，交叉相位调制效应和群速度色散效应的相互作用能使连续波演化成一串超短光脉冲，其脉冲宽度比调制脉冲串中的脉宽要小得多，本文还通过计算机模拟，对这一方法进行了全面的考察和分析。结果表明，该方法不仅实用，而且可取得较好的效果。     

单模光纤中基于交叉相位调制的压缩脉冲对产生

基于波长位于反常色散区强泵浦脉冲的交叉相位调制,通过对波长位于正常色散区的弱脉冲在单模光纤中的传输进行数值模拟,得出了一种压缩脉冲的新方法.计算结果表明,在零色散波长位于弱脉冲波长和泵浦脉冲波长中间附近的情况下,交叉相位调制(XPM)与群速度色散(GVD)的共同作用能使弱脉冲演化成比其初始宽度窄得多的脉冲对.同时我们还发现,泵浦脉冲的相对于信号脉冲初始峰值功率愈高,初始相对宽度越小,所得弱脉冲的压缩比和压缩后脉冲峰值功率愈高,压缩到最窄时所需光纤长度越短.最后对基于这一压缩的物理机制作了详尽的分析.     

光纤中基于互相位调制效应的超短光脉冲对的产生

提出一种在单模光纤正常色散区由连续波产生超短光脉冲对的新方法.即让连续波和一个波长位于光纤负色散区的高阶孤子在光纤中同时传输,互相位调制效应和群速度色散效应的互相作用能使连续波演化成超短光脉冲对.本文还通过计算机模拟,对该方法进行了全面的考察和分析.结果表明,此方法实用且效果较好.     

基于脉冲对交叉相位调制的亮脉冲的压缩

提出了一种利用色散位移光纤(DSF)压缩波长位于光纤正常色散区的亮脉冲的方法.即让亮脉冲与一个中心波长位于光纤反常色散区的强脉冲对在光纤中共同传输,在适当条件下,交叉相位调制(XPM)效应会导致亮脉冲的压缩.通过分步傅里叶方法(SSFM)对这一压缩过程进行数值模拟和分析,结果表明高斯脉冲的脉宽被压缩了9.8倍,峰值功率增加了6.5倍,且该方法可以有效地避免脉冲走离效应,使脉冲获得更好的压缩效果.     

纳米光纤的色散特性及其超连续谱产生

通过数值计算,分析了纳米光纤的色散特性,并比较了纳米光纤中不同直径和不同材料的色散特性.结果表明：二氧化硅纳米光纤有两个零色散波长,随光纤直径的增大,其色散曲线趋于平坦,零色散波长也随之发生改变;硅光纤只有一个零色散波长,且随着直径的增大,零色散波长向长波方向移动.采用广义非线性薛定谔方程来描述超短激光脉冲在纳米光纤中的传输演化过程,利用分步傅里叶方法求解方程.比较了超短脉冲在光纤不同色散区传输时,色散对超连续谱产生的影响以及脉冲波形的演化.在正常色散区,超连续谱谱宽很窄,而在零色散区和反常色散区则可产生 关键词： 色散 超连续谱产生 非线性光学 纳米光纤     

光纤正常色散区基于脉冲对交叉相位调制的亮脉冲压缩

提出了一种利用单模光纤压缩波长位于光纤正常色散区的亮脉冲的新方法．即让亮脉冲与一个中心波长同样位于光纤正常色散区的强脉冲对在光纤中同时传输，在适当条件下，交叉相位调制效应会导致亮脉冲的压缩．还通过计算机模拟，对这一压缩方法进行了全面的考察和分析．发现与其它压缩方法相比，该方法不仅更实用，而且可获得更好的压缩效果 关键词：     

色散缓变光纤耦合器中的调制不稳定性

用奇偶超模对光纤耦合器的耦合模方程重写.讨论了当输入条件使奇偶超模其中之一被单独激发时,色散缓变光纤耦合器中的调制不稳定性,结合调制不稳定性,分析了色散缓变光纤耦合器在准连续波条件下的非线性效应.结果表明：在正常和反常色散区存在新型调制不稳定性.当满足一定条件时,在色散缓变光纤耦合器中传播的准连续波光束可以分解成脉冲序列,并且脉冲几乎不展宽,由此可以分离和提取稳定的超短脉冲;当输入功率一定时,增益谱随着传输距离的改变,形态基本保持不变;当传输距离一定时,增益谱随着输入功率的增强,宽度变宽,强度增强.     

