Acousto-Optic Deflector with a High Diffraction Efficiency and Wide Angular Scanning Range

A new acousto-optic deflector with a wide angular scanning range and a high diffraction efficiency has been studied. The device uses an additional deflector, which allows the angle of incidence of the input beam to be adjusted in order to fulfill the Bragg phase–matching condition over the entire scanning range of the main deflector. The characteristics of an anisotropic two-crystal deflector based on paratellurite crystals have been measured. It has been established experimentally that the operating bandwidth of the device is 32 MHz for a diffraction coefficient no less than 90%, which determines a light beam scanning angle of 50 mrad.     

Light Diffraction on Ultrasound in a Spatially Periodic Acoustic Field

Optics and Spectroscopy - Characteristic features of anisotropic light diffraction in a spatially periodic acoustic field created by a sectioned piezoelectric transducer with antiphase excitation...     

Acousto-Optic Diffraction in an Ultrasonic Field of a Width-Profiled Transducer

Acoustical Physics - Acousto-optical diffraction in an ultrasonic field of a slow acoustic mode in paratellurite excited by a hexagonal-shaped piezoelectric transducer has been simulated in a...     

Peculiarities of Forming a Multiband Transmission Function Based on Multifrequency Acousto-Optic Diffraction

An analytical solution for the transmission function of noncoherent wideband radiation is obtained under acousto-optic (AO) filtering using a discrete set of monochromatic AO waves with a small spectral overlap. We studied characteristics of the AO transformation of a continuous spectrum of noncoherent radiation into a given set of discrete narrow bands of spectral transmission by excitation of a discrete set of sound frequencies. We carried out the analysis of transmission functions of individual channels taking into account a partial overlap of their spectra and possible intermodulation distortions. It is shown that a stationary value of the root-mean-square light power is found at the electronic output due to the photoelectric transformation and detecting diffracted light. Based on this, a necessary stationary, multiband, and nearly equidistant transmission function of a device can be formed by using a relevant spectrum of acoustic excitation. Peculiarities of this way of forming the multiband transmission function are revealed: the limitation of diffraction efficiency for an individual channel, the possibility of decoupling side lobes of adjacent channels, etc. A multiband acousto-optic filter (MAOF) was simulated that was based on a paratellurite monocrystal (TeO₂), which was previously used for experimental optical encoding. The theoretical and experimental results are in gratifying agreement.     

Trajectory-Based Interpretation of Laser Light Diffraction by a Sharp Edge

In the diffraction pattern produced by a half-plane sharp edge when it obstructs the passage of a laser beam, two characteristic regions are noticeable. There is a central region, where the diffraction of laser light appears in the region of geometric shadow, while intensity oscillations are observed in the non-obstructed area. On both sides of the edge, there are also very long light traces along the normal to the edge of the obstacle. The theoretical explanation of this phenomenon is based on the Fresnel–Kirchhoff diffraction theory applied to the Gaussian beam propagation behind the obstacle. In this paper, we supplement this explanation by considering electromagnetic flow lines, which provide a more complete interpretation of the phenomenon in terms of electric and magnetic fields and flux lines; at the same time, that can be related to average photon paths.     

Acoustic Pulse Diffraction by a Sphere in a Planar Layered Waveguide with a Gradient Layer

Consideration of the vertical sound velocity profile is highly important for solving problems of sound propagation in waveguides and scattering problems. A pulsed echo signal reflected from a spherical scatterer in a waveguide is modeled for the case of a waveguide characterized by sound velocity increasing with depth. The simplest model of the medium is considered in which the scatterer, the source, and the receiver are positioned in a layer with constant sound velocity. Below this layer, the sound velocity increases with depth so that the square of refractive index varies according to linear law. The scattering coefficients for the sphere are calculated using the normal wave method. The number of normal waves forming the echo signal is determined by the preset directionality of the source. Modeling is performed in a frequency band of 70?90 kHz for distances between the scatterer and the transmitter-receiver within 500?1000 m. The transmitted signal has the form of a pulse with cosine envelope and central frequency of 80 kHz.     

