含分压电阻的光折变屏蔽光伏空间灰孤子

为了研究外加偏压光伏光折变晶体中的空间灰孤子,建立了含分压电阻的光折变屏蔽光伏空间灰孤子的演化方程,给出了灰孤子解.采用数值模拟的方法,求解灰孤子的数值表达式,得到了不同参量取值下的灰孤子包络.数值结果表明：当分压电阻、晶体的外加电场和光伏场取不同值时,可以分别得到有无分压电阻的屏蔽灰孤子|开路的光伏灰孤子,有、无分压电阻的闭路光伏灰孤子|有、无分压电阻的屏蔽光伏灰孤子.     

含分压电阻的光折变屏蔽光伏空间灰孤子(英文)

为了研究外加偏压光伏光折变晶体中的空间灰孤子,建立了含分压电阻的光折变屏蔽光伏空间灰孤子的演化方程,给出了灰孤子解.采用数值模拟的方法,求解灰孤子的数值表达式,得到了不同参量取值下的灰孤子包络.数值结果表明:当分压电阻、晶体的外加电场和光伏场取不同值时,可以分别得到有无分压电阻的屏蔽灰孤子;开路的光伏灰孤子,有、无分压电阻的闭路光伏灰孤子;有、无分压电阻的屏蔽光伏灰孤子.     

一维光伏空间灰孤子及其稳定性研究

从考虑背景光的光伏作用后的光束在光伏媒质中传播的方程出发,证明了在折射率改变为正的光伏媒质中也可以形成灰孤子。光束以灰孤子状态在光伏晶体中传播时,其横向相位必须具有一个与光强分布有关的形式分布,表达式为φ（s）=v[η-∫y^-2（η）dη],其中v是灰孤子的横向运动速度,η是无量纲化坐标,y（η）是归一化的光场振幅。分别讨论了光束灰度、光强振幅、信号光与背景光的有效Glass系数之比R对一维的光伏空间灰孤子宽度、横向总相移和横向运动速度的影响,并分析了光伏灰孤子的稳定性。当光束的灰度m为0时,这一理论可直接退化为光伏暗孤子的理论。     

有偏压的光伏光折变晶体中的空间灰孤子

修正和完善了有偏压的光伏光折变晶体中空间孤子的非线性波动方程的理论.当光伏效应可忽略时,它转化为屏蔽孤子的非线性波动方程;当外电场为零时,它转化为闭路和开路光伏孤子的非线性波动方程.证明了有偏压的光伏光折变晶体中存在着空间灰孤子.它起源于对外电场的非均匀空间屏蔽和光伏效应.当光伏效应可忽略时,它转化为屏蔽灰孤子;当外电场为零闭路时,它预言了在光伏光折变晶体中存在着光伏灰孤子.     

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.     

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.     

光折变晶体中光诱导波导的折射率分布

分别讨论了亮孤子和暗孤子在光折变晶体中诱导波导的折射率分布,结果表明光诱导波导的折射率分布除与光强的倒数有关外,还与光强对数的一阶导数有关.后者对折射率的影响引起波导折射率的非对称性分布.     

双光子光折变介质中光伏空间孤子

基于双光子光折变介质中空间孤子的统一理论,采用数值模拟的方法,比较了双光子光伏光折变介质中开路光伏空间孤子、短路光伏空间孤子和闭路光伏空间孤子的特性.结果表明:双光子光伏光折变介质中,闭路暗光伏孤子所需非线性要比开路暗光伏孤子所需非线性小,同时暗光伏空间孤子的半峰全宽随着负载电阻的增加而加宽;亮光伏空间孤子的形态与负载电阻基本无关.     

单光子光折变独立灰-灰屏蔽光伏空间孤子对

提出了在两块单光子光折变晶体和一个电源通过导线串联而成的回路中存在灰-灰屏蔽光伏空间孤子对的理论.在适当的条件下,推出了在晶体回路中两光束传播的耦合方程.证明了灰-灰独立屏蔽光伏孤子对的存在.研究结果表明,孤子对中的两灰孤子通过光诱导电流而相互影响,它们的相互耦合能影响到彼此的空间包络、动态演化和稳定性.     

