Coupling effects for grey separate spatial solitons in a biased series photorefractive crystal circuit with both the linear and quadratic electro-optic effects

The existence and coupling of grey–grey separate spatial solitons in a biased series photorefractive crystal circuit with both the linear and quadratic non-linearity is investigated in this paper. The numerical solution of the grey–grey separate spatial solitons is presented. The effect of coupling between the two separate spatial solitons and the influence on each soliton due to the input intensity and crystal’s temperature is analysed. Changing the intensity of the soliton in one crystal affects the soliton in both crystals due to flow of the light induced current through the circuit. Also, the effect of changing the temperature of one crystal affects the soliton in both crystals due to the coupling effect. The soliton width dependence on the temperature is different for each crystal.     

Separate spatial soliton pairs in a biased series centrosymmetric photorefractive crystal circuit

It is shown theoretically that three types of separate soliton pairs: bright-bright, bright-dark, and dark-dark, can be established in a biased series circuit consisting of two centrosymmetric photorefractive crystals and the two solitons in a separate soliton pair can affect each other by the light-induced current. The effects of the intensities of soliton beams and background lights on the normalized profiles of solitons are discussed.     

Self-deflection of steady-state bright spatial solitons in biased centrosymmetric photorefractive crystals

The effects of diffusion on self-deflection of steady-state bright spatial solitons in biased centrosymmetric photorefractive crystals are investigated systematically by both numerical and perturbation methods. The results show that the soliton propagates along a parabolic trajectory and the central spatial frequency component shifts linearly with the propagation distance. Both the deflection effects vary cubically with applied external bias field.     

中心对称光折变材料中的小光强空间孤子

给出了小光强条件下中心对称光折变材料中光波演化方程的亮、暗及灰空间孤子解析解，并推导出了孤子宽度的显式表达式． 关键词： 光折变效应 光折变材料 空间孤子     

The temperature properties of spatial optical solitons in biased photorefractive crystal

The effect of temperature on the evolution and the self-deflection of bright screening solitons has been investigated using numerical methods and the perturbation technique. The numerical study shows that a bright solitary beam could be stable, exhibit larger cycles of compression and expansion or break up when the crystal temperature changes. It is also found that the bending distance of the solitary beam centre increases, reaching its maximum value at a characteristic temperature, and then decreases as the temperature increases, approaching zero at low and high temperatures. Both the maximum value of the bending distance and the characteristic temperature increase with the input power density. The self-deflection of the bright solitary beam is further studied by the perturbation technique, and the results are found to be in good agreement with that obtained from the numerical method. The crystal proposed here is strontium barium niobate (SBN: 60).     

外加电场光折变有机聚合物串联回路中独立空间孤子对

对外加电场光折变有机聚合物串联回路中独立空间孤子对进行了理论研究,导出了在光折变有机聚合物串联回路中两光束传播的耦合方程,证明了串联回路中存在暗-暗、明-暗和明-明三种独立空间孤子对.在光束的空间展宽远小于有机聚合物宽度的极限条件下,暗-暗孤子对之间孤子入射光强的改变可相互影响到对方的包络和动态演化.对于明-暗孤子对,暗孤子通过光电流能影响明孤子,但明孤子不能影响暗孤子.明-明孤子对之间没有影响. 关键词： 非线性光学 光折变效应 光折变聚合物 空间孤子对     

Dynamic behavior of spatial bright solitons in a biased transversely shifting photorefractive crystal

We have observed and simulated the dynamic evolution of a beam launched into a biased transversely shifting photorefractive crystal. Propagating in this scheme, the beam can trap into spatial solitons and then deflect to the beam shifting side. The deflected amplitude of solitons relates to the shifting velocity of the sample (beam). At a higher shifting velocity, the bending amplitude of the beam will be decreased. We attribute this bending to the nonlinear relaxation effect present in the samples. The experiment and the simulation show fairly good agreement.     

有外加电源的串联光折变晶体回路中的独立空间全息-哈密顿屏蔽孤子对

在由两块垂直于光轴两端面镀上电极的光折变晶体和一个外加电源组成的串联光折变晶体回路中, 在适当的条件下可以形成独立空间全息-哈密顿屏蔽孤子对. 这种孤子对共有四种类型:明-明、暗-暗、明-暗以及暗-明. 当入射光束的空间展宽尺寸远小于晶体宽度时, 孤子对中的哈密顿暗孤子可以通过光感应电流影响另一个孤子, 而哈密顿明孤子和全息孤子则不能影响另一孤子.     

Separate holographic screening soliton pairs in a biased series photorefractive crystal circuit

Holographic dark (bright) screening solitons are predicted in one dimension for a series circuit consisting of two photorefractive crystals connected electronically by electrode leads in a chain with a voltage source. Each crystal can support a holographic screening soliton. The two solitons are known collectively as a separate holographic screening soliton pair with three types: bright--bright, bright--dark and dark--dark. The numerical results show that the two solitons in a soliton pair can affect each other through a light-induced current and their coupling can affect their spatial profiles under the limit in which the optical wave has a spatial extent much less than the width of the crystal.     

Screening-photovoltaic grey spatial soliton families in biased two-photon photovoltaic photorefractive crystal

To study the grey spatial soliton families in biased two-photon photovoltaic photorefractive crystal, the dynamical evolution equation and the numerical solution of the grey spatial soliton families were established. The numerical results show that the incoherently coupled screening-photovoltaic grey soliton families can be established provided the multiple incident beams have the same polarization, wavelength, and are mutually incoherent. The screening-photovoltaic grey soliton families can be considered as the united form of screening grey soliton families and open- or closed-circuit photovoltaic grey soliton families due to two-photon photorefractive effect.     

