用简并的四波混频测量介质的三阶极化率

本文研究了各种透明介质的简并的四波混频作用。通过测量后向反射波与入射波的强度比,可以确定介质的三阶极化率。并给出了各种液体介质和玻璃的测量结果。 关键词：     

基于MATLAB软件对不同偏振光在不同介质中的传播过程的动态模拟

利用MATLAB软件对不同偏振光在真空、各向同性介质、线型各向异性介质以及圆型各向异性介质中的传播过程进行了三维动态模拟,能够加深学生对光的偏振概念以及各种偏振光与不同介质之间相互作用原理的理解。     

二维欧拉多介质流体力学数值模拟-TVD＋VOF方法

用TVD格式结合VOF界面处理方法编制了二维多介质高分辨欧拉程序，以解决冲击波和多介质界面处理。程序包括单介质网格高精度流体力学计算、多介质网格内界面重构、各种介质输运和压力驰豫平衡过程。其中单介质网格的计算采用Harten二阶TVD格式结合MacCormark方法计算含有源项的非齐次守恒定律方程组，通过4节点限制函数保证格式单调。多介质网格采用Youngs方法构造界面，采用x，y方向分裂格式计算体积份额输运，再根据体积份额输运计算质量、动量和能量的输运，最后利用等熵条件计算各种介质的压力驰豫平衡过程。     

光波弱散射过程中的统计光学特性

光波经介质散射后的远场光学特性,包括光谱强度、光谱相干度以及光谱偏振度等,与散射介质的结构特征密切相关。近年来,光波弱散射现象的研究取得了较大进展,一方面,研究人员将散射体推广到各种介质,包括各向异性介质、半软边介质、椭球形介质等;另一方面,研究人员将入射光波推广到各种常见的光束,如随机电磁光波、平面波脉冲光束、非匀幅光束等。介绍了关于光波弱散射问题的主要研究成果,包括光波散射过程中的光谱变化现象、相干性变化现象、等价理论、互易关系以及光波散射逆问题等。     

固体介质中的电磁感应透明效应及其应用

电磁感应透明技术不仅能够改变物质对光场的响应，而且能够调控光场本身的性质．文章介绍了电磁感应透明效应的基本原理，电磁感应透明现象在各种固体介质中的实现，比较了这些固体介质的特性，并讨论了由电磁感应透明现象所产生的各种效应及其应用．     

国外光学与光电子学的新进展(Ⅶ)——可调谐激光器:固体化发展趋势

<正> 80年代,可调谐激光器增益介质的发展趋向于从液体转向固体材料。染料激光器作为实用化的可调谐激光光源在70年代得到了广泛的应用,然而它的霸主地位却由于80年代末期几种固体可用调谐激光器的出现而受到削弱。本文概述导致目前各种实用化可调谐系统并存状况的各种研究发展工作所涉及的增益介质有染料、顺磁离子以及色心介质。     

微多孔介质非牛顿流体格子Boltzmann模拟

根据修正Blake-Kozeny方程对Herschel-Bulkley模型的非牛顿流体在微多孔介质中流动的定量描述,通过增加外力项建立了非牛顿流体在宏观多孔介质中的格子Boltzmann模型,并将该模型应用到平板多孔介质中非牛顿流体的电渗驱动流模拟。对多孔介质渗透性参数和非牛顿流体流变性参数的影响进行模拟和分析,获得了各种参数对多孔介质中非牛顿流体流动速度的影响规律。     

径向梯度介质中远轴细光束保径传播的理论证明

本文从理论上证明,由于各种表面效应和光在焦点处的特殊性质及径向梯度介质的本征非线性作用,凡经聚焦而进入径向梯度介质的细光束,均会产生稳态半自陷而保径传播。这为开辟该介质的应用提供了新的理论根据。     

薄透镜在不同介质中的会聚与发散性质

从薄透镜的焦距公式出发,讨论了各种透镜在不同介质中的会聚与发散性质.透镜的会聚、发散性质既与透镜的形状和折射率有关,又与透镜两侧介质的折射率有关.     

液芯光纤中的非线性效应

液芯光纤作为非线性介质不仅具有光纤本身所特有的各种特性,而且还具有液芯介质所决定的各种特性,在非线性光学效应的研究中具有理论和实用意义。我们已观察到几种在普通石英光纤中不曾观察到的非线性效应。本文着重报导在液芯光纤长增益条件下受激喇曼散射及其级联过程的实验结果。     

记录方式对光致聚合物中全息光栅形成过程的影响

根据光致聚合物记录机理,研究了不同记录方式对光栅衍射效率的影响.对已有的光致聚合物光栅形成的一阶扩散模型进行简化,求解出全息曝光、暗增长、均匀后曝光过程对应的折射率调制度的解析式.应用所得解析结果,对三种记录方式在不同光强下的折射率调制度动态进行数值模拟.采用蓝敏光致聚合物,分别在4 mW/cm~2和2 mW/cm~2光强下应用不同方式记录光栅,结果表明:如果曝光光强较高,暗增长的记录方式将获得相对高的饱和折射率调制度,而均匀后曝光会加速达到饱和的进程.     

Characteristics of reverse overwrite process in shingled recording scheme at ultra-high track density

A systematic experimental study of the reverse overwrite (ReOVW) process in the shingled recording scheme has been conducted in conjunction with characterization of corresponding recording performances from recording heads with different geometries. It was found that there is no ReOVW reduction as the track density increases in a strict shingled recording fashion. Nonetheless, ReOVW is indeed slightly decreased from 300 to 700 kpi in a so-called one write shingled recording process. Overall our obtained data suggest that conventional magnetic recording technology might be able to extend all the way beyond an areal density of one Tbit/in² by using the shingled recording scheme.     

