光纤干涉成像阵列全息相位校正研究

针对光纤传输和干涉成像阵列中的相位误差, 提出了一种基于特殊光子晶体的全息相位校正方法。首先分析了光纤干涉阵列成像的基本原理和相位信息的传输过程, 以一维线性阵列建立成像系统相位误差模型, 通过对参考光束和探测器前的快门交替打开和闭合, 来分别实现在晶体上写入由光纤阵列的出射光束与参考光束干涉形成的含有相位误差的光栅函数, 和光纤中出射光束被该光栅衍射和相位偏移以消除相位误差, 从理论上分析了上述基于光子晶体的全息法相位校正原理。最后采用所建立的含有相位误差的干涉阵列进行成像仿真, 对未加校正、采用本文方法和采用冗余基线校正的结果进行了对比分析。     

1000幅数字图像的晶体体全息存储与恢复

利用Ｆｅ：ＬｉＮｂＯ３光折变晶体和角度多重方法，在晶体人的一个公共体积内实现了１０００多幅数字图像的存储与重建。由于同时采用差分编码与纠错编码，因而系统抗噪能力细，误码率低。整个同计算机控制，自动化程度高。     

Content-addressable Holographic Digital Data Storage Based on Hybrid Ternary Modulation with a Twisted-Nematic Liquid-Crystal Spatial Light Modulator

We propose and demonstrate the use of hybrid ternary modulated digital pages for content-addressable holographic data storage. Display of binary data pages with equal number of ZEROs and ONEs by modulating both amplitude and phase of beams using twisted-nematic liquid crystal spatial light modulator, reduces strong de component and produces a more homogeneous spectral distribution at the recording plane. This technique facilitates better recording of all spatial frequencies, thus improving the discrimination capability of a content-addressable memory. Hence we get better results in associative recall in a holographic memory system, with very low number of false hits. An important advantage of the hybrid ternary modulation over pure phase data pages is that it offers a dark state for coding the undesired portion of the SLM while the search argument is small. The unique orientation of quarter wave plate and the analyzer blocks the light transmitted from OFF pixels leading to near total removal of dark signals. This in turn improves the system performance and reduces the number of false hits when the size of the search argument is small. Our experimental results show good discrimination capability and signal-to-noise ratio for a hybrid ternary modulation based content addressable memory.     

莫尔条纹分析在数字全息存储器中的应用

针对像素不匹配的数字全息存储器中出现的莫尔条纹现象,提出了利用莫尔条纹进行全息存储光路精确调整来实现像素匹配的方法.通过对CCD像面图像中莫尔条纹的周期和角度进行分析,得到光学系统需要的精确调整参数.实验中, 实现了空间光调制器和光电耦合器阵列512×512像素的1∶1像素匹配,该方法能提高读取速度并降低误码率.     

莫尔条纹分析在数字全息存储器中的应用

针对像素不匹配的数字全息存储器中出现的莫尔条纹现象,提出了利用莫尔条纹进行全息存储光路精确调整来实现像素匹配的方法.通过对CCD像面图像中莫尔条纹的周期和角度进行分析,得到光学系统需要的精确调整参数.实验中,实现了空间光调制器和光电耦合器阵列512×512像素的1:1像素匹配,该方法能提高读取速度并降低误码率.     

绿敏光致聚合物的制备及其光全息存储性能研究

报导了一种新型的对绿光敏感的光致聚合物材料。该材料以丙烯酰胺为单体，由光引发剂，共引发剂，成膜物等组成。本材料记录的全息图衍射效率可达55％。在光聚物上采用角度复用技术存储了10幅图像，得到的再现像信噪比较高。说明该材料适合于大容量体全息存储。     