Dynamic Light Diffraction by Holographic Gratings in Photopolymeric Materials

A theoretical model of light diffraction by tilted holographic gratings in photopolymeric materials in the nonstationary regime of reading, which describes the dynamic process of optical hologram amplification with allowance for the photopolymerization and diffusion mechanisms of recording, is developed. For the given model, the dynamics of the diffraction efficiency and selective properties of hologram reading are modeled numerically when Bragg's conditions are satisfied and violated. It is demonstrated that the diffraction characteristics of tilted holograms are spatially noninvariant for the reading beam direction. The optimal conditions of reading of tilted holograms are established.     

On Dynamical X-Ray Diffraction in Crystals Modulated by an Acoustic Wave

JETP Letters - Dynamical X ray scattering in crystals modulated by an acoustic wave has been consistently considered. Diffraction in the cases of a spatially uniform amplitude of ultrasound in the...     

集成光学TM模偏振器的制作

用扩钛和质子交换相结合的方法在ｘ切ｙ传ＬｉＢｎＯ３衬底上制成了ＴＭ模集成光波导偏振器。质子交换区位于扩钛波导的末端两侧。在质子交换区域Δｎｅ〉０，Δｎ０〈０，因此ＴＥ模辐射进入衬底。偏振器工作于１．３μｍ波长，消光比优于４７ｄＢ，光纤０－波导－光纤插入损耗３．５ｄＢ。     

水基磁性液体的场诱导光衍射特性的研究

设计了一套用于研究磁性液体的场诱导静态和动态光衍射特性的实验装置.通过在样品的后方放置一个适当孔径的光阑,实现了定量研究其衍射特性的目的.采用沿衍射方向移动光阑的方法定量地研究了衍射光的空间分布.设计了一个指数衰减函数用来拟合动态衍射实验的数据,获得动态衍射的特征时间.以两种不同浓度的表面包覆型水基氧化铁磁性液体样品为例,定量地实验研究了其场诱导光衍射特性与外磁场强度和样品浓度的关系.结果表明,磁性液体的场诱导结构对光的静态和动态衍射与外磁场的强度和磁性液体的浓度有关.其静态衍射与外磁场强度呈非单调的关系;其动态衍射的特征时间与外磁场的强度成反比,与磁性液体的浓度成正比.对实验中观察到的场诱导静态和动态衍射特性的物理机理进行了详细的分析.     

水基磁性液体的场诱导光衍射特性的研究

设计了一套用于研究磁性液体的场诱导静态和动态光衍射特性的实验装置.通过在样品的后方放置一个适当孔径的光阑,实现了定量研究其衍射特性的目的.采用沿衍射方向移动光阑的方法定量地研究了衍射光的空间分布.设计了一个指数衰减函数用来拟合动态衍射实验的数据,获得动态衍射的特征时间.以两种不同浓度的表面包覆型水基氧化铁磁性液体样品为例,定量地实验研究了其场诱导光衍射特性与外磁场强度和样品浓度的关系.结果表明,磁性液体的场诱导结构对光的静态和动态衍射与外磁场的强度和磁性液体的浓度有关.其静态衍射与外磁场强度呈非单调的关系|其动态衍射的特征时间与外磁场的强度成反比,与磁性液体的浓度成正比.对实验中观察到的场诱导静态和动态衍射特性的物理机理进行了详细的分析.     

In-Situ Characterization of Three-Dimensional Optical Matters by Light Diffraction

Three-dimensional optical matters are created by combining the single beam optical trapping with the conventional Z-scan technique. Dynamic light diffraction is employed to evaluate the structure and quality of the optical matter formed at the optimum trapping power. The lattice constant of the optical matter is extracted based on the Bragg and Snell laws, showing that polystyrene spheres are nearly close-packed in the optical matter, confirmed by comparing the diffraction pattern of the optical matter with that of a colloidal photonic crystal fabricated by the self-assembled technique. The relatively broad diffraction peaks observed in the optical matter indicate that the density of disorders in it is higher than that in the photonic crystal. It is suggested that the optical matter possesses a random close-packed structure rather than a face centered cubic one.Three-dimensional optical matters are created by combining the single beam optical trapping with the conven- tional Z-scan technique. Dynamic light diffraction is employed to evaluate the structure and quality of the optical matter formed at the optimum trapping power. The lattice constant of the optical matter is extracted based on the Bragg and Snell laws, showing that polystyrene spheres are nearly close-packed in the optical matter, confirmed by comparing the diffraction pattern of the optical matter with that of a colloidal photonic crystal fabricated by the self-assembled technique. The relatively broad diffraction peaks observed in the optical matter indicate that the density of disorders in it is higher than that in the photonic crystal. It is suggested that the optical matter possesses a random close-packed structure rather than a face centered cubic one.     

