Higher-order space-charge field effects on the self-deflection of photovoltaic dark spatial solitons

We investigate theoretically the effects of higher-order space-charge field on the self-deflection of photovoltaic dark spatial solitons by numerical method under steady-state conditions. The expression for an induced space-charge electric field, including higher-order space-charge field terms is obtained. Numerical results indicate that photovoltaic dark solitons possess self-deflection process during propagation, and the solitons always bend in the direction of the c-axis of the crystal. The self-deflection of dark solitons can experience considerable increase especially in the regime of high photovoltaic field strengths. Relevant examples are provided.     

Self-Deflection of Dark Screening Spatial Solitons Based on Higher-Order Space Charge Field

The effects of higher-order space charge field on the self-deflection of dark screening spatial solitons in biased photorefractive crystals are numerically investigated under steady-state conditions. The expression for an induced space-charge electric field including higher-order space-charge field terms is obtained. Numerical results indicate that dark solitons possess a self-deflection process during propagation, and the solitons always bend in the direction of the c axis of the crystal. The self-deflection of dark solitons can experience considerable increase especially in the regime of high bias field strengths.     

闭路光伏暗空间孤子的自偏转特性研究

通过考虑扩散效应的影响,采用数值方法,研究了一维稳态闭路光伏暗空间孤子的自偏转特性。结果表明,在扩散项的影响下,光伏暗空间孤子光束的中心沿一个抛物线轨迹在光折变晶体光轴方向上产生偏转;孤子中心偏转距离随光伏场以及入射孤子波强度的增加而单调增加。光伏暗空间孤子与明孤子的自偏转规律有明显不同。     

温度对双光子亮光伏空间孤子演化特性的影响

基于扩散效应及暗辐射强度对温度的依赖关系,研究了温度对双光子光伏光折变介质中亮光伏空间孤子动态演化及自偏转特性的影响。将亮孤子作为入射孤子波,采用数值方法求解孤波演化方程,结果表明:在给定温度下,双光子光折变介质中可以形成稳定的亮光伏空间孤子,当介质的温度变化不大时,孤子将克服较小的扰动而保持稳定的孤子传播,当温度变化足够大时,孤子将变得不稳定甚至崩溃;在一定温度范围内,孤子中心的自偏转距离随着温度的升高而增加,在特定温度下达到最大值,之后随着温度的升高而减小。     

LiNbO3晶体中屏蔽光伏孤子自偏转的 时空演化与可控因素

基于带输运模型理论建立了 LiNbO₃ 晶体屏蔽光伏孤子的时空演化动力学方程, 用有限差分方法求解发现, LiNbO₃ 晶体中明、暗屏蔽光伏孤子存在大的自偏转, 并且光孤子形状变得具有不对称性, 偏转方向的曲线斜率绝对值变大, 偏转反方向的曲线斜率绝对值变小. 分析研究表明影响其自偏转度和形变的因素包括受主浓度 N_A, 暗辐射强度 I_d 和外加电场 E₀ . 其他条件不变的情况下N_A 越大, 明孤子的自偏转度与形变越小, 暗孤子的自偏转度与形变反而越大; 对于 I_d , 它对明暗孤子的影响是相同的, I_d 越小, 晶体里诱导出的空间电荷场越容易达到饱和, 当信号光中心光强与暗辐射强度之比为 10^-1时无饱和现象产生; 随着 E₀ 数值的增大, 明孤子的自偏转度和形变减小, 而暗孤子的自偏转度和形变反而增大.     

有偏压的光伏光折变晶体中屏蔽光伏孤子的自偏转

修正了有偏压的光伏光折变晶体中屏蔽光伏孤子的理论。用微扰法研究了屏蔽光伏孤子的自偏转，得出孤子光呸中心的运动为抛物线，并且空间频率分量随传播距离而线性移动，改变外偏压或旋转光的偏振方向可以控制其自偏转。当光伏效应可忽略时，屏蔽光伏孤子的非线性波动方程就转化为屏蔽孤子的非线性波动方程，它的自偏转就转化为屏蔽孤子的自偏转。当外偏压为零时，屏蔽光伏孤子的非线性波动方程就转化为光伏孤子的非线性波动方程，它的自偏转证明了光伏孤子中也存在着自偏转。     

Higher-order space charge field effects on the evolution of spatial solitons in biased photorefractive crystals

We investigate higher-order space charge field effects on the evolution of bright spatial solitons in biased photorefractive crystals under steady-state conditions. Numerical simulations demonstrate that these optical solitons can experience considerable increase in their self-deflection especially in the regime of very high bias field strengths. This process is further studied using perturbation techniques. Our analysis indicates, that for very high bias fields, the self-bending process is further enhanced by a factor that varies cubically with the applied field. Relevant examples are provided.     