全息光盘存储器的数据存取与像素匹配

全息光盘存储(HDS)技术作为一种非常具有潜力的新型信息存储技术, 是下一代光盘发展的目标。在全息光盘存储系统中, 为了实现数据精确快速地写入和读出, 降低误码率, 需要在整个高分辨率页面上实现空间光调制器(SLM)与光电阵列耦合器(CCD)之间1∶1像素匹配。在体全息存储理论和光学设计理论基础上, 研究实现SLM和CCD像素1∶1匹配的方法, 提出了实现像素匹配的要求和条件, 并且按照此要求完成该全息光盘存储器的光学系统。实验中, 分别使用随机数据掩膜版和SLM实现了对CCD的512×512精确像素匹配, 在光学系统中引入存储介质条件下, 图像质量良好, 掩膜版和SLM原始误码率分别为2.5×10-4和1.5×10-4。     

体全息存储中二维交错编码技术的研究及实现

为了克服和纠正体全息存储系统中大量的随机错误和突发错误,数据在按"页面"为单位存入系统时,通常采用纠错编码、交错和调制相结合的编码方式来进行信息组页.文中提出了一种二维交错技术用于克服数据"页面"存在的突发错误,以提高纠错编码的纠错能力,并通过FPGA实现了块交错RS(255,223)编码码字在数据"页面"中的均匀分布.     

体全息子波关联记忆器

基于子波匹配相关理论和光折变晶体的体全息关联存储特性,提出并实现了一个关联记忆的新构思。中根据缺损特征实现原始图像的记忆和恢复,其中光折变晶体兼作图像识别时的运算单元和图像恢复时的存储单元,文中以人脸为研究对象,给出了实验结果。     

光致聚合物中单体及粘结剂对全息性能的影响

研究了单体及粘结剂等成份对全息光致聚合物薄膜光存储性能的影响。在相同引发条件下．以丙烯酰胺作为单体时，光聚物的衍射效率明显高于以丙烯酸和N羟甲基丙烯酰胺作为单体时光聚物的衍射效率。向丙烯酰胺中加入少量N-羟甲基丙烯酰胺，可以改善膜表面的光学质量．降低散射光强度，并提高膜的保存时间。在聚乙烯醇膜中单体聚合程度明显优于在聚乙烯吡咯烷酮中的程度，在大分子量的聚乙烯醇中的衍射效率及感光灵敏度高于在小分子量中的衍射效率和感光灵敏度，而且大分子量的聚乙烯醇能够制备厚膜，这是实现全息海量存储的一个重要因素。     

A Plane-Wave Beam-Steering Lens Design Using Microstrip Switched-Line Phase Shifters

A compact beam-steering lens design appropriate for millimeter-wave and submillimeter-wave applications is experimentally verified with an X-band test model. The lens achieves coupling to plane-wave beams through arrays of patch antennas placed on its two outer surfaces. The isolation between input and output antennas is accomplished by inserting a metal ground plane in the middle of the lens. The two closest patch antennas on the front and the backside are connected together with microstrip circuits that include switched-line phased shifters and interconnecting vias through the lens substrate. Three different X-band 100-element plane-wave microstrip lenses that use passive delay lines instead of actual phase-shifters were fabricated to successfully demonstrate the beam-steering angles of 20 and 40 degrees. From a separate waveguide measurement on the unit-cell element only, the insertion loss of the lens was estimated to be approximately 3.5 dB with bandwidth of 2% at 10 GHz.     

Improvement of Laser-Beam Irradiation-Intensity Distribution Using Multi Lens Array and Edge-Shaped Plates

A new concept for improving the laser intensity distribution on an inertial confinement fusion target using a phase-controlled multi lens array has been proposed. Circular and hexagonal element lens apertures have been examined, and the circular aperture which eliminated azimuthally asymmetric intensity distribution was chosen. The diffraction fringe of the elementary lens was mitigated in a one-dimensional lens array using edge-shaped plates of a super-Gaussian phase profile. Uniform beam profiles were obtained using a one-dimensional array with 7 spherical lenses and a two-dimensional array with 37 lenses. An approximately flat-top intensity distribution was realized with the lens array with 37 lenses.     

