在金属与光折变晶体界面形成的表面波研究

应用质点振荡模型和数值模拟方法研究了在金属与光折变晶体界面形成表面波的条件及其能量变化. 结果表明: 传播常数的正负影响表面波的类型及波能量分布, 当传播常数取负值时在界面处形成非局域表面波, 取正值时在界面处形成振荡表面波和局域表面波, 局域表面波的能量随传播常数的变大而单调递增. 在一给定的物理系统中, 可通过调节决定非线性效应强度的可变参量控制不同阶数局域表面波模及其传播波形.     

线性电介质和中心对称光折变晶体界面表面波的研究

报道了中心对称光折变晶体与线性电介质界面表面波的形成及能量变化. 通过调节传播常数和波导参数的方法,可以得到非局域、振荡、局域三种类型的表面波. 波导参数和传播常数之差大于阈值时,线性电介质和中心对称光折变晶体界面可以形成局域表面波. 波导参数为正值时,局域表面波主要聚集在中心对称光折变晶体内,随着传播常数的增大,波能量随之单调递增,表面波可以稳定传播. 在给定的条件下,调节决定非线性作用强度的可变参量可以控制局域表面波模的阶数和传播波形. 关键词： 非线性光学 中心对称光折变晶体 表面波     

Nonlinear Surface Waves at the Interface between Optical Media with Different Nonlinearity Induction Mechanisms

Journal of Experimental and Theoretical Physics - Different types of nonlinear surface waves with a peculiar polarization, which emerge at the interface between a photorefractive crystal and a...     

Surface Waves at the Interface of a Photorefractive Crystal and a Medium with Positive Kerr Nonlinearity

Physics of the Solid State - The types of nonlinear surface waves with extraordinary polarization arising at the interface between a photorefractive crystal and a medium with positive Kerr...     

Polymeric photorefractive surface waves

We theoretically studied photorefractive surface waves supported by polymers with orientationally enhanced photorefractive effect. We find that the orientational enhancement and the dependency of the quantum efficiency of generating mobile holes on the electric field make the diffusion nonlinearity in photorefractive polymers dependent not on only the variation of light intensity but also on external electric field, which is very different from the external electric field independent diffusion nonlinearity in inorganic photorefractive crystals. Consequently the profile, frequency and especially the penetration depth of polymeric photorefractive surface waves strongly depend on external electric field, which makes it more controllable than that in photorefractive inorganic crystals. The stability of polymeric photorefractive surface waves, the effects of birefringence component and electro-optic component of orientationally enhanced photorefractive nonlinearity on the formation of x or y-polarized polymeric photorefractive surface waves are also discussed.     

Photorefractive line waves

We study self-channeling of light waves in a rotated cut of crystals of the 4mm and the 6mm classes, whose dominant mechanism is photorefractive diffusion nonlinearity. The existence of photorefractive line waves that can be guided along the edge of the crystal is suggested and analyzed.     

Oval-Shaped Spectrogram Formed by Randomly Oriented Refractive Index Gratings in Photorefractive Crystals

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Self-deflection of laser beams during holographic recording in photorefractive crystals

We have observed dynamic deflection of laser beams reflected from a crystal surface during recording of dynamic holograms in a photorefractive crystal. A theory describing the principal experimental facts is presented. The model takes into account the nonlinear interaction of space-charge waves. Pis’ma Zh. éksp. Teor. Fiz. 70, No. 4, 253–256 (25 August 1999)     

光折变表面波诱导的薄层波导中的导波模式

利用数值模拟对扩散非线性机制下由光折变表面波诱导的薄层波导中导模的形成和特点进行了研究。采用分布傅里叶法对导模的传输特性进行了模拟。通过求解本征方程,对光折变表面波诱导的薄层波导中存在的导波模式进行了数值求解。通过调节传播常数和波导参数的方法,可以控制导模的阶数和传播波形。随着阶数的增加,导模轮廓的对称性越来越差;随着波导参数的增加,导模的峰值振幅单调递增。导模的能量主要聚集在晶体薄层波导中靠近-c轴的一侧,随着传播常数的增大,导模能量先减小后增大,且导模可以稳定传播。     

Double phase conjugation with orthogonally polarized beams in a BaTiO(3) crystal

We have demonstrated experimentally the simultaneous self-conjugation of extraordinarily and ordinarily polarized light waves (lambda=514 nm), with the polarization state preserved, in a Ce:BaTiO(3) crystal. Conjugate o waves originate from coupling between o and e waves by means of a circular photogalvanic effect. The conjugator also takes advantage of the Ce:BaTiO(3) crystal, for which it is easy to generate an extraordinary conjugate beam by photorefractive backscattering. This beam of light is necessary for double phase conjugation.     