Grating spacing dependence of nonvolatile holographic recording with arbitrary charge transport lengths

Grating spacing dependence of nonvolatile holographic recording in doubly doped lithium niobate crystals is theoretically investigated allowing arbitrary charge transport lengths. It is shown that the nonvolatile refractive index modulation initially increases with increasing grating spacing, then a saturation behavior arises because of the dominant bulk photovoltaic effect. Although different charge transport length results in different nonvolatile refractive index modulation, the grating spacing dependence of nonvolatile holographic recording obeys almost the same rules for arbitrary charge transport lengths. The experimental results obtained by recording nonvolatile holograms in LiNbO₃:Cu:Ce crystals with different grating spacing are consistent with the theoretical analyses.     

LD相对于铯原子超精细跃迁线的偏频锁定

Holographic storage properties of iron-doped and cerium/iron-doped LiNbO3 with different doping concentrations and treatment conditions have been measured for different recording wavelengths. The results show that at recording wavelengths of 532 nm and 633 nm the holographic storage properties of Ce:Fe:LiNbO3 are generally better than those of Fe:LiNbO3.     

The Comparison of the Holographic Storage Properties of Fe:LiNbO3 and Fe:Ce:LiNbO3 Crystals

Holographic storage properties of iron-doped and cerium/iron-doped LiNbO3 with different doping concentrations and treatment conditions have been measured for different recording wavelengths. The results show that at recording wavelengths of 532 nm and 633 nm the holographic storage properties of Ce:Fe:LiNbO3 are generally better than those of Fe:LiNbO3.     

Read and write processes, and head technology for perpendicular recording

In this paper, we present a review of the write and read processes in perpendicular magnetic recording. We also discuss their impact, based on recording physics aspects, on design considerations for writers and readers. For the write process, we discuss fundamental write-ability limitations as well as possible paths to ultra-high areal density perpendicular recording. The impacts of different medium designs, geometrical scaling, and the breakdown of scaling, both in terms of write-ability and transition curvature, are shown based on different modeling techniques, including analytical formulas, finite element modeling (FEM), and micromagnetic simulations. Basic design rules as well as alternative designs that enable high areal density are briefly explained. For the read-back process, the relation between reader signal to noise ratio (SNR) and resistance, as well as reader resistance shunt and spacing loss, are discussed. Finally, we use a simple example to illustrate, both from a write as well as a read-back perspective, the complicated nature of perpendicular recording systems, and how different medium designs impact recording head technology for ultra high density perpendicular recording.     

A comprehensive picture of magnetic recording: theory and experiment part I: fundamentals and digital recording

The present paper summarizes and extends previous publications on magnetic recording which described a recording model, that offers the possibility of quantifying the importance of various parameters of the medium and the hardware. Within this model computer simulations of the read/write process elucidate the broad scope of magnetic recording to an extent, nonexistent so far. All computations follow or adapt common measuring procedures which facilitate the verification of our theoretical findings by comparison with experimental data. In this first of two papers the theoretical analysis applies to digital recording, only. The presented results permit objective comparisons between different techniques and media. Moreover, they yield clear statements about the feasibility for improvements of magnetic recording.     

Effect and optimization of the diminution of the sensitizing intensity in two-center recording

The effect of the diminution of the sensitizing intensity from initially high value on two-center recording is experimentally and theoretically investigated. A linear diminution of the sensitizing intensity is designed,and three different diminution rates are employed for the experimental investigation. The results show that the dynamic range can be improved by reducing the diminution rate of the sensitizing intensity. Compared with that of traditional two-center recording, the recording sensitivity obtained in the experiment is more improved when the maximum dynamic range is achieved. The effect of the diminution of the sensitizing intensity on grating uniformity and the effect of the initial sensitizing intensity on the recording sensitivity are theoretically investigated.     

多阶光存储原理分析及其读写系统前端信号处理研究

运用矢量衍射理论的计算方法(耦合波方法，时域有限差分法)，对两种多阶光存储方案(坑深调制，坑形调制)进行了原理性分析，并简略分析了利用相变材料的幅值调制实现多阶存储的原理.由此得出多阶光存储技术的实现是利用了光与物质之间的相互作用，使光对记录介质产生作用，同时介质也对光的某些特性进行调制，而这些特征的改变一般都不止两个状态0或1，用数字方式将这多个状态记录下来便实现了多阶数字存储.此外,还提出了多阶光盘前端信号处理系统的设计与开发.该系统是多阶光存储实验系统的重要组成部分，可输出RF,TE,FE等伺服与误差信号，并将信号反馈给多阶处理芯片；同时系统还可对光学头的激光读写功率及写入时间进行控制，并能使其实现自动调焦和道跟踪. 关键词： 多阶光存储 矢量衍射理论 时域有限差分法     

数字重现无透镜傅里叶变换X射线全息的实验模拟研究

参照无透镜傅里叶变换（ＬＬＦＴ）Ｘ射线全息图的记录光路，采用可见光源模拟研究了无透镜傅里叶变换Ｘ射线全息从记录到数字重现的全过程，给出了实验结果，并对光学重现和数字重现结果作了比较，分析了该记录方式存在的一些问题，指出实际Ｘ射线全息记录中可直接使用波带板＋１级衍射而不必在物面加一滤波小孔。分析了利用数字重现消除记录过程中非线性效应的可行性。并着重指出波带板的多级衍射的互干涉对重现象的干扰，应设法消除。