Interaction of nonlocal incoherent spatial solitons

We investigate numerically the interaction of nonlocal incoherent spatial solitons in strongly nonlocal kerr media based on the coherent density approach. Numerical simulations show that the incoherent soliton position is very similar to the case of coherent soliton, and show that the incoherence plays an important role in the soliton interaction, while the role of other parameters such as the phase difference, the separation, the extent of nonlocality and the input power play in the interaction is very similar to the case of nonlocal coherent soliton. Some interesting numerical examples are presented to illustrate their interaction behavior further. Pertinent physics features are addressed.     

Multiple incoherent gray photorefractive spatial solitons

We show that an even-number sequence of multiple incoherent gray photorefractive spatial screening solitons is possible. When the external voltage is small, only an incoherent Y-junction photorefractive spatial screening soliton is generated, corresponding to the lowest order in the even-number incoherent soliton sequence. When the external voltage is increased, the incoherent gray soliton beam splits into an even-number sequence of multiple incoherent gray photorefractive spatial screening solitons. For a given physical system such an even-number sequence of multiple incoherent gray photorefractive spatial screening solitons is obtained by either increasing the external voltage and decreasing the full width half maximum (FWHM) of the beam’s intensity or increasing the external voltage and decreasing the beam’s grayness.     

多个部分非相干光孤子的相互作用

基于相干密度理论，数值地研究了在饱和对数非线性介质中多个部分非相干光空间孤子之间的相互作用. 数值结果表明，在非相干参量较小情况下，非相干光孤子的相互作用与相干光孤子的相互作用规律较类似. 当非相干参量较大时，强的非相干性模糊了孤子之间的相位关系，孤子间的相互作用主要以非相干相互吸引作用为主. 特别是在非相干参量较大而且孤子初始相对相位差为π的情况下，多个部分非相干光孤子可并行传播形成稳定的阵列孤子. 利用多个非相干光孤子的不同相互作用形态写入各种阵列波导，为实现光控制光、导向光提供了一种可能性. 关键词： 多个部分非相干光空间孤子 空间光孤子的相互作用 相干密度理论 饱和对数非线性     

Bright spatial solitons on a partially incoherent background

We present the first observation of incoherent antidark spatial solitons in noninstantaneous nonlinear media. This new class of soliton states involves bright solitons on a partially incoherent background of infinite extent. In the case where the nonlinearity is of the Kerr type, their existence is demonstrated analytically by means of an exact solution. Computer simulations and experiments indicate that these incoherent antidark solitons can propagate in a stable fashion provided that the spatial coherence of their background is reduced below the incoherent modulation instability threshold.     

Interaction of two-dimensional spatial incoherent solitons in photorefractive medium

We present a review of our recent theoretical and experimental results on the interaction of incoherent two-dimensional solitary beams in PR SBN crystals. We show that the inherent anisotropy of PR nonlinearity strongly affects the interaction between solitons. Theoretical and experimental results reveal that solitons interacting in a plane perpendicular to the direction of external biasing field always attract, whereas those colliding in a plane of the field exhibit anomalous behaviour. They may experience both attractive and repulsive forces, depending on their mutual separation. We also show that this anisotropy results in the complicated topology of soliton trajectories, featuring periodic collisions, prolonged mutual spiraling and collapse, depending on the initial conditions. Received: 16 November 1998 / Revised version: 12 February 1999 / Published online: 12 April 1999     

Dark incoherent spatial solitons in logarithmically saturable nonlinear media

This paper studies numerically the dark incoherent spatial solitons propagating in logarithmically saturable nonlinear media by using a coherent density approach and a split-step Fourier approach for the first time. Under odd and even initial conditions, a soliton triplet and a doublet are obtained respectively for given parameters. Simultaneously, coherence properties associated with the soliton triplet and doublet are discussed. In addition, if the values of the parameters are properly chosen, five and four splittings from the input dark incoherent spatial solitons can also form. Lastly, the grayness of the soliton triplet and that of the doublet are studied, in detail.     

Stability properties of multiwavelength, incoherent, dissipative spatial solitons

We have investigated the interaction between two dissipative spatial solitons of different frequencies in periodically patterned semiconductor optical amplifiers. The experimental results are in good agreement with the theory. Simulations suggest that multiwavelength interactions do not produce stable bound solitons unless the system's modeling equations are completely symmetric.     

Observation of mighty morphing spatial solitons

The experimental observation of bright spatial solitons in the form of mighty morphing solitons is reported for the first time to the author's knowledge. These are Gaussian-like beams of elliptical cross section, which appear to change their shape constantly as they propagate. Saturation of the nonlinear medium is shown to progress logarithmically.     

