Incoherently coupled bright-dark photovoltaic soliton pairs based on two-photon photorefractive effect

The coupling of two mutually incoherent optical beams with the same polarization and wavelength in two-photon photovoltaic photorefractive crystal is studied, it is predicted theoretically that incoherently coupled bright-dark photovoltaic spatial soliton pairs are possible due to two-photon photorefractive effect. The existing conditions of these soliton pairs in the crystal are discussed in detail. The intensity profile of these soliton pairs is shown by numerical calculation under the parameters of relevant crystal.     

Modulational instability of optical beams in photovoltaic and photorefractive media due to two-photon photorefractive effect under open circuit condition

The modulational instability of broad optical beams in two-photon photorefractive (PR) photovoltaic materials under open circuit conditions has been investigated. Under linear stability framework, the one dimensional modulational instability growth rate has been estimated by considering the space charge field. Gain of the instability is shown to exist only when the photovoltaic fields orients in the same direction with respect to the optical c-axis of the medium. It is found that the behavior of the gain spectrum is different in low and high power regions. We have found by numerical simulations that the evolution of the soliton induced by the modulational instability at low photovoltaic field show the dynamical behaviors similar to those of the localized beam as the initial profile. However, it has been shown that increasing photovoltaic fields produce traveling, breathing, and mutually interacting solitons.     

Photovoltaic spatial soliton pairs in two-photon photorefractive materials

We report the existence of incoherently coupled bright-bright steady state photovoltaic soliton pairs in two-photon photorefractive material under open circuit conditions. Based on WKBJ method and paraxial ray approximation, we have obtained coupled equations describing dynamical evolution of spatial soliton pairs. In the steady state regime, the present analysis leads to the identification of existence equation of bright-bright solitons, which captures a plethora of soliton pairs. We have undertaken linear stability analysis which shows that these solitons are stable.     

双光子光折变介质中的非相干耦合空间孤子对

对双光子光折变晶体中两束偏振方向和波长都相同的互不相干光束的耦合进行了研究, 预言了非相干耦合暗-暗、亮-亮及亮-暗双光子空间孤子对的存在. 关键词： 双光子光折变效应 光折变材料 空间孤子     

Photovoltaic solitons in two-photon photorefractive materials under open-circuit conditions

We present the evolution equation of one-dimensional spatial soliton in two-photon photorefractive media under open-circuit conditions. In the steady state regime, our solutions show that the dark and bright photovoltaic spatial solitons can be supported in two-photon photorefractive media under open-circuit conditions.     

Stability of incoherently coupled bright–dark spatial soliton pairs in biased two-photon photovoltaic photorefractive crystals

This paper investigated numerically the stability of bright–dark soliton pairs in biased two-photon photovoltaic photorefractive crystals. Our analysis indicates that these soliton pairs exist irrespective of the polarity of photovoltaic field and external bias field and they are stable only in the particular range of negative polarity. That is to say, the modulational instability emerges for the positive polarity. In range of negative polarity, there exist a characteristic value of photovoltaic field and external bias field. When the values are less than the characteristic value, these bright–dark soliton pairs are stable. If the values are large than the characteristic value, the modulational instability will still emerge.     

Incoherently coupled two component screening photovoltaic solitons in two-photon photorefractive materials under the action of external field

The existence of incoherently coupled two-component steady state photovoltaic solitons in biased two-photon photorefractive materials due to two-photon photorefractive effect has been investigated. In the steady state regime, these incoherently coupled solitons can propagate in bright–bright, dark–dark and bright–dark configurations. The most important finding is that, with the application of electric field, it is possible to generate solitons and control them in those media where soliton formation was hitherto prohibited. Dynamic evolution of these solitons has been examined using numerical simulations, which show that these solitons are stable.     

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.     

双光子光折变介质中非相干耦合亮-暗屏蔽光伏孤子对

对有外加电场的双光子光伏光折变晶体中两束偏振方向和波长都相同的互不相干光束的耦合进行研究,给出产生亮-暗双光子光折变屏蔽光伏孤子对需满足的条件.以Cu:KNSBN晶体作为研究对象,选取α=117.3,β=83.79,η=1.5×10-4,σ=104,δ=0.005,r=10时,给出双光子光折变晶体中的非相干耦合亮-暗屏蔽光伏孤子对2个孤子分量光强的空间分布,证明有外加电场的双光子光伏光折变晶体中存在非相干耦合亮-暗屏蔽光伏孤子对,指出孤子对是由偏振态和波长都相同的两束互不相干光形成的,当外加电场方向和晶体中光伏电场的方向与晶体光轴方向相同时,双光子光折变晶体中可支持亮孤子峰值光强稍大于暗孤子最大光强的非相干耦合亮-暗孤子对,当外加电场方向和晶体中光伏电场的方向与晶体光轴方向相反时,双光子光折变晶体中可支持亮孤子峰值光强稍小于暗孤子最大光强的非相干耦合亮-暗孤子对.     

