多维正常声电光效应最佳工作模式的确定

通过对四方、立方晶系的纵向电光效应和多维正常声光效应的研究，选定了四方晶系的KDP晶体和立方晶系的GaP晶体作为多维正常声电光器件的最佳晶体，并通过计算两种晶体的声光互作用性能参量，确定了它们的二维、三维、四维正常声电光效应的最佳工作模式。研究结果为多维正常声电光器件的设计与制作打下了良好基础。多维声电光器件在多路光通信和多通道光信息处理中有应用前景。     

多通道声光调制器的工作原理

本文研究由多个电极产生的互相独立的多束并行超声波信号同时与一束光波的相互作用，建立了相应的耦合波方程并求出其解，分析了多通道超声波之间的交叉串扰及其对衍射光的影响，计算了相邻电极之间的最佳距离。以最佳距离作为设计参数，研制了多通道光调制器件，实验结果表明这样的声光器件可以完成多路并行调制。     

二维声光互作用理论及实验分析

本文在理论上推导了二维声光互作用的耦合波方程的普适形式,并借以对正常声光互作用下的喇曼-奈斯(Raman-Nath)型衍射进行了求解,所得结果与两个一维喇曼-奈斯型声光调制器组成的两维器件的实验结果进行比较,两者相符.     

金属纳米颗粒与二维材料异质结构的界面调控和物理性质

二维材料具有原子级光滑表面、纳米级厚度和超高的比表面积,是研究金属纳米颗粒与二维材料的界面相互作用,实时、原位观察金属纳米颗粒的表面原子迁移、结构演化和聚合等热力学行为的重要载体.设计和构筑金属纳米颗粒与二维材料异质结构界面,在原子尺度分析和表征界面结构,揭示材料结构和性能之间的相互关系,对于理解其相互作用和优化器件性能具有重要价值.本文总结了近年来金属纳米颗粒在二维材料表面成核、生长、结构演化及其表征的最新进展,分析了金属纳米颗粒对二维材料晶体结构、电子态、能带结构的影响,探讨了可能的界面应变、界面反应,及其对电学和光学等性质的调控,讨论了金属纳米颗粒对基于二维材料的场效应管器件和光电器件的性能提升策略.为从原子、电子层次揭示微结构、界面原子构型等影响金属纳米颗粒-二维材料异质结性能的物理机制,为金属-二维材料异质结构的研制及其在电子器件、光电器件、能源器件等领域的应用奠定了基础.     

超声跟踪反常氯化亚汞声光器件的设计及性能分析

氯化亚汞（Ｈｇ２Ｃｌ２）单晶具有独特的声光特性，这使得Ｈｇ２Ｃｌ２声光器件－Ｂｒａｇｇ盒适用于各种光信号处理。本文以超声跟踪反常器件的设计思想为基础，得出了Ｈｇ２Ｃｌ２器件的设计参数，并分析了这类新型器件的性能。结果表明，该器件有良好的性能，特别是其体积比同类ＴｅＯ２器件小得多。这些优点使之可望成为二维声光信号处理系统的关键器件。     

声光信号处理和光计算

由于激光的出现和发展及高性能超声延迟线的实现。产生了激光技术与超声技术相结合的新型声光信号处理技术。声光器件具有带宽大、实时性高和并行处理能力强等优点。在光信号处理、光计算、光通信、激光技术(如光调制、偏转、调Q、锁模、腔倒空等)和其它领域中有广泛的应用。本文将简要介绍声光效应在光信号处理和光计算中的应用。光信号处理和光计算没有一个明显的界限。早期人们习惯认为光信号处理只是光学图象的处理。而光计算则限于数值计算。现在二者的概念都大大扩展了。新一代计算机要求的人工智能功能例如图象的识别、推理、分析、判断等已不只是数值计算问题。光计算和光信号处理是密切相关的。 声光器件是通过光波和超声波在介质中相互作用。来控制激光辐射。声光相互作用可分为体光波与体声波的相互作用。导光波和声表面波的相互作用。体光波与声表面波的相互作用,由此制成相应的体波和表面波声光器件。我们仅以体光波和体声波及相应的体波器件为主进行讨论。 一 声光相互作用简述 声光学是研究光波和声波在介质中的相互作用。1922年布里渊首次预言到声光相互作用的存在。1932年由美国的德拜和希思,法国的卢卡斯和毕瓜德在实验上得到证明。在激光出现以前由于它引起光的变化     

