High-resolution optical storage by use of minute spheres

We have developed a new optical storage system that uses minute spheres arranged upon a surface-relief grating. By using dye-doped minute spheres as recording bits we can limit a sensitive region within a sphere's diameter. Using a reflection-type confocal optical system, we read out shape signals from minute spheres at high resolution. The shape signals from minute spheres are utilized as clock signals in recording and readout.     

多层衍射元件的浮雕深度和基底材料的优化分析

在分析单层和多层衍射元件衍射效率的基础上,推导出光学系统中多层衍射元件浮雕深度和基底材料的一般关系式,并对这些变量进行优化,得到阿贝数的值大致在20～80之间,β的合理值在0.25～0.6之间,当2个衍射元件的阿贝数v1＜v2,且差值比较大时,阿贝数小的衍射元件的基底材料选择光学玻璃中的火石玻璃,阿贝数大的衍射元件的基底材料选择光学玻璃中的冕牌玻璃。根据这个方法,设计了3组可实现宽波段高衍射效率的不同材料、不同浮雕深度的组合,使得每组组合中两层衍射元件的衍射效率都在99%以上。     

Spatial Arrangement of Small Particles by Imaging Laser Trapping System

We describe spatial arrangement of polystyrene latex using a microscopic imaging system. A reduced photomask pattern is imaged on the particles in a water-filled cell so that polystyrene spheres align in a two-dimensional pattern. Calculating the forces exerted on the spheres by isolated line pattern, we investigated an optimum size for sphere diameter and the line width of the patterns. We are able to align spheres in real-time by this technique.     

基于白光干涉的光学球面半径测量研究

光学球面曲率半径是决定光学球面光学特性的重要参量,通过测量光学球面的曲率半径，可以审核光学元件设计制造质量。在基于白光干涉理论基础上，将莫尔光栅位移测量系统及CCD数字图像采集处理系统集成到迈克尔逊干涉仪上，利用CCD数字图像处理技术，构建了光学球面曲率半径自动测量系统。该测量系统对于大曲率半径的光学球面测量精度较高；对于半径R＝71.2037mm的光学球面,其测量标准误差σR＝0.4723mm。实验结果表明：设计的光学球面自动测量系统可以对大曲率半径光学球面实现高精度测量。     

Large area laser surface micro/nanopatterning by contact microsphere lens arrays

Laser surface micro/nanopatterning by particle lens arrays is a well-known technique. Enhanced optical fields can be achieved on a substrate when a laser beam passes through a self-assembled monolayer of silica microspheres placed on the substrate. This enhanced optical field is responsible for ablative material removal from the substrate resulting in a patterned surface. Because of the laser ablation, the microspheres are often ejected from the substrate during laser irradiation. This is a major issue impeding this technique to be used for large area texturing. We explored the possibility to retain the spheres on the substrate surface during laser irradiation. A picosecond laser system (wavelength of 515 nm, pulse duration 6.7 ps, repetition rate 400 kHz) was employed to write patterns through the lens array on a silicon substrate. In this experimental study, the pulse energy was found to be a key factor to realize surface patterning and retain the spheres during the process. When the laser pulse energy is set within the process window, the microspheres stay on the substrate during and after laser irradiation. Periodic patterns of nanoholes can be textured on the substrate surface. The spacing between the nanoholes is determined by the diameter of the microspheres. The depth of the nanoholes varies, depending on the number of laser pulses applied and pulse energy. Large area texturing can be made using overlapping pulses obtained through laser beam scanning.     

Study on the analogy feedback active soft edge noise barrier

It is feasible to enhance the effect of reduction of the noise barrier on low frequency noise using the active control system. On the basis of the forerunners’ research, an analogy feedback active control system that is easy to be carried out was arranged on the top of a noise barrier to form an analogy feedback active soft edge noise barrier in order to enhance the effect of reduction of the noise barrier on low frequency noise. Through a preliminary experimental study, this method was proved to be feasible and the following preliminary conclusions on the arrangement of active control systems were made: (1) when control sources were arranged in a single row, the control effect was determined by the density of arrangement: the higher the density, the better the control effect; (2) with the same density of arrangement, the control effect of the double row arrangement was better than that of the single row arrangement; (3) with the same number of control sources, the single row arrangement had better control effect than the double row arrangement.     

A Color Holographic Reconstruction System by Time Division Multiplexing with Reference Lights of Laser

3D-TV systems by holography technique have been studied in the world. In this paper, we report a color holographic reconstruction system by time division multiplexing method with reference lights of laser. The method can reconstruct a color holographic image by switching reference lights of red, green and blue colors at certain intervals. We can observe a color holographic image using red and green lasers as the reference lights, a high minute liquid crystal display (LCD) panel as a spatial light modulator (SLM) and electro-shutters as the shuttering device of the laser lights in the optical system. This approach has some advantages. Namely, the structure of the optical system can be simple and the number of LCD panels in the optical system can be decreased.     

Dependence of tracking error characteristics of in-line-type differential push-pull methods on arrangement error of segmented gratings

We present the validity of in-line-type differential push-pull methods using segmented gratings with respect to arrangement errors by numerical calculation for the first time. In these differential push-pull methods, the segmented gratings for generating subspots are divided into more than two regions, each with a specific width and a specific phase value, and are ideally arranged on the optical axis. We calculate tracking error signals in these methods with respect to the arrangement errors against the optical axis under parameter conditions of the widths of the segmented regions of the gratings. The obtained results show that the grating with a simpler configuration with two regions reveals good compatibility between DVD-recordable (DVD-R) and DVD-random access memory (DVD-RAM) compared with those with three or four regions, when the arrangement error is less than 10% of the radius of the incident laser beam.     

