Modulational instability of incoherently coupled beams in azobenzene-containing polymer with photoisomerization nonlinearity

The modulational instability of two incoherently coupled beams in azobenzene-containing polymer with photoisomerization nonlinearity is investigated analytically and numerically. Our results show that as a precursor to spatial optical soliton formation, modulational instability can be adjusted and controlled by the wavelength combinations of the signal and background beams. We also discuss the dependences of strength of modulational instability on intensities of two signal beams and background beam. These findings make it possible to predict the formation of incoherently coupled soliton pairs in azobenzene-containing polymer.     

复色光光伏空间孤子

提出了双色信号光、单色背景光的光伏空间孤子理论,并获得了亮孤子解.用Cu:KNSBN晶体作介质,获得了复色信号光、单色背景光的复色光光伏空间亮孤子 关键词： 光伏空间孤子 复色光     

Dark and bright photovoltaic spatial solitons in photorefractive crystals with positive refractive-index perturbation

We have demonstrated, for what is believed to be the first time, that in a photorefractive crystal with positive refractive-index perturbation a two-dimensional dark or bright photovoltaic spatial soliton can be formed in the same crystal by a signal beam and a background beam of different wavelengths. We discuss the conditions on the effective Glass constants and the absorption coefficients of the background and signal beams in determining the formation of the spatial soliton.     

Modulation instability of bright photovoltaic solitons on a partially incoherent background

We present the observation of incoherent anti-dark photovoltaic solitons in LiNbO₃:Fe crystal. This new class of soliton states involves bright photovoltaic solitons on a background beam meeting ?? > 1, where ?? is the ratio of background illumination photovoltaic constant to that of soliton beam. For ?? < 1, dark photovoltaic solitons are generated. Furthermore, this novel type solitons are investigated experimentally by injecting coherent light and partially coherent background of infinite extent. In case of spatial coherence of the background lower than the threshold of incoherent modulation instability, these results indicate that bright photovoltaic solitons can propagate in a stable fashion.     

Evolution of Dark Spatial Soliton in Quasi-phase-matched Quadratic Media

We theoretically investigate the evolvement of dark spatial soliton with cascading quadratic nonlinearity in quasi-phase-matched second harmonic generation. It is shown that the dark solitary wave can propagate stably when background intensity is large enough, in which diffraction of beam can be balanced by the cascading quadratic nonlinearity. We also analyze the influence of phase-mismatch on the stability of dark soliton propagation.     

光致异构聚合物中相互作用光学空间孤子对的垂直光调控

采用数值法研究了在具有光致异构非线性的聚合物中平行传播的光学空间孤子对(信号光)被另一束垂直入射光调控的情况.调节调控光和信号光的初始相位差、调控光入射位置等可以使信号光孤子产生合成、分开等现象，对此给出了物理解释.这种相互作用的空间光孤子被垂直光调控的现象可望应用于光合成、光互联、光波导等方面. 关键词： 光学空间孤子对 相互作用 垂直光调控 光致异构     

Generalized Theory of One-Dimensional Steady-State Optical Spatial Solitons

We present a generalized soliton theory based on the one-dimensional generalized nonlinear Schroedinger equation,from which one can easily obtain the bright, dark, and grey soliton waveforms, and their existence curves. We show that the forming conditions of spatial solitons are directly dependent on the relationship between the index perturbation and the intensity, no matter whether the index perturbation is positive or negative. Some relevant examples are presented when the solitons are supported by the photoisomerization nonlinearity.     

All-optical steering of the interactions between multiple spatial solitons in isotropic polymers

All-optical steering of the nonlinear interactions between multiple spatial solitons can be performed in an isotropic photoisomerization polymer, by propagating an external control beam in perpendicular direction. Fusing, giving birth to another new soliton, and transferring energy can take place in the interactions of signal beams, which can be achieved by changing the incident position of the control beam, the initial relative phase and the power ratio between the signal beams and the control beam. These phenomena are physically explained, and they have significantly potential applications in optical signal readdressing, logic gating, and all-optical switching, etc.     

All optical quasi-steady-state photorefractive spatial solitons

We have created a one- (rather than two-) dimensional quasi-steady-state photorefractive spatial soliton induced by a laser beam instead of an applied electric field. The formation of this type of spatial soliton depends on the intensity of the self-trapped beam, which is different from quasi-steady-state spatial solitons reported in the literature. The optically induced spatial soliton can be exploited in all optical switching applications.     

双色光光伏空间孤子的形成条件及其应用

以折射率改变为正的光伏晶体为例，讨论在其中形成双色光光伏空间孤子的条件-一般而言，在满足上述条件的情况下，双色光可以形成双色光亮孤子、双色光暗孤子、一亮一暗孤子-对于一个波长的光（ray2）单独不能形成亮孤子（它的Glass系数与背景光的Glass系数之比R2小于１）的情况，如果再加上一束另一个波长的光（ray1），且其Glass系数与背景光的Glass系数之比R1大于１，则在一定条件下，这个双色光中两个颜色的光可以都形成亮孤子-还讨论了ray1的光强对孤子宽度的影响- 关键词： 双色光 光伏 空间孤子 全光开关     

Coherence enhancement of spatially incoherent light beams through soliton interactions

We show that the spatial coherence of a partially incoherent light beam can be greatly enhanced through an energy-conserving interaction with an incoherent or a coherent dark spatial soliton. Computer simulations show that during this process a portion of the incoherent beam is trapped within the dark notch of the dark soliton, thus forming a sharp intensity spike. In this region the correlation length dramatically increases by at least 2 orders of magnitude.     

