光栅实验衍射的成象问题

讨论了光学实验中光栅衍射成象的问题。     

光栅与全息照相

基于普物光学的双光束干涉和光栅衍射，定性分析全息照相。     

水下微光高速光电成象系统作用距离的研究

本文首先对水的光学特性及其对水下成象的影响进行了分析,指出了水下光学成象的特殊性对光电成象器件的要求,并对微光条件下光电成象器件的性能进行了理论分析;详细介绍了水下微光高速光电成象系统作用距离公式的推导过程;最后针对实际系统进行了计算和分析.     

光纤光栅多传感器复用的成象光谱技术

本文根据光纤光栅多传感器复用时信号的光谱特征,提出了采用成象光谱技术对复用信号进行解调的方案.文章推导分析了该复用方案的有关参量及特性,并进行了验证实验,获得了与计算结果吻合的实验结果.     

用错位相位光栅产生的可调光学双阱

提出了用相位型错位光栅产生光学双阱的新方案.用平面光波(或TEM₀₀模式高斯光波)照射、正透镜聚焦,在透镜焦平面上产生的适用于冷原子或冷分子囚禁的多对可调光学双阱.计算和推导了双阱的光强分布、强度梯度以及光阱的几何参数与光学系统参数间的解析关系,研究了双阱到单阱三种不同的演化过程.同时还计算了光学双阱囚禁冷原子的光学偶极势和光子散射速率.研究发现,该方案不仅简单可行、操作方便,而且在原子物理、原子光学、分子光学和量子光学领域中有着广阔的应用前景. 关键词： 原子光学 相位光栅 光学双阱 冷原子囚禁     

一种新型的光栅成象型位移传感器

光栅的成象效应是光栅被点光源或扩展光源照明后自成象的一种特殊效应。该文应用傅里叶光学原理对扩展光源照明下光栅的成象特性作了分析,并由此设计出一种新型的光栅成象型位移传感器。     

双光栅快速扫描光学延迟线的色散补偿

光学相干层析成像(OCT)系统的纵向分辨力不仅与光源的带宽有关,而且与系统中两干涉臂间的色散匹配有关。如果色散没有得到精确匹配,将使光学相干层析成像系统的纵向分辨力达不到所预期的理论值。色散问题在超高分辨光学相干层析成像系统中尤为突出。提出了一种基于双光栅快速扫描光学延迟线(RSOD),用于光学相干层析成像系统的色散补偿。该方法中新增的光栅引入了光栅间距这一独立变量,其与常规单光栅快速扫描光学延迟线机构中的光栅离焦量一起,可使光学相干层析成像系统中的群速度色散(GVD)和三阶色散(TOD)同时得到补偿。分析了双光栅快速扫描光学延迟线的色散特性和色散调节原则,并提供了一个典型光学相干层析成像系统中的色散补偿实例。     

光栅光学双稳态

本文报道了一种光栅光学双稳态装置.利用改变一对对称光栅间相对位移,实现了对透过光强的周期性调制.将这样的系统作为传输部分,分别用He-Ne激光和普通白光完成了光学双稳实验.实验结果与理论分析相符.     

利用平面平晶反射干涉制作低频全息光栅

基于对光栅制作方法优缺点的分析,提出了利用平面平晶双光束干涉原理制作低频全息光栅的方案.在保证光栅质量的前提下,简化了原有全息光栅制作的光路,实验证明简化后的光路是可行的,所制得的全息光栅可用于光学教学实验.     

全息液晶/聚合物透射光栅光学各向异性的研究

基于聚合物支撑(polymer scaffolding)形貌的全息液晶/聚合物透射光栅, 系统研究了光栅的光学各向异性. 在这种形貌的光栅内, 液晶不是以液滴的形态存在于富液晶区, 据此建立了相应光栅的简化模型, 然后在各向异性耦合波理论框架下研究了光栅的衍射特性. 详尽的衍射效率实验值和计算值比较, 很好解释了液晶/聚合物光栅的光学各向异性, 也证实了液晶分子大致沿着光栅矢量排列.     