基于双光子光折变效应的非相干耦合灰光伏孤子族

为了研究开路条件下双光子光伏光折变材料中的灰光伏孤子族,建立了光伏孤子族的动态演化方程,给出了非相干耦合灰光伏孤子族的数值解.采用数值模拟的方法,求解孤子族的数值表达式.结果表明:这种孤子族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.当孤子族只有两个分量时,灰光伏孤子族可以退化成灰-灰光伏孤子对;当孤子的灰度...     

Waveguides induced by steady-state gray solitons in biased photorefractive-photovoltaic crystals

We carry out a theoretical investigation of the properties of waveguides induced by photorefractive one-dimensional steady-state gray spatial solitons (i.e., screening solitons, photovoltaic solitons, and screening-photovoltaic solitons). We demonstrate that waveguides induced by photorefractive steady-state gray spatial solitons are only a single guided mode for both all soliton graynesses and all values of ρ, where ρ is the ratio between the soliton peak intensity and the dark irradiance, and moreover, waveguides induced by gray photovoltaic solitons for closed-circuit condition are also only a single guided mode for all electric current densities. We find that the confined energy near the center of a photorefractive steady-state gray spatial soliton increases with ρ and decreases with an increase in the soliton grayness. We also find that the confined energy near the center of a gray photovoltaic soliton for closed-circuit condition increases with the electric current density. On the other hand, waveguides induced by gray screening-photovoltaic solitons are gray screening soliton-induced waveguides when the bulk photovoltaic effect is neglectable and are gray photovoltaic soliton-induced waveguides when the external bias field is absent.     

Waveguides Induced by Screening-Photovoltaic Solitons in Biased Photorefractive-Photovoltaic Crystals

We investigate theoretically waveguides induced by screening-photovoltaic solitons in biased photorefractive-photovoltaic crystals. We show that the number of guided modes in a waveguide induced by a bright screening photovoltaic soliton increases monotonically with the increasing intensity ratio of the soliton, which is the ratio between the peak intensity of the soliton and the dark irradiance. On the other hand, waveguides induced by dark screening-photovoltaic solitons are always single mode for all intensity ratios and the confined energy near the centre of a dark screening-photovoltaic soliton increases monotonically with the increasing intensity ratio. When the bulk photovoltaic effect is neglectable, these waveguides are those induced by screening solitons. When the external field is absent, these waveguides predict those induced by photovoltaic solitons.     

Grey screening-photovoltaic soliton-induced waveguides

This paper shows that waveguides induced by grey screening-photovoltaic solitons are always single mode for all intensity ratios, which are the ratio between the peak intensity of the soliton and the dark irradiance. It finds that the confined energy near the centre of the grey soliton and the propagation constant of the guided mode increase monotonically with increasing intensity ratio. On the other hand, when the soliton greyness increases, the confined energy near the centre of the grey soliton and the propagation constant of the guided mode reduce monotonically. When the bulk photovoltaic effect is neglected for short circuits, these waveguides become waveguides induced by grey screening solitons. When the external bias field is absent, these waveguides become waveguides induced by grey photovoltaic solitons.[第一段]     

Waveguides induced by grey screening solitons

We investigate the properties of waveguides induced by one-dimensional grey screening solitons in biased photorefractive crystals. The results show that waveguides induced by grey screening solitons are always of single mode for all intensity ratios, i.e. the ratios between the peak intensity of the soliton and the dark irradiance. Our analysis indicates that the energy confined near the centre of the grey soliton and the propagation constant of the guided mode of the waveguide induced by the grey screening soliton increase monotonically with intensity ratio increasing. On the other hand, when the soliton greyness increases, the energy confined near the centre of the grey soliton and the propagation constant of the guided mode of the waveguide induced by the grey screening soliton decrease monotonically. Relevant examples are provided where photorefractive crystal is of the strontium barium niobate type.     