Steady-State Spatial Solitons in Low-Amplitude Regime in Biased Photorefractive-Photovoltaic Crystals

A theory of the space-charge field is improved in biased photorefractive-phorovoltaic crystals. Steady-state spatial solitons are obtained in the low-amplitude regime in biased photorefractive-photovoltaic crystals. When photovoltaic effect is neglected, these solitons are screening solitons, and their space-charge field is the space-charge field of screening solitons. When the external field is absent, these solitons are photovoltaic solitons for the closed or the open circuit and we also predict that gray solitons exist in photorefractive-photovoltaic crystals, and their space-charge field is the space-charge field of photovoltaic solitons.     

亮暗屏蔽光伏孤子在LiNbO3晶体中的大自偏转

用数值方法证实了亮、暗屏蔽光伏孤子在有外加电场的LiNbO₃晶体中都可以发生大自偏转,并验证了这种自偏转现象不但与晶体中受主浓度N_A有关而且还与外加电场E₀有关. 在E₀相同的条件下,N_A越小这种自偏转现象越明显,在N_A相同的条件下,E₀越大自偏转现象越明显. 还发现亮、暗屏蔽光伏孤子的自偏转现象不同：亮屏蔽光伏孤子整体都发生明显偏转,暗屏蔽光伏孤子的偏转只是发生在一侧,其极值位置和另一侧几乎不发生偏转. 关键词： 自偏转 空间孤子 光折变效应     

温度对闭路光伏明空间孤子演化和自偏转的影响 (英文)

通过考虑扩散效应的影响，采用数值方法研究了温度对光伏光折变介质中的明空间孤子演化和自偏转的影响。结果表明，当晶体温度变化时，明孤子可以呈现为稳定态、较大周期的压缩和膨胀态，或塌陷态。同时，明空间孤子中心偏转距离随温度增加而增加，在一个特定温度处达到最大值，之后随温度增加而减小，在高温和低温区域此偏转距离趋于零。孤子的最大偏转距离和对应的特定温度随入射孤子波强度的增加而增加。进一步采用微扰方法研究了明孤子自偏转过程，其结果与数值方法获得的结果一致。     

光伏暗孤子和灰孤子的自偏转

分别用数值法和微扰法研究了考虑背景光时光伏暗空间孤子的自偏转特性.与亮孤子不同，暗孤子光束中心的运动轨迹不为抛物线.在归一化的直角坐标系(ξ,ζ)中，暗孤子朝ξ>0的方向偏转；同时，暗孤子光束中心光强发生改变.通过调节晶体对信号光和背景光的有效光伏系数之比r或信号光光强可以控制它的自偏转.还用数值方法研究了灰空间孤子的自偏转特性，发现灰孤子光束自偏转特性依赖于横向初速度v.当v>0时，灰孤子光束朝ξ>0的方向 关键词： 光伏空间暗孤子 光伏空间灰孤子 扩散效应 自偏转     

Self-deflection of partially spatially incoherent beams and solitons in photovoltaic photorefractive crystals

By considering the effect of background light and diffusion, the self-deflection process of partially spatially incoherent (PSIC) beams and photovoltaic (PV) solitons in open-circuit PV photorefractive crystals has been investigated by employing numerical method and the perturbation technique, respectively. The results from the two approaches are in good agreement: the center of PSIC PV solitons moves on a parabolic trajectory, which is similar to those of coherent solitons. In addition, we also discuss that the dependence of self-deflection effect on the coherent parameter θ₀ and find it is slight relative to θ₀ for quasi-soliton but decreases monotonously with θ₀ for PSIC beam.     

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.     

