屏蔽光伏孤子诱导的非线性光波导

从理论上研究了由一维稳态屏蔽光伏孤子诱导的非线性波导,结果表明在加偏压的光伏光折变晶体中,例如铌酸锂,无论是明孤子还是暗孤子都能诱导出非线性波导.推导出了在一般条件和低振幅条件下探测光束满足的波方程.     

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

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｓｔｅａｄｙ ｓｔａｔｅｐｈｏｔｏｒｅｆｒａｃｔｉｖｅ (ＰＲ)ｓｐａｔｉａｌｓｏｌｉｔｏｎｓ[1～ 3] ｈａｖｅｂｅｅｎｉｎｖｅｓｔｉｇａｔｅｄｅｘｔｅｎｓｉｖｅｌｙｉｎｔｈｅｐａｓｔｆｅｗｙｅａｒｓ.Ａｔｐｒｅｓｅｎｔｔｈｅｓｅａｒｅｔｗｏｄｉｆｆｅｒｅｎｔｋｉｎｄｓｏｆｓｔｅａｄｙ ｓｔａｔｅＰＲｓｏｌｉｔｏｎｓ :ｓｃｒｅｅｎｉｎｇ[1 ,2 ] ｓｏｌｉｔｏｎｓａｎｄｐｈｏｔｏｖｏｌｔａｉｃ (ＰＶ) [3]ｓｏｌｉｔｏｎｓ.Ｍｏｒｅｒｅｃｅｎｔｌｙ ,ｗｅｈａｖｅｓｈｏｗｎｔｈｅｏ…     

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.     

闭路光伏灰孤子诱导的波导

理论分析了闭路光伏晶体中灰孤子诱导的波导.研究发现,闭路光伏灰孤子诱导的波导在不同孤子灰度值,电流密度和光强比率下均为单模,文中光强比率指孤子峰值强度与暗辐射之比.研究结果解释了闭路光伏灰孤子限制在中心的能量随着电流密度的增加而增加,随着孤子灰度值和光强比率的增加而减小.文章还提供了光伏晶体的相关例子.     

Low-amplitude Screening-photovoltaic Spatial Solitons in Biased Photovoltaic Photorefractive Crystals

The low-amplitude spatial solitons in biased photovoltaic photorefractive crystals are investigated theoretically. The analytical solutions for both the bright and the dark low-amplitude screening-photovoltaic spatial solitons in photorefractive crystals are obtained. The expressions for the width of these solitons are given. The explicit expressions for the spatial deflection and angular deviation of the bright low-amplitude screening-photovoltaic spatial soliton are also presented by taking into account the effect of diffusion.     

Low-amplitude Screening-photovoltaic Spatial Solitons in Biased Photovoltaic Photorefractive Crystals

1　Ｉｎｔｒｏｄｕｃｔｉｏｎ　　Ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｓｐａｔｉａｌｓｏｌｉｔｏｎｓｈａｖｅａｔｔｒａｃｔｅｄｇｒｅａｔａｔｔｅｎｔｉｏｎｉｎｔｈｅｐａｓｔｙｅａｒｓ[1～ 11] .Ｔｈｅｙｈａｖｅｂｅｃｏｍｅｏｎｅｏｆｃｏｎｓｉｄｅｒａｂｌｅｓｕｂｊｅｃｔｓｉｎｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｎｏｎｌｉｎｅａｒｏｐｔｉｃｓ .Ｕｐｏｎｉｌｌｕｍｉｎａｔｉｏｎ ,ｐｈｏｔｏｒｅｆｒａｃｔｉｖｅｍａｔｅｒｉａｌｓｃａｎｓｅｔｕｐｓｐａｃｅ ｃｈａｒｇｅｆｉｅｌｄｉｎｃｒｙｓｔａｌｓ,ｗｈｉｃｈｗｉｌｌｉ…     

Spatial Optical Solitons in Planar Waveguides Based on Electrooptical Crystals

The characteristics of spatial optical solitons in planar waveguides based on electrooptical crystals can differ essentially from the corresponding characteristics for a three-dimensional medium. The main experimental findings relating to the effects of the formation of spatial optical solitons and their interaction in optical waveguides in lithium niobite and strontium – barium niobite crystals at very low light intensities are discussed.     