Diffraction of a Guided Mode of a Dielectric Waveguide

Using the finite-difference time-domain method, we solve the problem of diffraction of a guided mode of a planar dielectric waveguide by an arbitrary-shaped body. Particular results are obtained for the scatterers in the form of isolated circular and elliptic cylinders and metal strips. We calculate the reflection and transmission coefficients of the mode along with the field structure in the near zone. Comparison with the results obtained by expansion in terms of plane waves is performed for a test problem of diffraction of the mode by a circular metal cylinder.     

Polarization Features of Diffraction of Light by Reflective Holographic Phase Gratings in a Plane-Parallel Layer

Journal of Applied Spectroscopy - The diffraction of light by reflective holographic gratings in a layer placed between the coating and the substrate having refractive indices different from the...     

“声光衍射与液体中声速的测定”实验改进探析

本文在分析"声光衍射与液体中声速的测定"实验原理的基础上,提出了实验改进方法,组装了一套简单可行的测量衍射光斑中心位置的实验装置,减小了传统实验方法中测量光斑间距的误差,提高了实验精度。     

部分相干光照明下光栅的塔尔博特效应

首先利用部分相干光理论详细地分析了在部分相干光照明下光栅的菲涅耳衍射,给出了观察面上衍射光强分布的一般公式,并就光源的发光面积对光栅塔尔博特效应的影响进行了讨论,得到了光栅衍射光强的分布随着照明光源的发光尺寸的增加而逐渐变得平滑这一结论．并且,当光源发光尺寸增加到毫米量级时,光栅的塔尔博特效应将完全消失。在实验上埘不同发光尺寸的扩展作相干光源照明光栅时的菲涅耳衍射光强进行了测量,实验结果与理论分析得出的结论相符合。     

聚合物光子晶体波导中慢光传输的电光动态调制

全光缓存器是未来全光网络中不可或缺的关键器件.针对可控光延迟和光存储的应用需求,研究了光子晶体波导中慢光传输的外部动态调制.设计了一种新型的聚合物光子晶体波导结构.用平面波展开法仿真得到该波导结构带隙中存在单一的TE导模,导模带边处的群速度可达10-2c.由于基底聚合物材料具有高电光系数和瞬态的电光响应时间,且导模慢光传输产生的电磁场局域对电光效应有增强作用.可在低涮制电压的条件下实现对慢光导模的大范围动态调制.数值分析得到在外加调制电压为80 V时导模带边波长的移动幅度达80.8 nm.慢光导模的移动随调制电压的变化基本呈线性关系,且调制的灵敏度约为1 nm/V.这种线性的外部动态调制基本可满足全光网络对慢光光缓存的需求.     

Slow Light in One-Dimensional Coupled-Resonator Waveguide Controlling by an Electric Field

The photon transport properties in one-dimensional coupled-resonator waveguide embedded with a quantum dot molecule are investigated. The calculations reveal that one can control the photon transport by using a gate electric field. The phase shift and group velocity delay of the transmitted single photon are discussed. This research may be found applications in integrated optoelectronic devices and solid quantum devices.     

Slow Light in One-Dimensional Coupled-Resonator Waveguide Controlling by an Electric Field

The photon transport properties in one-dimensional coupled-resonator waveguide embedded with a quantum dot molecule are investigated. The calculations reveal that one can control the photon transport by using a gate electric field. The phase shift and group velocity delay of the transmitted single photon are discussed. This research may be found applications in integrated optoelectronic devices and solid quantum devices.