体全息成像系统中非周期体光栅的深度选择性研究

由一束球面波和一束平面波或者两束球面波干涉所形成的体全息光栅,由于其光栅矢量在全息图体积内是随位置的变化而变化的,所以被称为非周期型的体光栅。主要研究了用于体全息三维成像系统的非周期体光栅的深度选择特性。根据叠加的原理,将非周期体光栅看作多个固定周期的基元体光栅的叠加,结合耦合波理论分析非周期体光栅的衍射特性。采用这一方法,利用Matlab软件模拟,研究了两束记录光夹角对所记录的非周期体光栅深度选择性的影响和在两束记录光夹角相同时,球面参考光体全息成像系统及平面参考光体全息成像系统深度选择性的差别,最后在光折变晶体材料中进行非周期型和周期型体光栅的记录和再现,对模拟结果进行了实验验证。     

Identifying a dot-matrix hologram by checking the intersecting angles of its gratings

Three features about the intersecting state of two gratings are used to identify dot-matrix holograms created by two-beam writers in this paper. The first feature is the intersection angle of the fringes of two gratings. The second feature is the ratio of the pitches of two lowest-order moiré-patterns formed by overlapping two gratings. The third feature is the length ratio of the two diagonal lines of a parallelogram constructed by two neighboring fringes of a first grating and two neighboring fringes of a second grating. All the three features are equivalent, i.e. they are all relative to the intersection angle of two gratings. Because the grating orientations of grating dots cannot be accurately reproduced for the orientation uncertainties of the components used by a two-beam writer, the intersection angles of the gratings of grating dots cannot be easily counterfeited. Therefore, the proposed methods are practical and feasible for the anti-counterfeiting applications of dot-matrix holograms.     

基于双光栅成像的RGB模型色彩还原效果的研究

基于双光栅衍射成像的实验方案,利用双光栅的色散和汇合光谱效应特性,用电脑摄像头拍摄作为物体的RGB模型,得到了RGB颜色模型的像。利用Photo shop软件将RGB颜色模型和得到的像进行颜色通道分离,再进行数据化分析处理,探究双光栅的RGB色彩模型色彩还原情况以及不同光栅组合对RGB颜色模型的色彩还原效果的影响。     

用菲涅耳衍射理论分析双光栅成像效应

从理论上对双光栅成像效应现象进行研究,分别从菲涅耳衍射理论和平面透射光栅的菲涅耳衍射公式出发,分析了物光波经过两个平行放置的平面透射光栅组成的系统衍射后的复振幅分布。分析结果表明,在理想状态下,当两个光栅的放置位置满足一定条件时,在第二个光栅后面可以观察到一个清晰的原物体图像。理论分析解释了两个光栅在双光栅成像效应中的作用,得到了双光栅成像效应发生时,两个光栅的空间频率、衍射光级数以及光栅放置位置之间的关系式,这与实验所得结果相一致。     

Anomalous behaviour of long-time increase in diffraction efficiency of photorefractive grating in Ce：BaTiO3 in dark

Anomalous long-time increase of the diffraction efficiency is observed in dark-decay experiments of photorefractive gratings in Ce：BaTiO3. It is deduced that a phase-conjugate beam is induced by the writing beam at acute angle to the ＋c axis of the crystal and it interferes with the other writing beam to form a second grating which is perpendicular to the first grating formed by the interference between two writing beams. The rising behaviour of the diffraction efficiency results from the different decay rates of these two photorefractive gratings. Furthermore, a simplified model of two gratings, both induced by two deep traps, is proposed to account for this phenomenon and the fitting results agree well with the experimental results.     

非线性二次曝光法制作三角形光纤Bragg光栅

提出了一种利用非线性二次曝光技术制作三角形光纤Bragg光栅的新方法.该方法只使用普通Bragg位相模板,采用两次曝光技术,通过控制光纤光栅的本地谐振波长和反射率,达到控制光纤光栅谱形的目的.第一次直接对光纤曝光,用来控制光纤光栅谐振波长;第二次通过位相模板曝光,用来控制光纤光栅的反射率.考虑到光敏光纤感光特性曲线的多项e负指数变化规律,按照"分步写入光纤光栅设计软件"进行曝光分布设计,利用"分步曝光光纤光栅写入系统"进行曝光控制,使用信息产业部第46研究所生产的DCS-01型光敏光纤,得到了线性范围1.24 nm、反射率为0～64%的三角形光纤Bragg光栅.三角形光纤Bragg光栅作为光纤光栅传感解调器件,在光纤传感领域具有重要应用价值.     