连续调谐多波长主动锁模光纤激光器

利用色散补偿法纤增加腔内色散和改变调制频率,在主动锁模光纤环形激光器实验中,得到了可连续调谐的双波长激光脉冲,冷却掺铒光纤,实现了17波长的激光。     

超短激光脉冲在不同色散参量光子晶体光纤中传输的数值模拟

为了使得数值模拟更为精确,采用广义非线性薛定谔方程(GNSE)描述超短激光脉冲在光子晶体光纤中的传输演化过程,并利用二阶分步傅里叶方法通过求解方程,数值计算了相同脉宽和能量的超短脉冲在不同色散参量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。     

基于光纤简并四波混频的可调谐波长转换器的优化设计

分析了光纤零色散波长、光纤长度、信号光频率及泵浦功率对基于光纤简并四波混频的可调谐波长转换器调谐带宽和转换效率的影响．结果表明对应不同的零色散波长都存在唯一的最优信号光频使得调谐带宽达到最大,进而推导了最优信号光频和最大调谐带宽的解析表达式,给出了提高此类器件调谐带宽和泵浦效率,减少调谐中输出信号功率起伏的优化设计方法．与以往实验结果相比优化后同等泵浦功率下调谐带宽可增加10nm,若保证同样的调谐带宽则可将泵浦功率降低4．6dB．     

Continuous-wave pumping in the anomalous- and normal-dispersion regimes of nonlinear fibers for supercontinuum generation

Supercontinuum (SC) growth in highly nonlinear fibers is compared for cw pumping in the anomalous- and normal-dispersion regimes. For anomalous-dispersion pumping, the combined effects of modulation instability (MI) and stimulated Raman scattering (SRS) contribute to spectral broadening. Furthermore, breakup of the cw light into ultrashort pulses by MI leads to the formation of a Raman pulse that evolves into a soliton, as evidenced by the observation of soliton self-frequency shift. Blueshifted, nonsolitonic radiation associated with the fission of higher-order solitons is also present in the SC spectra. For normal-dispersion pumping, SRS seeds the SC growth by generating several cascaded Stokes orders. When the Stokes orders are shifted into the anomalous-dispersion regime at higher launch powers, MI again causes soliton formation. Broadband continua are generated when the laser is positioned as far away as 191 nm from the zero-dispersion wavelength in normal dispersion.     

一种基于非线性光纤环镜开关特性的超短光孤子产生方法

提出了一种利用非线性光纤环镜的开关特性将连续波同时转化为亮孤子和暗孤子的新方法 ,即让连续波和另一波长的调制脉冲串共同耦合入光纤环镜 ,交叉相位调制使得一部分连续波被环镜透射 ,其余部分被反射 ;再让透射波和反射波分别在反常色散光纤和正常色散光纤中传输 ,自相位调制和群速度色散之间的相互作用使得透射波和反射波分别演化为亮、暗孤子。数值计算表明 ,该方法不仅可产生脉宽比调制脉冲窄、重复频率比调制脉冲高的亮孤子和暗孤子 ,而且几乎可将全部的连续波能量转化为孤子能量。     

Widely tunable femtosecond fiber optical parametric oscillator

The phase-matching condition in a fiber is discussed. A balance among the different orders of fiber dispersion can be found to achieve a widely tuning modulation instability gain for pumping around the normal dispersion regime. Three coupled nonlinear wave equations are used to simulate the femtosecond fiber optical parametric oscillator. The numerical results show that, through appropriate choice of dispersion, femtosecond pulses with a 180-nm tunable range can be generated when pump wavelength near a fiber’s zero-dispersion wavelength is tuned only 7 nm. Further tuning is limited by the walk-off between the pump and the signal pulses.     

