饱和非线性介质中艾里孤子的产生与传输调控

采用分步傅里叶法,通过数值模拟研究了饱和非线性介质中艾里孤子的产生与传输调控。单艾里光束入射时,在一定的初始振幅范围内可以产生稳定传输的呼吸式孤子。初始振幅增加时,孤子的强度增加,呼吸周期变短,但宽度基本保持不变。衰减系数增加时,孤子的平均峰值强度先增大后减小之后再增大,存在两个极值点。光束入射角度为负值时,形成左倾艾里孤子;光束入射角度为正值时,形成右倾艾里孤子。双艾里光束入射时,入射角同为负值可以减弱光束间的相互作用,入射角同为正值可以增强光束间的相互作用。此外,不同的入射角可以控制孤子或孤子对的传输方向。     

饱和非线性介质中艾里-高斯光束的传输与交互作用

研究了艾里-高斯光束在饱和非线性介质中的传输与交互作用.结果表明,入射光为单艾里-高斯光束时,在一定功率范围内,调节初始振幅与光场分布,可形成传输方向可控的呼吸孤子.当初始振幅增加时,孤子的呼吸周期先减小后增大.入射光为两艾里-高斯光束时,同相位光束相互吸引,两光束中心位置两侧附近产生呼吸孤子和对称孤子对.反相位光束相互排斥,中心位置两侧仅产生对称的孤子对.光场分布越趋于高斯分布,两艾里-高斯光束相互作用就越强,孤子对的数目越少.     

艾里-厄米-高斯光束在克尔介质中的孤子控制

以非线性薛定谔方程为理论模型,采用分步傅里叶数值模拟方法,讨论了有限能量艾里-厄米-高斯光束在克尔介质中的传输特性以及相互作用。研究表明,通过控制介质的非线性强度和艾里-厄米-高斯光束的初始振幅,可以抑制光束的衍射效应,当它们满足一定条件时,能够产生孤子。通过研究两艾里-厄米-高斯光束的相互作用,发现调整两光束的初始间隔以及相位,可以控制孤子的数量和传输方向。     

竞争型非线性介质中艾里-高斯光束交互作用的调控

基于分步傅里叶法研究了艾里-高斯光束在三次聚焦和五次散焦竞争型非线性介质中交互作用的调控.结果表明:当入射角度为零时,同相位艾里-高斯光束相互吸引,五次散焦非线性强度较弱时,可形成周期逐渐缩短的呼吸孤子或强度不变的孤子.五次散焦非线性强度较强时,呼吸孤子的平均宽度变大甚至出现光束分叉现象,形成孤子对.反相位艾里-高斯光束相互排斥,排斥力随五次散焦非线性强度单调递增.当入射角度不为零时,通过控制光束入射角度的正负和初始间距.同相位和反相位艾里-高斯光束交互作用时可以同时表现出相互吸引和排斥的现象.     

有偏压光伏光折变晶体中艾里高斯光束的传输特性

采用分步傅里叶法,数值模拟研究了有偏压光伏光折变晶体中艾里高斯光束的传输特性.结果表明,当艾里高斯光束初始振幅和晶体的外加电场在一定范围内时,可以形成沿直线稳定传输的呼吸式孤子.调节初始振幅或外加电场可以控制孤子的峰值强度和呼吸周期.随着入射光场分布因子的变大,孤子的平均峰值强度先增大后减小,孤子的呼吸周期先变小后变大.随着光束衰减因子的增加,孤子的平均峰值强度先增大后减小,然后再增大.此外,光束入射角为负值时,孤子向左偏移,光束入射角为正值时,孤子向右偏移.入射角只改变孤子的输出位置,不影响孤子的强度、宽度和呼吸周期.     

啁啾艾里光束在非局域介质中的传播特性

本文基于包含非局域非线性效应的非线性薛定谔方程,采用分步傅里叶变换方法,详细研究了竞争非局域非线性介质中啁啾艾里光束的传输动力学特性。结果表明:啁啾可以改变单艾里光束的传输速度,且啁啾越大,脉冲偏移速度越大,但啁啾对光束的呼吸周期和振幅影响却不大。当初始输入为啁啾双艾里光束时,在弱非局域介质中,啁啾会使两光束间的排斥力增强,从而影响孤子的呼吸周期;而在强非局域介质中,两光束的相互作用较为复杂,表现为结构复杂的准周期特性,啁啾会导致准周期结构的周期变化,且随着啁啾绝对值的增大,准周期结构的周期变大,光束衍射增强。     

强非局域介质中1+1维高斯型损耗空间双孤子的相互作用

研究了1+1维高斯型双光束在含小损耗的强非局域非线性介质中的传输特性。通过对该介质中光束传输遵循的非局域非线性薛定谔方程进行近似简化,得到了含小损耗强非局域非线性介质中1+1维高斯型双光束传输模型。在此基础上运用解析的方法研究了双光束传输的演化规律,得到了准双孤子解。经过进一步分析发现,在传输过程中两光束中心的轨迹为艾里函数;两光束会准周期性地碰撞、分离;随着传输距离的增大,两光束中心之间的最大距离会越来越大。另一方面,当损耗逐渐增大时,两光束的碰撞空间周期将变短,同时两光束中心之间的最大距离也越来越大。     