声光器件及其应用

声光器件,即用声光效应制做的元器件。它通过在介质内传播的超声波和光波之间的相互作用,达到控制光束的目的。声光器件所产生的频移和偏转角都很小,所以对非相干光没有什么实用价值。由于激光束的单色性好,方向性好,亮度高,并且整个激光束能量可以全部聚焦在衍射限大小的光斑内,所以通过声光器件可以对它的频率,方向和强度进行快速而有效的控制。声光器件的种类繁多,应用面很广。本文重点论述声光偏转和声光调制器的基本结构、工作原理、基本的设计特点、工作方式等,并侧重介绍了对激光束控制方面的应用。     

晶体与电极位置失配对声光移频器性能的影响研究

为了提高声光移频器的性能,对其内部声光晶体(AOC)和压电超声换能器(PZT)电极之间的位置失配特性进行研究,并深入分析AOC和PZT电极之间几类不同的几何装配错位关系.通过构造AOC与电极失配的三维有限元模型,在不同轴向装配错位的条件下对AOC中的超声波声场进行仿真分析.根据超声波的声场分布特性,可以发现几何装配错位会导致AOC内部形成不发生声光相互作用的区域,并揭示此区域长度与错位量的关系.通过分析声光相互作用区与不发生声光相互作用区之间的光学界面,发现位置失配会在输出光中发生双光束干涉效应,其对实际光学系统的输出会产生影响.基于双光束干涉原理搭建一种测量不发生声光相互作用区域长度的实验系统,所得结果证明理论分析的合理性.     

集成光学声光可调谐光谱仪的特性分析

提出了一种以集成光学声光可调谐滤波器作为分光元件的新型光谱仪 ,并详细介绍了这种光谱仪的具体特性。通过对这种光谱仪的特征方程、点扩展函数以及色散本领的详细分析 ,指出该光谱仪的分辨本领与器件的声光作用长度成正比 ,也与它的级联级数的平方根成正比。因此增加器件的声光作用长度比增加它的级联级数能更有效地提高光谱分辨率。另外还指出 ,准共线声光耦合是抑制侧瓣、提高分辨本领的有效途径。测试表明 ,当声光相互作用长度L =2 5mm ,声波导和光波导的夹角θ=0 .4 2°时 ,在中心频率 174MHz附近可获得带宽 1.4 4nm ,一级侧瓣 - 13.2dB ,模式转换效率大于 99%的结果。     

声光器件的频率反馈双稳态

报道了利用声光器件和具有频率反馈功能的声光器件驱动电源所进行的频率反馈双稳态实验，并将实验结果与理论分析进行了比较，得出相符合的结果。     

Two-dimensional multi-channel acousto-optic diffraction

In this paper, we have investigated the interaction between acoustic waves generated by an incident light beam propagating through two-dimensional transducers. A set of coupled mode equations for two-dimensional multi-channel acousto-optic inter-modulation are derived, and the solutions are obtained. A new type of two-dimensional multi-channel Bragg acousto-optic modulator is designed by analyzing two-dimensional multi-channel acousto-optic inter-modulation based on the coupled mode theory, and its performance has also been experimentally characterized. The experimental results are in accordance with our theoretical analysis.     

Multichannel vector sum phase shifter

A novel multichannel vector sum phase shifter that is suitable for phased array antenna applications is demonstrated. Each channel is implemented using a distinct optical wavelength. Selective control of each channel is performed using an acousto-optic polarization coupler. The concept is successfully demonstrated for two individually controlled channels. For each channel, a continuously variable frequency linear phase shift is demonstrated between DC and 7 GHz, with the phasing range exceeding 100 degrees.     

Multifrequency acousto-optic page composers for holographic data storage

A new concept for one- and two-dimensional acousto-optic page composers to be used in holographic memories is proposed and experimentally demonstrated. The concept is based on multifrequency operation and compensation of the Doppler shift of the optical frequencies. Acousto-optic page composers without the usual exposure time limitation are in this way realized.     

