Intermediate regime of light diffraction by surface ultrasonic waves in planar gyrotropic optical waveguides

The intermediate regime of optoacoustic interaction, similar to the Bragg one, with Rayleigh surface ultrasonic waves in gyrotropic planar waveguides is studied. A system of equations of bound waves is presented that describes planar optoacoustic interaction in the intermediate, Raman-Natoh, and Bragg regimes of light diffraction by surface ultrasonic waves. It is shown that the optical activity of a wavequide film favors the incident light energy pumping to diffracted light for a TE-polarization wave and decelerates this process for an incident TM-polarization wave. Mozyr' State Pedagogical Institute, 28, Studencheskaya St., Mozyr', 247760, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 3, pp. 412–416, May–June, 1997.     

Bragg diffraction of light by a hypersound in gyrotropic cubic crystals

Noncollinear acousto-optical interaction of light beams in acoustically gyrotropic cubic crystals is considered. The dependences of the diffraction efficiency of the parameters of the optical and acoustical gyrotropy have been established. The attainability of the optimal efficiency of diffraction by shear ultrasonic waves due to the anisotropy electrically induced by the external field under conditions of longitudinal electro-optical effect is shown.__________Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 1, pp. 80–84, January–February, 2005.     

Diffraction of light by ultrasound in paratellurite crystals under Fresnel reflection conditions

We show that layers of acousto-optic gyrotropic paratellurite crystals perturbed by ultrasound can be used as efficient light modulators in transmission and reflection mode. We have established that the relative intensities of the diffracted waves are determined by the ratio of the refractive indices of the bounding media, the intensity of the ultrasound, and the thickness of the modulated layer. We show that for an asymmetric diffraction structure, efficient acousto-optic conversion is possible in reflection mode, and the weak effect of the gyrotropy is due to its suppression by Fresnel reflection at the boundaries of the layer. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 819–823, November–December, 2006.     

Polarization-Independent Ultrasonic Modulation of Light in Gyrotropic Cubic Bismuth Germanate Crystals

An intermediate regime of light diffraction by ultrasound propagating along the [001] and [110] axes of a gyrotropic cubic bismuth germanate crystal is investigated. The possibility of polarization-independent light modulation in the intermediate regime of diffraction close to the Bragg regime is shown. The dependences of the diffraction efficiency on the incident light polarization azimuth at different ultrasonic wave intensities are given.     

有限宽平板波导中的克尔空间孤子及全光器件的设计

利用数值模拟的方法研究了倾斜入射的傍轴光束在有限宽非线性平板波导内的传输规律.研究发现,当不同波长相同束宽的光束各以临界功率倾斜入射波导时,如果倾斜角、入射点都一样,它们将沿大致相同的周期性的Z字形路径传输;如果光束功率进一步增大,相邻反射点之间的间距随传输距离有逐渐变大的趋势,Z字形路径不再有严格的周期性;当功率相当大时,光束将沿波导z方向传输,不再在波导的两个边界之间来回反射.利用倾斜入射光束在波导内的传输路径随功率而变的特点,设计了一个功率开关和一个光时分解复用器. 关键词： 空间光孤子 有限宽非线性平板波导 全光器件     

Rigorous analysis of optical forces between two dielectric planar waveguides immersed in dielectric fluid media

This work presents a rigorous analysis of optical forces between planar waveguides immersed in an arbitrary background medium. This approach exploits the Minkowski stress tensor formulation, which is compared with a normalized version of the dispersion relation method, showing excellent results agreement for different dielectric fluid media. Due to slot‐waveguide effect, optical forces from TM modes are more sensitive to changes in the fluid refractive index than the TE counterparts. Furthermore, the repulsive optical force from the antisymmetric TM1 mode becomes stronger for higher refractive indexes, whereas the attractive force of the symmetric TM0 mode becomes weaker. The methodology and results presented in this work provide a rigorous analysis of nano‐optomechanical devices actuated by optical forces in a broad range of materials and applications. Therefore, this study may impact areas of light‐induced interactions presenting novel optofluidic and optomechanical functionalities, thus finding applications in nanoscale transport, sensing and manipulation.