拉曼增益和自陡峭效应对艾里脉冲传输特性的影响

利用包含拉曼增益和自陡峭效应的非线性薛定谔方程, 忽略光纤损耗的情况下, 模拟和分析了艾里脉冲在单模光纤中的传输特性. 发现艾里脉冲在光纤中传输时由于受到拉曼增益和自陡峭效应的影响, 在一定条件下会转变为孤子, 并且, 转变后形成的孤子传播方向发生了偏移. 在时域方面, 艾里脉冲的小峰个数迅速减少, 变成含有一个主峰和次峰能量可以忽略的峰值结构, 此时, 可以把这个峰值结构近似为孤子的结构. 同时发现, 不管截止系数a和艾里函数振幅b 取什么值, 拉曼增益和自陡峭效应都会减小艾里脉冲的时移. 研究了艾里脉冲的加速度特性, 发现一定的传输距离下, 艾里脉冲的横向加速度在初始时并不是一个稳定的值, 但随着传输距离的增大, 加速度慢慢趋于稳定.     

高阶效应对光纤系统中孤子和艾里脉冲传输特性影响的数值研究

以变系数耦合高阶非线性薛定谔方程为理论模型,采用分步傅里叶方法,讨论了孤子和艾里脉冲在光纤中的传输特性。研究表明三阶色散、自频移和自陡峭效应导致孤子和艾里脉冲所分离出的俘获孤子的中心位置发生偏移,且三阶色散会影响俘获孤子的强度,并讨论了两脉冲的中心位置及强度对艾里脉冲截断系数的依赖关系。     

空气中紫外波长局域涡旋光孤子的解及其稳定性

根据紫外波长光束在空气中传输时的非线性效应得到包含氧分子三光子电离等非线性效应的薛定谔方程。由该非线性薛定谔方程出发,研究了紫外波长光束在空气中传输时局域涡旋光孤子的形成。将涡旋孤子的形成和粒子在势阱中的运动联系起来,讨论了光束在空气中形成局域涡旋光孤子的初始条件。数值求解了柱坐标下的涡旋孤子解,随着初始幅值的变化,方程出现单环、双环等孤子解;分析了孤子解光强分布随着传播常数的变化情况,并得出光束尺度和脉冲能量对应初始幅值的变化关系。同时分析了孤子解的扰动稳定性,验证了Skarka所推导的一般性判据。     

Manipulation of Airy Beams in Dynamic Parabolic Potentials

The propagation of finite energy Airy beams in dynamic parabolic potentials, including uniformly moving, accelerating, and oscillating potentials, is investigated. The propagation trajectories of Airy beams are strongly affected by the dynamic potentials, but the periodic inversion of the beam remains invariant. The results may broaden the potential applications of Airy beams, and also enlighten ideas on Airy beam manipulation in nonlinear regimes.     

Persistence and breakdown of Airy beams driven by an initial nonlinearity

We study the behavior of Airy beams propagating from a nonlinear medium to a linear medium. We show that an Airy beam initially driven by a self-defocusing nonlinearity experiences anomalous diffraction and can maintain its shape in subsequent propagation, but its intensity pattern and acceleration cannot persist when driven by a self-focusing nonlinearity. The unusual behavior of Airy beams is examined from their energy flow as well as the Brillouin zone spectrum of self-induced chirped photonic lattices.     

Automatic Fourier transform and self-Fourier beams due to parabolic potential

We investigate the propagation of light beams including Hermite–Gauss, Bessel–Gauss and finite energy Airy beams in a linear medium with parabolic potential. Expectedly, the beams undergo oscillation during propagation, but quite unexpectedly they also perform automatic Fourier transform, that is, periodic change from the beam to its Fourier transform and back. In addition to oscillation, the finite-energy Airy beams exhibit periodic inversion during propagation. The oscillating period of parity-asymmetric beams is twice that of the parity-symmetric beams. Based on the propagation in parabolic potential, we introduce a class of optically-interesting beams that are self-Fourier beams—that is, the beams whose Fourier transforms are the beams themselves.     

Airy光束在Kerr介质中的传输特性

通过对非线性薛定谔方程的研究,得出Airy光束在Kerr介质中的崩塌功率及有效束宽演化的解析表达式。经过数值计算发现,Airy光束在聚焦的Kerr介质中,其主瓣在开始传播时始终是会聚的;当输入功率小于临界崩塌功率时,Airy光束主瓣的中心部分出现局部崩塌。在不同的Kerr介质中, Airy光束的形状和传输轨道均能保持不变,如同在自由空间中传播,但光场大小的分布,随着不同的Kerr介质会发生改变:在Kerr的聚焦介质中,光场向中心聚焦;而在散焦的Kerr介质中,光场会发散。     

Evolution of finite energy Airy beams in cubic-quintic atomic vapor system

In a numerical investigation, we demonstrate the evolution of a one-dimensional and two-dimensional finite energy Airy beam in a Λ-type three-level atomic vapor with linear, cubic, and quintic susceptibilities considered simultaneously with the dressing effect. Quasi-solitons and soliton pairs are observed due to this competition mechanism. We find that the frequency detuning of the pump field and its power greatly affect the formation and evolution of generated solitons. In general, around the two-photon resonance point and for low intensities of the pump field, it is less difficult to form solitons. This investigation enriches the study of the propagation properties of Airy beams and soliton generation in atomic vapor.     