Visible cw-pumped supercontinuum

We report the experimental demonstration of a visible supercontinuum in the cw pumping regime. A 20 W ytterbium fiber laser at 1.06 microm is used to pump a photonic crystal fiber whose zero-dispersion wavelength decreases along the fiber length. Visible wavelengths are generated in the fundamental mode via trapping of dispersive waves by redshifted solitons.     

Experimental Observation of Bright and Dark Solitons Mode-Locked with Zirconia-Based Erbium-Doped Fiber Laser

We demonstrate the generation of dark and bright solitons with our homemade zirconia-based erbium-doped fiber and graphene oxide(GO) saturable absorber in anomalous dispersion region.The GO is fabricated using an abridged Hummer's method,which is combined with polyethylene oxide to produce a composite film.The film is sandwiched between two optical ferrules and embedded in the laser cavity to enhance its birefringence and nonlinearity.The self-starting bright soliton is easily generated at pump power of 78 mW with the whole length cavity of 14.7 m.The laser produces the bright pulse train with repetition rate,pulse width,pulse energy and central wavelength being 13.9 MHz,0.6 ps,2.74 p J and 1577.46 nm,respectively.Then,by adding the 10 m of single mode fiber into the laser cavity,dark soliton pulse is produced.For the formation of dark pulse train,the measured repetition rate,pulse width,pulse energy and central wavelength are 8.3 MHz,20 ns and 4.98 p J and1596.82 nm,respectively.Both pulses operate in the anomalous region.     

具有三个及四个零色散波长光子晶体光纤的仿真研究

利用多极法对光子晶体光纤的色散特性进行了模拟, 通过设计合适的结构参数, 得到了具有3个零色散波长的单模光纤.对中心纤芯有1个微小空气孔光子晶体光纤的色散特性进行了分析, 设计出了具有4个零色散波长的色散曲线.分析了零色散波长随光纤结构的变化规律, 这些零色散波长的位置和间距可以在很大波长范围内灵活调节. 具有多个零色散波长的光纤可以得到色散值极低的超平坦色散曲线. 多个零色散波长光纤能产生丰富的相位匹配曲线, 可以有效地控制光孤子及超短脉冲的四波混频及共振散射产生的光谱特性.     

High-speed photonically assisted analog-to-digital conversion using a continuous wave multiwavelength source and phase modulation

A more simple photonically assisted analog-to-digital conversion system utilizing a cw multiwavelength source and phase modulation instead of a mode-locked laser is presented. The output of the cw multiwavelength source is launched into a dispersive device (such as a single-mode fiber). This fiber creates a pulse train, where the central wavelength of each pulse corresponds to a spectral line of the optical source. The pulses can then be either dispersed again to perform discrete wavelength time stretching or demultiplexed for continuous time analog-to-digital conversion. We experimentally demonstrate the operation of both time stretched and interleaved systems at 38 GHz. The potential of integrating this type of system on a monolithic chip is discussed.     

Route to broadband blue-light generation in microstructured fibers

We explore theoretically the possibility of generating broadband blue light by copropagating a short soliton pump pulse and a broader signal pulse in a microstructured fiber with a zero-dispersion wavelength located between the center wavelength of the pump and the signal pulses. We show that the unique properties of microstructured fibers should allow for broadening of the signal pulse's spectrum by as much as a factor of 50 through the conjugate action of cross-phase modulation and a soliton self-frequency shift. The physical mechanism that leads to this large spectral broadening is analyzed by use of an extended nonlinear Schr?dinger equation.     

Supercontinuum generation in chloroform-filled photonic crystal fibers

We propose a novel method to achieve highly nonlinear photonic crystal fiber (PCF) by filling highly nonlinear liquid chloroform in the core of hollow-core PCF (HCPCF). The dispersion properties and electric field distribution of the fundamental mode are calculated by using the full-vector finite element method (FVFEM). Simulation results indicate that the zero-dispersion wavelength (ZDWL) of the chloroform-filled PCF is adjustable around 800 nm. Hence the femtosecond laser pulses with central wavelength at 800 nm can propagate in anomalous dispersion regime of the PCF, inducing the spectra broadening.