亮-暗非相干耦合光伏孤子对

对开路光伏介质中两束共线传播的互不相干光束的耦合作用进行了研究，发现在光伏效应的作用下，介质中可形成亮-暗非相干耦合空间孤子对，并对这种孤子对的物理特性进行了讨论。     

Separate spatial soliton pairs in an unbiased series two-photon photorefractive crystal circuit

Dark (bright) steady-state spatial solitons are predicted in one dimension for a series circuit consisting of two two-photon photorefractive crystals of which at least one must be photovoltaic. Each crystal can support a spatial soliton. The two solitons are known collectively as separate spatial soliton pairs with three types: dark-dark, bright-dark and bright-bright. In the limit in which the optical wave has a spatial extent much less than the width of the crystal, the dark soliton can affect the other soliton by light-induced current, but the bright soliton cannot affect the other soliton in the soliton pair.     

Incoherently coupled grey-grey spatial soliton pairs due to two-photon photorefractive media

The coupling of two mutually incoherent optical beams with the same polarization and wavelength in two-photon photorefractive media is studied; it is shown that incoherently coupled grey-grey spatial soliton pairs are possible due to two-photon photorefractive effect under appropriate bias conditions. The relevant example is presented. The grey-grey spatial soliton pairs reduce to dark-dark spatial soliton pairs when the greyness is zero.     

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.     

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.     

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。     

亮-暗复色光伏孤子

提出一种实现亮-暗复色光伏孤子的方法.不共轴的两束同频率相干但反相的亮光束共同形成一中空光束，在此暗区引入另一束不同频率的亮光束.这三束光在一定条件下可以通过非线性相互作用而形成亮-暗复色孤子.通过数值分析的方法对这种亮-暗复色光伏孤子的空间动力过程进行了研究.研究表明，这种亮-暗结构具有光控光特性. 关键词： 亮-暗复色光伏空间孤子 光控光     

Incoherently coupled spatial soliton families in photorefractive polymers

It is shown theoretically that incoherently coupled bright or dark spatial soliton families can be realized in biased guest-host photorefractive polymers under steady-state conditions. These soliton families can be established provided the multiple carrier beams share the same polarization, wavelength, and are mutually incoherent. These soliton families will reduce to soliton pairs when they contain only two components. Moreover, the stability of such soliton families has been discussed by the numerical method.     

高斯光束在有外电场的双光子光伏光折变材料中的演化

为了得到一束高斯光束和两束高斯光束的相互作用在有外电场的双光子光伏光折变材料中的演化结果,将高斯光束作为入射波,采用数值方法求解波传播方程。研究结果表明:在外加电场、光强峰值分别与晶体参量匹配的情况下,一束高斯光束能演化为稳定的屏蔽光伏明孤子,而在不匹配时,一束高斯光束在传播过程中则呈现周期性压缩或膨胀现象。同时也发现:在作用距离范围内,同相位的两高斯光束相互吸引,并伴随有融合现象;而相位相反的两高斯光束相互排斥,且其排斥作用随着光束初始间距的减小而增加,当两高斯光束的相位差位于区间(0,π)和(-π,0)时,其相互作用过程中伴有能量的转移,两区间中能量转移方向相反。     

Incoherently coupled spatial soliton families in biased two-photon photorefractive crystals with both the linear and quadratic electro-optic effect

Different from the cases discussed preciously, nonlinear changes of refractive index in the photorefractive materials are influenced by both the linear and quadratic electro-optic effect simultaneously now. Here we present the evolution equations of one-dimension incoherently coupled spatial soliton families due to two-photon effect in biased photorefractive crystals with both the linear and quadratic electro-optic effect and discuss their existence conditions and properties in detail. Our analysis indicates that these soliton families can exist in all three possible realizations： dark-dark, bright-bright and dark-bright provided that the incident beams have the same polarization, wavelength and are mutually incoherent. Finally, the stabilities of these soliton families have been discussed by means of beam propagation methods.     

中心对称光折变晶体中非相干耦合空间孤子族

 为了得到中心对称光折变晶体中存在非相干耦合空间孤子族的结果,基于中心对称光折变晶体空间孤子的基本理论,推导出了中心对称光折变晶体中非相干耦合亮、暗和亮-暗混合空间孤子族空间归一化包络解的积分形式,并对其特性进行了数值模拟。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的光束耦合形成的,非相干耦合孤子族在中心对称光折变晶体中传播时,各分量成分光束都能稳定传播,当入射光束中只含有两分量时,空间孤子族退化为暗 暗、亮-亮和亮-暗空间孤子对。