Analysis of the Chirped Super Moiré Gratings Based on Acousto-Optical Superlattices

There are multiple passbands in a chirped Bragg grating based on acousto-optic superlattice. The structure can be regarded as an acousto-induced super Moiré grating (AI-SMG). The analysis shows that the passbands of the AI-SMG are produced by several pairs of neighboring chirped gratings. With suitable structure parameters selected, the passbands can be non-larenzian-shape, narrow flat-top, with ripple less than 0.5dB and steep slope. The devices can be used as tunable narrow-band multichannel transmission filters. This analysis is useful for the designs and applications of the devices.     

Acousto-optical diagnostics of Gulyaev-Bleustein waves under Fresnel reflection conditions

Diffraction of light by ultrasonic Gulyaev-Bleustein waves is studied under Fresnel reflection conditions. It is shown that Gulyaev-Bleustein waves propagating in GaAs-AlGaAs structures can be detected by acousto-optic methods under conditions for Fresnel reflection of diffracted waves. It has been established that the considered structures are promising for design of multichannel acousto-optical deflectors and modulators. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 75, No. 4, pp. 583–587, July–August, 2008.     

Acousto-optic diffraction with allowance for the influence of the acousto-optic cell boundaries

The influence of the dimension of an acousto-optic cell in the plane orthogonal to the plane of acousto-optic diffraction on the acoustic field structure and, consequently, on acousto-optic diffraction is studied theoretically and experimentally. A method is suggested for approximate calculation of the acoustic field with regard to the acoustic column reflection from the crystal faces. Based on this method, the influence of the acousto-optic cell dimensions is analyzed in a wide range of ratios between the height of the piezoelectric transducer and the height of the crystal. A region of acoustic power concentration is predicted to arise both for parallel faces and for slight wedging. A number of statements are demonstrated with paratellurite used as an interaction medium. The results may be useful in designing acousto-optic devices.     

High-transmission two-crystal acousto-optic monochromator

A two-crystal high-transmission acousto-optic monochromator is developed and studied. The transmittance of the monochromator can substantially be increased and the scheme can be simplified using the reflection from a face of the acousto-optic cell as a separating polarizer. The intervals of parameters of acousto-optic interaction (angles and wavelengths) that correspond to high efficiency of the monochromator are found. Characteristics of two high-transmission monochromators with different parameters of the acousto-optic interaction are determined.     

A phenomenological Landauer-type theory on colossal magnetoresistance

A two-dimensional interacting magnetic domains model is examined to explain the colossal magnetoresistance (CMR) recently observed in manganese-oxides. Electrons transport properties were studied by using Landauer's multichannel transport theory and recursive Green's function technique. Colossal magnetoresistance shows up in this system. The temperature dependence of system's MR is also studied.     

Compact interrogator for fiber optic Bragg sensors based on an acousto-optic filter formed by photonic crystal rows of air holes

Fiber optic sensors are typically used with expensive tunable lasers or optical spectrum analyzers for wavelength interrogation. We propose to replace the tunable laser by a broadband optical source incorporated with a novel thin linewidth acousto-optic tunable filter. It utilizes optical beam expanders constituted by photonic crystal rows of air holes in LiNbO(3) waveguide. A new design is numerically studied for a short structure (with 32 photonic crystal rows) by a two-dimensional finite-difference time-domain method. Extrapolation of these results to larger structure sizes (about 1 cm) demonstrates the possibility to develop compact interrogators with 0.4 pm wavelength resolution and 40 nm tunable range around 1550 nm.     

Compact acousto-optic filter with beam expanders constituted by photonic crystal rows of airholes

A compact acousto-optic (AO) filter with multireflector (MR) beam expanders constituted by 32 photonic crystal rows of airholes in LiNbO(3) waveguide has been proposed and numerically studied by the two-dimensional finite-difference-time-domain method. The diameter and position of every row of holes are gradually varied along MR beam expanders in order to provide high efficiency and good sidelobe suppression. Device sizes are 70 μm × 150 μm, with an FWHM bandwidth of 4.4 nm, a tuning range of 110 nm, internal loss of -3 dB, and sidelobes of -20 dB, thus providing a unique value of 0.6 μm(2) for the product FWHM bandwidth by an AO length. It is intended for use in fiber optics telecommunications and sensing.