用微透镜阵列在单模光纤中写入长周期光纤光栅的新方法

报道了用微透镜阵列、几百个准分子激光脉冲有效地写入长周期光纤光栅的新方法。     

谱色散平滑与透镜列阵联用实现均匀照明

为满足激光惯性约束聚变中靶面激光辐照不均匀性低于5%的要求,在目前使用透镜列阵基础上,提出了谱色散平滑与透镜列阵联用方案,对其进行数值计算并分析其平滑效果和应用可行性。结果表明:焦斑的不均匀性从单独使用透镜列阵时的14%降低到与谱色散平滑结合后的3%;对焦斑点功率谱的分析表明谱色散平滑通过抑制焦斑中高频的频谱强度达到平滑效果。该方案可以进一步提高焦斑平滑效果,计算结果对实际应用有着重要的参考意义。     

基于数字全息干涉术的液相扩散过程可视化

提出了利用数字全息干涉术可视化观测液相扩散过程.实验中,采用马赫-曾德干涉仪光路记录乙醇与水之间两相扩散过程的多幅数字全息图;再通过数值再现不同扩散状态的波前相位分布,获得液体中的摩尔浓度分布;最后,根据菲克定律获得两相流扩散系数.结果表明:利用数字全息干涉术可实现对液相扩散传质过程的快速、实时及高精度测量;该方法还具有可实现远程监控、拥有大量微观数据的优点;此外,采用文中全息干涉光路结合波分与角分复用技术可实现多相流扩散系数的测量,为获得溶液中非线性变化特征参量提供了有效技术手段.     

可实现存储光栅快速增强的新型全息存储结构

提出一种新型全息数据存储结构，该结构包含两块存储的内容完全相同的光折变晶体，无需相位共轭器，仅利用两束时域快速调制的平面参光波便可实现对存储全息图的迅速增强。文章讨论了调制速率，读出光强比，晶体非线性耦合强度及初始光栅强度对增强速度及可获得的饱和衍射效率的影响。     

Beam Recombination Characteristics in Array Laser Amplification Using Stimulated Brillouin Scattering Phase Conjugation

Beam recombination characteristics were numerically investigated in array laser amplification using stimulated Brillouin scattering phase conjugation. To clarify the effect of piston errors due to imperfect phase locking, spatial intensity profiles of the beam recombination output were calculated in both the near and the far field on the basis of Rayleigh-Sommerfeld diffraction theory. The analyses indicate that piston errors are seriously detrimental to the quality of a beam recombination output and should be eliminated by a proper phase locking. It is also found that the gap between the beam splitting-combining wedges has a negligible effect.Presented at 1996 International Workshop on Interferometry (IWI ‘96), August 27-29, Saitama, Japan.     

Piano-Convex Solid Immersion Mirror with a Small Aperture for Near-field Optical Data Storage

We proposed and developed a new solid immersion mirror (SIM) for near-field optical data storage. The SIM has some advantages, especially in manufacturing, because its shape is similar to a general plano-convex lens. Making an aperture of about 130 nm in diameter just on the focus area of the SIM, a bit-data recording onto a photochromic thin film was carried out. Minimum diameter of the written marks was estimated to be 180nm. We also demonstrated readout experiments where a recorded medium was rotating and a gap between the SIM and the disk was controlled with capacitance sensing. This is the first result of reading with a rotating disk using an SIM containing a small aperture.This paper was originally presented at the 10th Optical Near Field Workshop, which was held on June 27-28, 2001 at Osaka University, organized by the Optical Near Field Group, the Optical Society of Japan, an affiliate of the Japan Society of Applied Physics.     

Investigation of Near-Field Imaging Characteristics of Radial Polarization for Application to Optical Data Storage

Radially polarized incident light can generate a more confined longitudinal electric field on a focal plane in near-field (NF) optics than focusing circularly polarized light. Using this phenomenon, it is feasible to reduce beam spot size on storage media to increase the areal density of optical data storage. A radially polarized beam generates a beam spot which is 20% more confined on the 1st surface of medium than that of circularly polarized light. However, the peak intensity of total electric field sharply decreases and its transverse component is much more dominant inside the media stack. This confirms that radially polarized optics can be a candidate not for an NF recording system but for an NF read-only memory (ROM) system. Potentially, the results could be useful to understand the effect of radial and circular polarizations inside and outside medium for various applications of NF optics.