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。     

Temporal Behavior of Low-Amplitude Grey Spatial Solitons in Biased Two-Photon Photorefractive Crystals

The temporal property of grey screening spatial solitons due to two-photon photorefractive effect in low-amplitude regime is analyzed. The results indicate that a broad solitons is generated at the beginning, and as time evolves, the intensity width of grey solitons decreases monotonically to a minimum value toward steady state. In the same propagation time, the FWHM of solitons decreases with ρ increasing or m decreasing. Moreover, the formation time of solitons is independent of ρ and m. The time isclose to a constant determined by the dielectric relaxation time.     

Temporal Behavior of Low-Amplitude Grey Spatial Solitons in Biased Two-Photon Photorefractive Crystals

The temporal property of grey screening spatial solitons due to two-photon photorefractive effect in lowamplitude regime is analyzed. The results indicate that a broad solitons is generated at the beginning, and as time evolves, the intensity width of grey solitons decreases monotonically to a minimum value toward steady state. In the same propagation time, the FWHM of solitons decreases with p increasing or m decreasing. Moreover, the formation time of solitons is independent of p and m. The time is close to a constant determined by the dielectric relaxation time.     

部分空间非相干暗光伏孤子诱导一维波导研究

在光折变晶体LiNbO3∶Fe中观察到部分空间非相干光形成的一维暗光伏孤子,并由此暗光伏孤子在该晶体中诱导出一维波导.暗光伏孤子是由光折变晶体的强光伏效应产生,是晶体自散焦效应和衍射效应相平衡的结果;此外,光伏孤子的形成还依赖于光束的传播方向和晶体光轴与强度梯度的相对方向.在一维情况下,非相干光孤子诱导出单一的平面波导,能够对弱光敏的强光进行导光.实验证明了用低能量非相干光束控制转换高能量相干光束的可能性.     

温度对中心对称光折变稳态暗孤子演化的影响

为了得到温度对中心对称光折变晶体中空间暗孤子影响的结果,数值研究了中心对称光折变暗孤子动态演化的温度特性。结果表明,孤子强度包络演化强烈地依赖于晶体的温度和介电常数的温度特性。在290-320K的温度变化范围内,暗孤子的宽度随温度的增加而变大,孤子的峰值强度随温度的增加而变小。在300K的温度下,中心对称光折变介质中可以形成稳定的暗空间孤子,当温度从300K升高或降低时,孤子将克服较小的扰动而保持稳定的传播。通过调整温度可以改变孤子的空间形态。     

有偏压中心对称光折变晶体中的屏蔽孤子

给出了中心对称光折变晶体中屏蔽孤子的高阶空间电荷场.当高阶项可以忽略时,这个电荷场就变为早前在中心对称光折变晶体中研究的屏蔽孤子的空间电荷场.研究了中心对称光折变晶体中屏蔽孤子的高阶非线性波动方程.在适当的条件下,这个非线性波动方程能够展示明暗空间光孤子.这类晶体不同于非中心对称晶体,其非线性折射率的改变来源于二次电光效应,而不是一般的线性电光效应.应用光束传播的方法,对这些孤子的稳定性进行了讨论.表明在小的微扰下这类孤子是稳定的,不会发生分裂.     

Bright-Dark Manakov Solitons in Biased Guest-Host Photorefractive Polymer

It is shown that bright-dark Manakov solitons can be formed in biased guest-host photorefractive polymer when the total intensity of two components is much lower than the background illumination.The existing conditions of bright-dark Manakov solitons are discussed in detail.The intensity profiles and dynamical evolutions of solitons are presented by numerical methods.     