完全非相干白光一维光生伏打暗空间孤子

使用白炽灯作光源在LiNbO₃∶Fe晶体内实验观察到一维白光光生伏打暗空间孤 子. 由奇数 和偶数初始条件分别产生了灰孤子和灰孤子对，它们所感应的波导能导向白光和相干光. 用 相干光清楚地探测到它们内部的多模结构. 该实验证明了白光光生伏打暗空间孤子的存在， 并指出了用完全非相干的白光暗孤子控制和导向相干光的可能性. 关键词： 光生伏打效应 自陷 完全非相干孤子 波导     

Interaction of incoherent white-light solitons

We study numerically the formation and interactions of incoherent white-light solitons in a nonlinear media with logarithmic saturable nonlinearity based on the coherent density approach. We find that not only the formation but also the interactions of incoherent white-light solitons are fundamentally a collective effect, where all the frequencies participate in the process, and self-adjust their respective contributions to the formation and interactions. We find that the interactions of incoherent white-light solitons in logarithmic media are always attractive.     

向列相液晶中空间光孤子的观测

分别以He-Ne激光器、半导体激光器和Ar⁺激光器作为光源照射液晶材料，在低光强入射的情况下均观察到了光束的自聚焦现象以及空间光孤子的形成，观察到了长度l>5mm的孤子波和多模空间光孤子，并对空间孤子的产生条件及特性进行了讨论. 关键词： 自聚焦 空间光孤子 向列相液晶     

Waveguides formed by incoherent dark solitons

We demonstrate experimentally optical guidance of coherent light beams, using incoherent light. Such guidance is made possible by generation of partially spatially incoherent self-trapped dark beams (dark incoherent solitons) in a noninstantaneous nonlinear medium. In the one-dimensional case, the incoherent solitons induce single and Y-junction planar waveguides, whereas in the two-dimensional case, they form circular waveguides. These experiments introduce the possibility of controlling high-power laser beams with low-power incoherent light sources such as LED's or lightbulbs.     

Observation of quadratic spatial solitons in periodically poled lithium niobate

We report what are to our knowledge the first observation and characterization of quadratic spatial solitons in periodically poled lithium niobate (PPLN). Using a Nd:YAG (1064-nm) source, we observed self-trapped solitary-wave propagation over more than six diffraction lengths as a result of the cascaded quadratic nonlinear process. Low-threshold operation (5-kW peak power) was measured for the quasi-phase-matched PPLN structure designed for frequency doubling.     

Observation of optical spatial solitons in a highly nonlocal medium

We report on the observation and quantitative assessment of self-trapped pulsating beams in a highly nonlocal nonlinear regime. The experiments were conducted in nematic liquid crystals and allow a meaningful comparison with the prediction of a scalar theory in the perturbative limit, while addressing the need for beyond-paraxial analytical treatments.     

Internal mode of incoherent photovoltaic vector solitons

The internal modes of incoherent vector solitons (IVSs) in photovoltaic photorefractive materials are investigated in the framework of coupled nonlinear Schr\"{o}dinger equations. It is found that there is a pair of internal modes corresponding to a bright--bright IVS. The propagation dynamics of the bright-bright IVS perturbed by the internal modes is simulated by numerical method.     

Elliptic incoherent spatial solitons and their interactions in strongly nonlocal media with an anisotropic nonlocality

We investigate the propagation and interaction of elliptic incoherent spatial solitons (EISS) in strongly nonlocal kerr media with an anisotropic nonlocality based on the coherent density approach. An exact analytical solution of such EISS is obtained; the results show that such EISS can form with both isotropic and anisotropic coherence. Moreover, we find that the interaction properties of EISS are very similar to that of their coherent counterpart. Some numerical examples are presented and pertinent physics features are addressed.     

Elliptic incoherent solitons in saturable nonlinear media

We identify elliptic incoherent spatial solitons in isotropic saturable nonlinear media. These solitary states are possible, provided that their correlation function is anisotropic. The propagation dynamics of this new class of solitons are investigated by use of numerical simulations. We find that, during a collision event of two such elliptic solitons, their intensity ellipse rotates, and at the same time their centers of gravity tend to revolve around each other.     

Observation of interaction forces between one-dimensional spatial solitons in photorefractive crystals

We propagate two coherent and parallel beams of a He-Ne laser through a Bi(12)TiO(20) photorefractive crystal in the presence of drift nonlinearity. Our experimental results demonstrate that the beams attract or repel each other according to their initial phase difference. They attract each other when they are initially in phase and they repel each other when they are initially out of phase. These experimental results agree with numerical predictions recently published.     

Optical spatial solitons

Optical and Quantum Electronics - It is almost common knowledge now that particles also possess properties of waves. But, can localized wave-packets behave and interact like particles? This article...