Internal reflection of one-dimensional bright spatial solitons

We study the reflection of one-dimensional spatial solitons at the non-linear interface between a Kerr-type medium and a linear medium. Our study places emphasis on determining the physical conditions under which the beam reflected by the non-linear interface is still a spatial soliton. We find that for small angles of incidence an elastic internal reflection takes place, in the sense that the reflected soliton is essentially the same as the incident one. For incidence angles near a critical angle, the reflected soliton becomes less intense and its reflection angle is smaller than the angle of incidence. Finally, for spatial solitons with input angles well above the critical angle, the main part of the energy is transmitted to the linear medium, and no soliton is internally reflected.     

非相干耦合的亮和暗光伏空间孤子对的偏转特性

采用数值方法研究了在一个具有扩散效应的光伏光折变晶体中的非相干耦合的亮和暗光伏空间孤子对的偏转特性.结果表明,由于非相干相互作用,晶体中的一个亮孤子和一个暗孤子互相俘获,且两个孤子的中心沿着相同的轨迹移动.发现,当亮孤子的入射峰值强度不变时,通过调节暗孤子的入射背景强度可以控制亮孤子的偏转;当暗孤子的入射背景强度处于一个特殊值时,亮孤子的偏转被抑制,而当暗孤子的入射背景强度偏离这个特殊值时,亮孤子发生偏转.同样,当暗孤子的入射背景强度不变时,其偏转可以通过调节亮孤子的入射峰值强度来控制.     

有限高斯背景下空间暗光孤子自诱导波导的模式分析

从有限高斯背景下空间暗光孤子诱导折射率分布出发，用等效衰减矢量法得到它所自诱导的波导的色散特性，并与理想情况的无限背景下空间暗光孤子诱导的色散方程进行了比较。结果表明，当高斯背景越来越宽时，它与无限背景下的结果越来越接近，为在全光器件中实际应用提出了理论依据。     

Interaction of a nonlinear spin-wave and magnetic soliton in a uniaxial anisotropic ferromagnet

We study the interaction of a nonlinear spin-wave and magnetic soliton in a uniaxial anisotropic ferromagnet. By means of a reasonable assumption and a straightforward Darboux transformation one- and two-soliton solutions in a nonlinear spin-wave background are obtained analytically, and their properties are discussed in detail. On the background of a nonlinear spin-wave the amplitude of the envelope soliton has the spatial and temporal period, and soliton can be trapped only in space. The amplitude and wave number of spin-wave have the different contribution to the width, velocity, and amplitude of soliton solutions. The envelope of solution hold the shape of soliton, and the amplitude of each envelope soliton keeps invariability before and after collision which shows the elastic collision of two envelope soliton on the background of a nonlinear spin-wave.     

Wobbling phenomena with logarithmic law nonlinear Schrödinger equations for incoherent spatial Gaussons

We apply the equivalence particle principle to several nonlinear Schrödinger equations (NLSEs) that model the propagation of a spatial beam with logarithmic law nonlinearity. Using this principle, expressions for acceleration, spatial frequency, spatial period and other variables for a spatial soliton can be derived from the solution of the homogenous NLSE with logarithmic law nonlinearity. These results agree well with numerical simulations of the perturbed NLSE. We show that if the expression of the acceleration is bounded this means the spatial soliton propagates with a swing effect.     

Slow-light spatial solitons

We numerically and experimentally report the observation of slow-light spatial solitons in a Kerr medium owing to light amplification by stimulated Raman scattering. This was achieved in a CS2 nonlinear planar waveguide that possesses both a strong self-focusing nonlinearity to generate the spatial Raman soliton and a Raman susceptibility sharp enough to induce the slow-light process simultaneously. We show that the Raman Stokes component is optically delayed by more than 120 ps for a 140 ps Raman pulse duration and only 3 cm of propagation length, while propagating as a spatial soliton beam.     

无偏压的串联光折变晶体回路中高斯光束传播特性调节

根据串联光折变晶体回路中独立空间孤子对理论,研究了明暗孤子对之间的相互依赖特性.假设一束暗孤子波和一束高斯光束分别入射到回路中两块晶体上,利用数值计算方法讨论了改变其中暗孤子光束的强度对高斯光束在另外一个晶体中传播特性的影响.结果表明,调节暗孤子的强度能够影响高斯光束的传播特性,可以决定高斯光束在晶体中是否能够演化为稳定传播的明孤子波 关键词： 非线性光学 光折变效应 光折变空间孤子对 高斯光束     

全光双准稳态空间孤子

观察到一种双准稳态光折变空间孤子.这种孤子是(1+1)维的.它的形成不需要外加电场,是全光的.孤子的形成过程具有全光开关效应 关键词： 光折变空间孤子 双准稳态 全光开关     

Symmetry-breaking instability of multimode vector solitons

We show experimentally that the two-component multimode spatial optical vector soliton, i.e., a two-hump self-guided laser beam, exhibits in Kerr media a sharp space-inversion symmetry-breaking instability. The experiment is performed in a CS2 planar waveguide using the orthogonal circular polarization states of light as the two components of the vector soliton.