     

任意坐标系下非圆正规光波导的一般解及应用

给出了任意坐标系下非圆正规光纤随传输距离z指数变化的一般解，它具有exp｛i(+ΔβV)z｝E0(x,y)的形式，而V是由主轴偏角θ惟一确定的矩阵，称为主轴矩阵.还给出了相应的亥姆霍兹方程，并应用于研究有微小变形的二层弱导非圆光纤，和解释光纤纵向不均匀性对双折射的抑制效应. 关键词： 非圆正规光纤 偏振主轴 偏振模色散(PMD)     

光脉冲在微环耦合谐振光波导中传输线性特性的数值仿真

利用传输矩阵法得到了微环耦合谐振光波导色散关系的一般表达式,并由色散关系出发讨论了光脉冲在微环耦合谐振光波导中传输时的线性特性,包括带宽、群速度、色散和线性相位变化,这些特性对微环耦合谐振光波导在光通信和光传感领域的应用有重要意义. 关键词： 微环光波导 光脉冲线性特性 传输矩阵法 数值仿真     

Pixel size and pitch measurements of liquid crystal spatial light modulator by optical diffraction

We present a simple technique for the determination of pixel size and pitch of liquid crystal (LC) based spatial light modulator (SLM). The proposed method is based on optical diffraction from pixelated LC panel that has been modeled as a two-dimensional array of rectangular apertures. A novel yet simple, two-plane measurement technique is implemented to circumvent the difficulty in absolute distance measurement. Experimental results are presented for electrically addressed twisted nematic LC-SLM removed from the display projector.     

会聚激光扫描铌酸锂晶体写入光波导时的最佳曝光间距

对利用激光精细加工技术在铌酸锂(LiNbO₃)晶体中写入光波导时的最佳曝光间距进行了详细地理论分析和实验研究.通过数值求解简化后的光折变动力学方程组，对会聚激光束沿不同方向扫描晶体时的最佳曝光间距进行了详细的数值模拟.结果表明：最佳曝光间距的选取与写入光束的扫描方向无关；当聚焦激光束平行于光轴扫描晶体时，得不到波导结构，但可以采用“三明治”辐照方式得到对称的折射率分布.采用会聚的绿激光束扫描掺铁铌酸锂(LiNbO₃：Fe)晶体进行了实验研究，晶体中的光致折射率变 关键词： 激光精细加工 最佳曝光间距 光波导 3晶体')" href="#">LiNbO₃晶体     

LiNbO3:Fe晶体中光写入波导时折射率的变化规律

研究了利用光辐照法制作光折变波导时LiNbO3:Fe晶体中折射率变化的规律.分别采用波长为6328nm和532nm的寻常偏振和非常偏振的细激光束和片状激光束，在LiNbO3:Fe晶体中进行了写入波导实验.研究表明，制作波导的写入光宜采用寻常偏振光.在利用由光束辐照LiNbO3:Fe晶体形成的正折射率变化区域作为波导结构时，必须严格控制辐照时间.否则，由于长时间光辐照会带来较强的噪音栅以及折射率变化区域会发生扩展，而难以形成优 质波导.利用片光在“三明治”方式辐照下，以小曝光量制作波导时，可以避免噪音栅的 关键词： 光致折射率变化 光折变波导 光辐照法 LiNbO3:Fe晶体     

Influence of external electric and magnetic fields on magnetoelectric interaction in ferromagnets

A gap in the spectrum of spin and ferroelectric waves is investigated versus magnetic and electric fields. It is demonstrated that the magnetoelectric interaction is amplified with increasing external magnetic field and is weakened with increasing external electric field. This allows the interaction between the spin and ferroelectric subsystems to be controlled by external fields. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 2, pp. 43–47, February, 2009.     

Influence of parameters on light propagation dynamics in optically induced planar waveguide arrays

The diffraction and refraction of light beam in optical periodic structures can be determined by the photonic band-gap structures of spatial frequency. In this paper, by employing the equation governing the nonlinear light propagations in photorefractive crystals, we study the photonic band-gap structures, Bloch modes, and light transmission properties of optically induced planar waveguide arrays. The relationship between the photonic band-gap structures and the light diffraction characteristics is discussed in detail. Then the influence of the parameters of planar waveguide arrays on the band-gaps structures, Bloch modes, and linear light transmissions is analyzed. It is revealed that the linear light transmission properties of waveguide arrays are tightly related to the diffraction relationships determined by band-gap structures. And the Bloch modes corresponding to different transmission bands can be excited by different excitation schemes. Both the increases of the intensity and the period of the array writing beam will lead to the broadening of the forbidden gaps and the concentration of the energy of the Bloch modes to the high-index regions. Furthermore, the broadening of the forbidden gaps will lead to separation and transition between the Bloch modes of neighboring bands around the Bragg angle. Additionally, with the increase of the intensity of the array writing beams, the influences from light intensity will tend to be steady due to the saturation of the photorefractive effect. Supported by the Youth for Northwestern Polytechnical University (NPU) Teachers Scientific and Technological Innovation Foundation, the NPU Foundation for Fundamental Research, and the Doctorate Foundation of NPU (Grant No. CX200514)     