Nonlinear optical properties of composites based on conductive metal-alkanoate liquid crystals

The dynamic holography in new composite materials based on a novel class of metal-alkanoate ionic liquid crystals (ILCs) is studied experimentally and theoretically. The composites are formed as a dielectric dye film covered by lyotropic metal-alkanoate ILC and ionic smectic glasses with doped dye molecules. The dynamic gratings are created by nanosecond pulses of double frequency Nd:YAP laser, the recording demonstrates fast erasure time of residual thermal gratings. The nonlinear optical properties are determined by the resonance nonlinearity in photosensitive centres of ILC. Note, that permanent relief gratings will be formed on a dielectric dye film only as well as in composite cells either with nematic LC or with polymers under action of pulsed laser radiation. Lyotropic ILC layer applied over the dye film provides the dynamic regime of grating recording in composite cells. We found a secondary thermal grating is much smaller, the conductive ILC matrix provides effective heat dissipation and erasure of this thermal grating. A theory of Raman-Nath self-diffraction holography on thin films followed from the wave equation and the nonlinear mechanism of absorption saturation is developed to explain experimental results.     

The spectral combination characteristic of grating and the bi-grating diffraction imaging effect

This paper reports on a new property of grating, namely spectral combination, and on bi-grating diffraction imaging that is based on spectral combination. The spectral combination characteristic of a grating is the capability of combining multiple light beams of different wavelengths incident from specific angles into a single beam. The bi-grating diffraction imaging is the formation of the image of an object with two gratings: the first grating disperses the multi-color light beams from the object and the second combines the dispersed light beams to form the image. We gave the conditions necessary for obtaining the spectral combination. We also presented the equations that relate the two gratings’ spatial frequencies, diffraction orders and positions necessary for obtaining the bi-grating diffraction imaging.     

Thin and thick diffraction gratings: Thin matrix decomposition method

A brief review of the properties of transmission diffraction gratings is presented. Two types of gratings will be analyzed: thin and volume gratings explaining how the efficiency of the different orders that propagate inside the gratings can be calculated in both cases. For thin diffraction gratings the so-called amplitude transmittance method is applied in order to get the amplitude of the different orders, whereas in the case of volume gratings more complex methods are needed, such as Coupled Wave or modal theories. We will comment on the thin matrix decomposition method (TMDM), firstly proposed by Alferness, which gives a very intuitive approach and connects the properties of thin gratings to the properties of volume ones. The thin matrix decomposition method consists in dividing the volume grating in a number of thin gratings and applying the amplitude transmittance method to each thin grating. In this way the output of a grating will be considered as the input of the next and any individual grating can be treated by the amplitude transmittance method. The novelty of this work is that a comparison is made between the analytical expressions obtained by Alferness using the TMDM with the numerical results obtained using the coupled wave (CW) and rigorous coupled wave (RCW) theories for the efficiencies of the zero, first and second order when a plane wave incides onto a sinusoidal diffracion grating at the second on-Bragg replay angular condition.     

BR-PVA固体膜在四波混频相干场中的光栅特性和位相共轭波的暂态行为

利用Ar离子激光简并四波混频(DFWM)技术,对细菌视紫质(BR)-聚乙烯醇(PVA)固体膜的位相共轭波特性进行了理论和实验研究。采用BR光循环的双态模型和粒子数速率方程,以及全息光栅理论描述了该体系的PC波的衍射效率、时间响应和饱和特性,给出了相应的表达式。讨论了该体系在DFWM场中的光栅机制和上述特性对于输入波的偏振态,强度和强度比,到达样品的时间和形成的初始浓度光栅等参数的依赖关系。实验结果与理论分析相符。