开环系统中灰光伏孤子的时间及演化特性分析

分析了开环系统中一维灰光伏孤子的时间特性.基于与时间相关的演化方程,用数值方法得到了准稳态和稳态的灰孤子解,分析了形成准稳态灰孤子的物理机制.结果显示准稳态灰孤子的宽度是与光强无关的,并且它们的形成时间和孤子的峰值与背景辐射强度比成反比.这些性质与开环系统中的亮、暗孤子的性质很相似.同时采用波传播的数值解法,分析了它们的传播特性,结果显示它们在小于10％的扰动下是相对稳定的.     

开路低振幅空间光伏孤子的时间分析

理论分析了一维光折变空间孤子在低振幅开路条件下的传输特性和强度宽度的演化特性.研究表明,开始阶段所形成的强度宽度较宽的孤子, 其宽度随着时间演化单调递减到一个最小值,直到稳态形成;对于不同的孤子峰值强度与暗辐射比值,整个过程所需要的时间接近于无照明场时介质的介电驰豫时间.在时间趋于无穷的情况下,系统趋于稳定,得到了暗孤子和亮孤子的解析解.     

Temporal behavior of dark spatial solitons in closed-circuit photovoltaic media

We show that the time-dependent nonlinear wave equation in closed-circuit photovoltaic media can exhibit quasi-steady-state and steady-state spatial solitons. We demonstrate that the formation time of open-circuit quasi-steady-state and open-circuit steady-state dark solitons decreases with an increase in the intensity ratio of the soliton, which is the ratio between the soliton peak intensity and the dark irradiance. We find that for the time-dependent nonlinear wave equation that exhibits only an open-circuit steady-state dark soliton, changing the electric current density J₀ does not generate quasi-steady-state dark solitons and affects the formation time of steady-state dark solitons and that for the time-dependent nonlinear wave equation that exhibits an open-circuit quasi-steady-state dark soliton, changing J₀ gives rise to three different time evolution regimes of the full width half maximum of the soliton’s intensity. The first regime shows that the formation time of steady-state dark solitons increases with J₀ whereas the formation time of quasi-steady-state dark solitons is independent of J₀. The second regime shows that the formation time of steady-state dark solitons decreases with an increases in J₀ and the formation time of quasi-steady-state dark solitons increases with J₀. The third regime shows that changing J₀ enables only steady-state dark solitons in the time-dependent nonlinear wave equation, of which the formation time increases with J₀.     

Temporal development of open-circuit bright photovoltaic solitons

This paper investigates the temporal behaviour of open-circuit bright photovoltaic spatial solitons by using numerical techniques. It shows that when the intensity ratio of the soliton, the ratio between the soliton peak intensity and the dark irradiance, is small, the quasi-steady-state soliton width decreases monotonically with the increase of τ-, where τ- is the parameter correlated with the time, that when the intensity ratio of the soliton is big, the quasi-steady-state soliton width decreases with the increase of τ- and then increases with τ, and that the formation time of the steady-state solitons is not correlated with the intensity ratio of the soliton. It finds that the local nonlinear effect increases with the photovoltaic field, which behaves as that the width of soliton beams is small and the self-focusing quasi-period is short. On the other hand, we also discuss that both the time and the temperature have an effect on the beam bending.     

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     

Solitons in photovoltaic photorefractive media with an external electric field

We use the classical Lie-group method for studying the evolution equation in photovoltaic photorefractive media with an external electric field, reducing it to some similarity equations firstly, and then obtain some exact analytical solutions including the soliton solution, the period solution and the oscillatory solution. We also obtain the bright soliton, dark soliton, gray soliton from these similarity equations with the numerical method. Furthermore, we investigate what factors contribute to the beamwidth of these solitons with the numerical method and know the beamwidth of these solitons are associated with the external electric field, the photovoltaic field and the intensity ratio of the incident soliton.