Two-Dimensional Spatial Solitons in Nematic Liquid Crystals

We study the propagation of spatial solitons in nematic liquid crystals, using the self-similar method. Analytical solutions in the form of self-similar solitons are obtained exactly. We confirm the stability of these solutions by direct numerical simulation, and find that the stable spatial solitons can exist in various forms, such as Oaussian solitons, radially symmetric solitons, multipole solitons, and soliton vortices.     

Hybrid Parametric Solitons in Nonlinear Photonic Crystals

We analyze the characteristics of a three-frequency spatial parametric soliton formed by virtue of the cascade frequency tripling in quadratic, periodically poled crystals. A variational approach and a method of averaging are developed, which make it possible to describe analytically, with good accuracy, the characteristics of the spatial solitons studied numerically.     

Solitons on Tori and Soliton Crystals

Necessary conditions for a soliton on a torus \({M = \mathbb{R}^m/\Lambda}\) to be a soliton crystal, that is, a spatially periodic array of topological solitons in stable equilibrium, are derived. The stress tensor of the soliton must be L ² orthogonal to \({\mathbb{E}}\) , the space of parallel symmetric bilinear forms on TM, and, further, a certain symmetric bilinear form on \({\mathbb{E}}\) , called the hessian, must be positive. It is shown that, for baby Skyrme models, the first condition actually implies the second. It is also shown that, for any choice of period lattice Λ, there is a baby Skyrme model which supports a soliton crystal of periodicity Λ. For the three-dimensional Skyrme model, it is shown that any soliton solution on a cubic lattice which satisfies a virial constraint and is equivariant with respect to (a subgroup of) the lattice symmetries automatically satisfies both tests. This verifies, in particular, that the celebrated Skyrme crystal of Castillejo et  al., and Kugler and Shtrikman, passes both tests.     

Dynamics of the Manakov Solitons in Biased Guest-Host Photorefractive Polymer

In the biased guest-host photorefractive polymer,the Manakov equations can be used to describe the optical soliton propagation and interaction.Hereby for such equations,via the Hirota method and symbolic computation,analytic soliton solutions in the bright-dark and dark-dark forms are obtained.Based on the choice of photorefractive polymer parameter and incident-optical-beam parameter,the bright-dark and dark-dark solitons as well as their interaction can occur in the polymer when the total intensity is much lower than the background illumination,and our analysis indicates that the incident light with different polarization directions influence little on the soliton propagation.γ,representing the soliton intensity far away from the soliton center,determines the appearance of bright or dark soliton under the background illumination.Through the graphic and asymptotic analysis on the two-soliton solutions along with the different γ,we find that there exist the elastic and inelastic interactions between the bright-dark solitons,while the interactions between the dark-dark solitons are always elastic.     

Dynamics of the Manakov Solitons in Biased Guest-Host Photorefractive Polymer

In the biased guest-host photorefractive polymer, the Manakov equations can be used to describe the optical soliton propagation and interaction. Hereby for such equations, via the Hirota method and symbolic computation, analytic soliton solutions in the bright-dark and dark-dark forms are obtained. Based on the choice of photorefractive polymer parameter and incident-optical-beam parameter, the bright-dark and dark-dark solitons as well as their interaction can occur in the polymer when the total intensity is much lower than the background illumination, and our analysis indicates that the incident light with different polarization directions influence little on the soliton propagation. γ, representing the soliton intensity far away from the soliton center, determines the appearance of bright or dark soliton under the background illumination. Through the graphic and asymptotic analysis on the two-soliton solutions along with the different γ, we find that there exist the elastic and inelastic interactions between the bright-dark solitons, while the interactions between the dark-dark solitons are always elastic.     

Light-Induced Photorefractive Waveguides in Iron-Doped Lithium Niobate Crystals

Waveguides were fabricated in lithium niobate crystals solely by light irradiation using binary optical masks and SLM-prepared optical masks. Arrayed-waveguides were also obtained by once or twice irradiations of an interferogram of two plane waves.