金属纳米结构表面吸附的CO分子在外电场中的相互作用

建立金属纳米颗粒在外电场中的排列结构模型，用经典理论分析纳米结构金属表面上吸附的CO分子在外电场中的相互作用能，包括有效偶极子间的相互作用和与局域电场的相互作用，并讨论和计算了纳米颗粒表面附近的局域电场. 用Monte-Carlo方法进行数值计算和模拟，具体给出纳米颗粒表面CO分子的分布和相互作用能，表明金属表面纳米结构使CO产生凝聚，并使分子相互作用能增加，为解释异常红外吸收效应提供依据. 关键词： 纳米结构金属 吸附分子 相互作用 局域电场     

Generation of electromagnetic waves in the terahertz frequency range by optical rectification of a Gaussian laser pulse in a plasma in presence of an externally applied static electric field

We propose a theoretical model for the generation of electromagnetic waves in the terahertz (THz) frequency range by the optical rectification of a Gaussian laser pulse in a plasma with an applied static electric field transverse to the direction of propagation. A Gaussian laser pulse can exert a transverse component of the quasi‐static ponderomotive force on the electrons at a frequency in the THz range by a suitable choice of the laser pulse width. This nonlinear force is responsible for the density oscillation. The coupling of this oscillation with the drift velocity acquired by electrons due to the applied static electric field leads to the generation of a nonlinear current density. A spatial Gaussian intensity profile of the laser beam enhances the generated THz yield by many folds as compared to a uniform spatial intensity profile.     

The quartic oscillator in an external field and the statistical physics of highly anisotropic solids

The statistical mechanics of one- and two-dimensional Ginzburg–Landau systems is evaluated analytically, via the transfer matrix method, using an expression of the ground state energy of the quartic anharmonic oscillator in an external field. In the two-dimensional case, the critical temperature of the order–disorder phase transition is expressed as a Lambert function of the inverse inter-chain coupling constant.     

（BaSr）TiO3晶体光诱导自泵浦位相共轭的实验研究

对（ＢａＳｒ）ＴｉＯ３晶体中光诱导自泵浦位相共轭现象进行了实验研究。发现诱导自泵浦的输出特性取决于诱导光束强度和信号光的入射条件，并在一定条件下呈现双稳性．作者认为，这是由于诱导光束改变晶体中信号光束Ｆａｎｎｉｎｇ散射强度分布的结果。     

Modulation of terahertz generation in dual-color filaments by an external electric field and preformed plasma

Terahertz generation driven by dual-color filaments in air is demonstrated to be remarkably enhanced by applying an external electric field to the filaments. As terahertz generation is sensitive to the dual-color phase difference, a preformed plasma is verified efficiently in modulating terahertz radiation from linear to elliptical polarization. In the presence of preformed plasma, a dual-color filament generates terahertz pulses of elliptical polarization and the corresponding ellipse rotates regularly with the change of the preformed plasma density. The observed terahertz modulation with the external electric field and the preformed plasma provides a simple way to estimate the plasma density and evaluate the photocurrent dynamics of the dual-color filaments. It provides further experimental evidence of the photo-current model in governing the dual-color filament driven terahertz generation processes.     

Influence of spin-orbit coupling induced by in-plane external electric field on the intrinsic spin-Hall effect in a Rashba two-dimensional electron gas

We study theoretically the influence of spin--orbit coupling induced by in-plane external electric field on the intrinsic spin-Hall effect in a two-dimensional electron gas with Rashba spin--orbit coupling. We show that, after such an influence is taken into account, the static intrinsic spin-Hall effect can be stabilized in a disordered Rashba two-dimensional electron gas, and the static intrinsic spin-Hall conductivity shall exhibit some interesting characteristics as conceived in some original theoretical proposals.