在反常色散区艾里脉冲与光孤子相互作用规律的研究

本文采用分步傅里叶法,研究了在反常色散区孤子和艾里脉冲相互作用的规律,并且对相互作用后的孤子和艾里脉冲各自的强度、时域和时移进行了MATLAB仿真.通过仿真发现光孤子和艾里脉冲在光纤中相互重叠时,交叉相位调制(XPM)就会建立并且这种调制会影响孤子和艾里脉冲的性质.在相互作用过程中,孤子的形状保持不变,但是受到艾里脉冲自加速特性的影响孤子会发生偏移.艾里脉冲受XPM的影响会转化为孤子,传播方向也会发生偏移.可见,XPM使得艾里脉冲和孤子各自的性质都相互影响着对方.艾里脉冲和孤子的时域也会受到XPM的影响,使得原本不相同的脉冲形状都转变为含有一个主峰和一个次峰的相似结构,并且主峰和次峰的位置和脉冲宽度也大致相同,这也是艾里脉冲能够转换为孤子的一个依据.另外本文还模拟了不同输入强度r下的孤子和艾里脉冲的变化情况,模拟发现不管是艾里脉冲还是孤子时移都随着输入强度r的增大而增大,并且它们的变化趋势都是一样的,同时模拟还发现在相同的的r值下,时移也会随着a值的增大而增大.     

Propagations of Airy Beams and Nonlinear Accelerating Optical Beams in Photorefractive Crystals with Asymmetric Nonlocality

The impact of the asymmetric nonlocal diffusion nonlinearity of Airy beams and nonlinear accelerating beams supported by photorefractive crystals is addressed. It is revealed how the asymmetric nonlocal response alters the evolution of these optical beams. It is found that the evolution of these beams presents a bending action under the influence of the diffusion nonlinearity. It is also shown that nonlinear accelerating beams can exist in photorefractive crystals with asymmetric nonlocality. These accelerating solutions have the same Airy‐like tail, and accelerate along parabolic trajectories. Soliton states are formed in the interaction of both in‐phase and out‐of‐phase Airy beams and nonlinear accelerating beams and also present a bending action because of the action of diffusion nonlinearity.     

A theory of Gaussian pulse propagation

The complex-ray representation of Gaussian beams proposed by the author in 1968 is applied to the propagation of pulses with Gaussian envelope. Linear propagation in uniform time-invariant waveguides is first considered. Next, closed-form soliton solutions are obtained for a special kind of nonlinearity.     

Bilinear Forms and Dark-Dark Solitons for the Coupled Cubic-Quintic Nonlinear SchrÕdinger Equations with Variable Coefficients in a Twin-Core Optical Fiber or Non-Kerr Medium*

Twin-core optical fibers are applied in such fields as the optical sensing and optical communication,and propagation of the pulses,Gauss beams and laser beams in the non-Kerr media is reported.Studied in this paper are the coupled cubic-quintic nonlinear Schrodinger equations with variable coefficients,which describe the effects of quintic nonlinearity for the ultrashort optical pulse propagation in a twin-core optical fiber or non-Kerr medium.Based on the integrable conditions,bilinear forms are derived,and dark-dark soliton solutions can be constructed in terms of the Gramian via the Kadomtsev-Petviashvili hierarchy reduction.Propagation and interaction of the dark-dark solitons are presented and discussed through the graphic analysis.With different values of the delayed nonlinear response effect b(z),where z represents direction of the propagation,the linear-and parabolic-shaped one dark-dark soltions can be derived.Interactions between the parabolic-and periodic-shaped two dark-dark solitons are presented with b(z) as the linear and periodic functions,respectively.Directions of velocities of the two dark-dark solitons vary with z and the amplitudes of the solitons remain unchanged can be observed.Interactions between the two dark-dark solitons of different types are displayed,and we observe that the velocity of one soliton is zero and direction of the velocity of the other soliton vary with z.We find that those interactions are elastic.     

Specular and vortical Airy beams

A new kind of truncated Airy beams is investigated and discussed. These beams are a superposition of shifted and truncated Airy functions and its specular counterparts, where zeroes or extremal points of the Airy function are chosen as a truncation point. The specular Airy beams are smooth at the truncation point and produce a diffraction pattern similar to Hermite-Gaussian modes. Under propagation in Fresnel zone, specular Airy beams demonstrate a symmetrical acceleration in opposite sides and the beam divergence is proportional to the traveled distance squared. The astigmatic mode converter transforms a two-dimensional specular Airy beam into a quasi-annular field with a nonzero orbital angular momentum. Vortical Airy beams based on truncated Airy functions are also discussed. These beams are similar to Laguerre-Gaussian modes, while their annular structure is changed during propagation.