Mutually pumped phase conjugate mirror using cross polarized photorefractive coupling

This paper presents a new proposal for a mutually pumped phase conjugate mirror (MPPCM) using cross polarization. In the cross polarized MPPCM, two light beams, whose polarizations are orthogonal to each other, incident on a photorefractive crystal, causing photorefractive interaction to generate phase conjugate waves with an orthogonal polarization to an incident beam. The use of Ar⁺ laser and BaTiO₃ crystal in an experiment for the cross polarized MPPCM found that diffraction efficiency for an extraordinary beam is about 20%. As opposed to a conventional parallel polarized MPPCM in which the use of a beam splitter is required to separate a diffraction beam, the cross polarized MPPCM can efficiently extract phase conjugate waves by means of a polarized beam splitter, demonstrating the advantage of substantially improved efficiency.     

Structure of elastic and electric fields induced near the boundary of a LiNbO3 crystal in the course of recording of photorefractive gratings through the photovoltaic mechanism

This paper reports on the results of the investigation into the structure of elastic and electric fields induced near the boundary of the X cut of a lithium niobate crystal during the formation of a photorefractive grating with a wave vector K parallel to the threefold symmetry axis due to the photovoltaic effect. The elastic and electric fields induced by the photorefractive grating and the changes in the components of the dielectric impermeability tensor of the lithium niobate crystal at the frequency of the light wave are calculated using numerical analysis. It is demonstrated that light waves with orthogonal polarizations can effectively interact at a photorefractive grating formed near the electrically short-circuited boundary of a lithium niobate crystal.     

Radiationless traveling waves in saturable nonlinear Schrödinger lattices

The long-standing problem of moving discrete solitary waves in nonlinear Schr?dinger lattices is revisited. The context is photorefractive crystal lattices with saturable nonlinearity whose grand-canonical energy barrier vanishes for isolated coupling strength values. Genuinely localized traveling waves are computed as a function of the system parameters for the first time. The relevant solutions exist only for finite velocities.     

Adaptive Correlation Filter Based on Dynamic Reflection Hologram Formed in Photorefractive Bi12TiO20 Crystal

An experimental and theoretical study of adaptive processing of non-stationary speckled waves by a dynamic reflection holographic grating formed in photorefractive (100) cut BTO crystal without applying external electrical field is presented.     

Photorefractive surface waves in a thin Bi12TiO20 crystal

A theoretical model considering total internal reflections of fanned beams from the side crystal surfaces and their coupling with the pump beam is proposed. The interaction of these beams results in the light intensity redistribution and in the generation of the photorefractive surface wave. An experimental observation of the light intensity self-concentration near the surface of a thin photorefractive Bi₁₂TiO₂₀ crystal is reported. It results in an acceleration of the photorefractive energy exchange process.     

球面波条件下体全息存储的衍射特性分析

从理论上推导了球面波作为参考光和读出光时体全息存储的相对衍射效率和晶体旋转角度之间的关系,对得到的衍射效率的理论公式进行了数值模拟,并且对模拟的结果进行了分析。结果表明,球面波系统的存储容量更高,角度选择性更好,并且有利于系统的小型化。     

Near-field optical study of photorefractive surface waves in BaTiO(3)

Near-field optical microscopy has been used to study photorefractive surface waves in BaTiO(3). The field distribution of the photorefractive surface wave near the crystal-air interface has been measured and compared with theory. Experimental data indicate that a micrometer-wide transition layer with dielectric and photorefractive properties that are different from the properties of the bulk BaTiO(3) exists near the interface.     

Instability of moving gratings in photorefractive crystals

It is shown that a moving intensity grating in a photorefractive crystal with a sufficiently large lifetimemobility product can give rise to an instability against excitation of weakly damped space-charge waves. Increments and threshold of the instability are investigated for the threedimensional case. Subharmonics and other nonlinear scenarios of saturation are discussed.     

Spinning-top dynamics of photorefractive grating

The photorefractive grating generated by two coupled waves produces a rich spatiotemporal dynamics such as those of solitons and chaos. In this paper, the dynamics of grating along with the slow-varying envelope of two coupled waves is studied where the photorefractive-coupling constant is large or more importantly the dynamics is much faster than the photorefractive response time of the material. Under this condition, new solutions of the dynamic grating equations are presented and analytically solved in the form of the Jacobi’s Elliptic functions. The spatiotemporal grating can result in a periodic space-charge field which in turn generates the space charge waves in the periodic case as a result of the spatiotemporal dynamics of the anisotropic two-wave mixing process. The theoretical work of the limiting case is in good agreement with the experimental results using a BaTiO₃ crystal.     

体全息存储系统中光折变晶体动态范围的理论研究

基于晶体中线性偏振波的耦合波理论以及光折变效应的能带传输模型，求出了体全息存储系统中光折变晶体动态范围的解析表达式。以ＬｉＮｂＯ３：Ｆｅ和ＢａＴｉＯ３晶体为例，讨论了读写光束与晶体作用的几何结构形式，晶体掺杂量大小及其氧化还原状态等因素对动态范围的影响。研究发现，对两种晶体来说，掺杂浓度越大，氧化程度越深，则可获得的动态范围越大。