高阶效应影响下高阶孤子在超常介质中的传输特性研究

基于描述超短脉冲在超常介质中传输的非线性薛定谔方程,本文数值研究了高阶效应影响下高阶亮、暗孤子在超常介质中的传输情况。数值模拟表明,三阶色散和自陡峭效应都会引起高阶孤子的分裂和辐射,破坏高阶亮孤子周期性演化特性,导致高阶暗孤子分裂出的灰孤子不对称;孤子的阶数越高,三阶色散和自陡峭的影响越大。利用超常介质可控的色散和非线性特性,通过调节三阶色散和自陡峭效应的系数,发现超常介质中可以基本支持二阶亮孤子、二阶暗孤子和三阶暗孤子的稳定演化。本文的研究结果为将来进一步研究超常介质中高阶亮、暗孤子的存在及传输特性提供了一定的参考价值。     

Effects of dark soliton crystal temperature on the self-deflection of bright soliton in a biased serial photovoltaic photorefractive crystal circuit

Based on the theory of one-dimensional separate soliton pairs formed in a serial photovoltaic photorefractive crystal circuit, the effects of the dark soliton crystal temperature on the self-deflection of the bright one in a bright-dark soliton pair are investigated. The numerical results indicate that the spatial shift of the bright soliton can experience obvious increase in their self-deflection with the increase of the temperature of the dark soliton. The self-bending process is further studied using perturbation techniques and the results are found to be good agreement with that obtained by numerical method.     

One-dimensional steady-state bright photovoltaic solitons in LiNbO3:Fe crystal with background illumination

We investigate theoretically and experimentally one-dimensional bright photovoltaic solitons in LiNbO₃:Fe crystal by use of the background illumination. We find that, in LiNbO₃:Fe crystal, bright photovoltaic solitons can be obtained with background illumination for κ>1, where κ is the ratio of the background illumination photovoltaic constant to the soliton optical beam's photovoltaic constant. For κ<1, dark photovoltaic solitons are generated. On the other hand, our experiments show good agreement with theoretical prediction for the soliton existence curve in a special intensity ratio.     

Temperature effect on dissipative holographicscreening-photovoltaic solitons in a biased dissipative system

In a biased dissipative photovoltaic-photorefractive system, this paper investigates the temperature effect on the evolution and the self-deflection of the dissipative holographic screening-photovoltaic （DHSP） solitons. The results reveal that, the evolution and the self-deflection of the bright and dark DHSP solitons are influenced by the system temperature. At a given temperature, for a stable DHSP soliton originally formed in the dissipative system, it attempts to evolve into another DHSP soliton when the temperature change is appropriately small, whereas it will become unstable or break down if the temperature departure is large enough. Moreover, the self-deflection degree of the solitary beam centre increases as temperature rises in some range, while it is decided by the system parameters and is slight under small-signal condition. The system temperature can be adjusted to change the formation and the self-deflection of the solitary beam in order to gain certain optical ends. In a word, the system temperature plays a role for the DHSP solitons in the dissipative system.     

弱光强空间屏蔽光伏明孤子的动态演化特性

在忽略晶体损耗和扩散效应的情况下，讨论了加外电场的光伏光折变晶体中弱光强空间屏蔽光伏明孤子及其演化特性，在弱光强条件下得到了空间屏蔽光伏明孤子的解析解表达式，与运用数值计算的方法所得到的结果十分吻合，该方法解决了以往数值求解动态演化方程时必须先数值求解常数分方程或积分方程的问题，讨论了参量失配情况下空间屏蔽光伏明孤子的动态演化特征。     

Effects of the temperature on steady-state bright spatial solitons in biased centrosymmetric photorefractive crystals

We provide a theoretical investigation of effects of the temperature on the steady-state bright solitons in centrosymmetric photorefractive crystals. Three physical factors related to the effects of the temperature, i.e., the dielectric constant, diffusion process and dark irradiance, are considered. Our results show that both the intensity profile and self-deflection of solitons strongly depend on the crystal temperature and the dielectric constant temperature dependence dominates the process.     

有偏压的光伏光折变晶体中的空间孤子

证明了有偏压的光伏光折变晶体中存在着明、暗稳态的空间孤子.它源于对外电场的非均匀空间屏蔽和光伏效应.与已报道的稳态光折变空间孤子相比,它具有不同的特性.当外电场为某一特定值时,用改变外电场的极性和旋转光的偏振方向可以实现明孤子与暗孤子的相互转换.当外电场足够强可以忽略光伏效应时,它类似于屏蔽孤子;当不存在外电场时,它类似于开路条件下的光伏孤子. 关键词：