Gap solitons supported by optical lattices in biased centrosymmetric photorefractive crystals

We analyze the existence and stability of gap solitons supported by optical lattices with self-focusing nonlinearity in biased centrosymmetric photorefractive crystals. It is shown that, in first finite bandgap, gap solitons are symmetric in transverse dimension, single humped, entirely positive and linearly stable, while these solitons are antisymmetric with similar profiles, the stable and unstable intervals of the gap solitons are intertwined in the second finite bandgap.     

有外加电源的串联光折变晶体回路中的独立空间全息-哈密顿屏蔽孤子对

在由两块垂直于光轴两端面镀上电极的光折变晶体和一个外加电源组成的串联光折变晶体回路中, 在适当的条件下可以形成独立空间全息-哈密顿屏蔽孤子对. 这种孤子对共有四种类型:明-明、暗-暗、明-暗以及暗-明. 当入射光束的空间展宽尺寸远小于晶体宽度时, 孤子对中的哈密顿暗孤子可以通过光感应电流影响另一个孤子, 而哈密顿明孤子和全息孤子则不能影响另一孤子.     

Separate Holographic-Hamiltonian screening soliton pairs in a biased series photorefractive crystal circuit

Separate Holographic-Hamiltonian screening soliton pairs are predicted in a biased series photorefractive crystal circuit consisting of two photorefractive crystals connected electronically by electrode leads in a chain with a voltage source. The existence of four types of the separate soliton pairs: dark–dark, bright–dark, dark–bright and bright–bright in such a circuit is proved. Under the limit in which the spatial extent of the optical wave is much less than the width of the crystal, the Hamiltonian dark soliton can affect the other soliton by the light-induced current whereas the Hamiltonian bright soliton and holographic soliton cannot affect the other soliton in the soliton pair.     

Temporal behavior of spatial solitons in centrosymmetric photorefractive crystals

We investigate theoretically the time behavior of spatial solitons in biased centrosymmetric photorefractive crystals. A one-dimensional time-dependent wave propagation equation in biased centrosymmetric photorefractive crystals is presented. It is shown that the bright solitons exist in both quasi-steady-state and steady-state regimes for high saturation values. When the intensity ratio is smaller than unity, the bright soliton width decreases monotonically to a minimum value toward steady state. Moreover, the time-dependent nonlinear wave equation exhibits only steady-state screening dark spatial solitons.     

加偏压中心对称双光子光折变晶体中多变量空间灰孤子

 为了得到有偏压的中心对称双光子光折变晶体中存在多变量空间灰孤子的结果,基于中心对称双光子光折变晶体中空间灰孤子的基本理论,采用数值方法推导出了中心对称双光子多变量空间灰孤子归一化包络解的积分形式,并对其特性进行研究。结果表明：这种多变量空间灰孤子是由多束偏振方向和波长都相同的互不相干光束耦合形成的。当多变量空间灰孤子只包含有1个或2个光束分量成分时,它自动退化到中心对称双光子空间灰孤子或中心对称双光子非相干耦合灰 灰空间孤子对的情况。当这一多变量空间灰孤子在有偏压的中心对称双光子光折变晶体中传播时,各分量成分光束都能稳定传播。     

Holographic solitons in centrosymmetric photorefractive crystals

The conditions necessary for obtaining holographic solitons in centrosymmetric photorefractive crystals are discussed. When both the intensity modulation of the two interacting waves and the angle between the vector of each beam and the longitudinal axis are small, centrosymmetric photorefractive crystals with a positive (or negative ) effective quadratic electro-optic coefficient are able to support bright (or dark) holographic solitons. The intensity width at half maximum of bright and dark solitons is inversely proportional to the external bias field. The holographic solitons can also exit in dissipative centrosymmetric photorefractive crystals when the applied external bias field is large enough.     

有偏压光折变晶体中的小振幅行波孤子

利用行波变换法，推导出有正偏压光折变晶体中小振幅光波的行波正、负孤子解，证明在有正偏压光折变晶体中存在着正、负行波孤子；研究行波正、负孤子在光折变晶体中的传播，同已报道的稳态光折变空间孤子相比，它们具有不同的特性，行波正、负孤子在晶体中都表现为亮孤子，其幅度和宽度不变，传播中沿着直线的轨迹偏转，调整系统参数可以任意控制偏转角度. 关键词： 行波孤子 行波变换 光折变晶体 偏转     

Gray spatial solitons in biased two-photon photovoltaic photorefractive crystals

This paper predicts that gray spatial solitons can exist in biased two-photon photovoltaic photorefractive crystals. Under appropriate conditions and in the steady state, the gray spatial solitons solution of the optical evolution equation is obtained. The properties associated with these solitons, such as their intensity profile, intensity full width at half-maximum, width, transverse velocity and phase distribution, are discussed as functions of their normalized intensity and degree of “grayness”. Relevant examples are provided.     

Spatial solitons in centrosymmetric photorefractive media

We predict spatial solitons in photorefractive centrosymmetric media driven by the dc Kerr effect.     

Steady-state bright-dark vector spatial solitons in biased two-photon photorefractive crystals

We show that bright-dark vector solitons are possible in biased two-photon photorefractive crystals under steady-state conditions. The analytical solutions of these vector solitons can be obtained if the intensities of the two vector components are approximately equal. When the intensities of the two vector components differ, the vector soliton pair solutions can be determined using simple numerical integration procedures. The stability of the bright-dark vector solitons has been investigated numerically.