CONSTRUCTION OF AN OPTICAL TWEEZERS—CALCULATION AND EXPERIMENTS

We report the construction of an optical tweezers system and the results of the trapping and the moving of living algal cells. Experimental study on trapping polystyrene spheres demonstrates the effects of the system parameters on the trap. The trapping forces on dielectric spheres are calculated using Ashkin's ray-optics model. The result shows that an objective with higher numerical aperture can build a more stable trap along axial direction than an objective with lower numerical aperture, though their transverse trapping forces are on the same order.     

365 nm紫外LED二维空间阵列光学系统设计

针对紫外固化技术领域中新型大功率365 nm UV-LED光源进行了拓展性应用研究.提出了空间阵列排布实现能量累加的技术方案,给出了其优化设计原理与软件实例仿真结果.结果证明:该二维空间阵列光学设计方案的正确性和可行性,完全可以实现应用现场的实际光学技术指标（辐照度、光斑尺寸、后工作距离、光斑等）;其中指标要求在辐照面实现50 mm×10 mm线状辐照光斑,后工作距离≥50 mm,辐照度≥1 W/cm2,辐照面光斑分布均匀,设计出的空间阵列光学系统在结构上实现了最高优化设计.     

Finite-Difference-Time-Domain Analysis for Electro-Magnetic Field Distribution on Near-Field Optical Recording Probe Head

In recent years there has been a strong trend and movement towards digitalism and high memory capacity in the multi-media field including digital movies. It is expected that new kinds of high density data storage to match this environment will be developed. The optical disk system using near-field optics and technology is considered to be a strong candidate for ultra-high density optical memory. In order to realize a new optical recording system we have focused on the writing head with high optical efficiency and resolution. We evaluated the properties of pyramidal probe heads using the FDTD (finite difference time domain) method and obtained simulation results in order to find the best structure and design for new near-field optical probes. From these results, we understood that a novel probe structure having metal layers on just 3 side planes (scoop type) shows the best performance in optical power density and beam size. We believe that optical enhancement and beam confinement arise from the effect of surface plasmon on a metal layer and the beam blocking of metal, respectively. Using this scoop-type probe having a tip size of 55 nm, we can get a very small spot size of 33 #x00D7; 60 nm² in FWHM (full with half maximum), which allows us to realize the recording density of 300 Gb/in².     

Optical switching based on the manipulation of microparticles in a colloidal liquid using strong scattering force

This paper demonstrates the realization of an optical switch by optically manipulating a large number of polystyrene spheres contained in a capillary.The strong scattering force exerted on polystyrene spheres with a large diameter of 4.3 μm is employed to realize the switching operation.A transparent window is opened for the signal light when the polystyrene spheres originally located at the beam centre are driven out of the beam region by the strong scattering force induced by the control light.The switching dynamics under different incident powers is investigated and compared with that observed in the optical switch based on the formation of optical matter.It is found that a large extinction ratio of ～ 30 dB and fast switching-on and switching-off times can be achieved in this type of switch.     

基于叠层衍射成像的二元光学元件检测研究

本文提出了一种基于叠层衍射成像(ptychography)的二元光学元件的检测方法,该方法可实现对二元光学元件表面微观轮廓的检测以及特征尺寸的标定.相比于传统的二元光学元件检测方法,其使用无透镜成像技术,简化了系统结构并可适用于特殊环境下的检测.该方法可直接通过采集多幅衍射图,利用叠层衍射成像迭代算法可精确地复原大尺寸待测元件的表面微观轮廓,提高大尺寸器件的检测效率.本文模拟仿真了台阶高度与噪声大小对纯相位台阶板复原结果的影响,并在光学实验中选取计算全息板为样品,复原样品的表面微观轮廓信息以及得到台阶高度.以白光干涉仪检测结果为标准,该方法在精度要求不太高的前提下,可获得令人满意的成像质量.     

Observation of resonant behavior in the energy velocity of diffused light

In this Letter we demonstrate Mie resonances mediated transport of light in randomly arranged, monodisperse dielectric spheres packed at high filling fractions. By means of both static and dynamic optical experiments we show resonant behavior in the key transport parameters and, in particular, we find that the energy transport velocity, which is lower than the group velocity, also displays a resonant behavior.     

Mojette变换层析技术中的投影角度布局方法

Mojette变换是一种最小冗余采样的离散Radon变换,能够用较少角度的投影数据进行精确的计算层析(computed tomography,CT)重建,为少量投影角度CT技术的实现提供了一种新思路.投影角度的空间布局决定了层析重建最少所需投影的数量.为了获得Mojette变换层析技术中的最优投影空间角度布局方案,本文对三维Mojette变换数学模型及其精确重建条件进行了研究.以此为基础,在考虑实际探测器像素数目受限的条件下,提出了确定最优投影角度的方法.研究结果表明:所有探测器围绕被测物体在同一水平面内进行平行投影采集是最优的投影角度布局方案,此时投影模型为二维Mojette变换,所需的投影角度和探测器像素数最少,投影角度范围最小;若在实际的测量中该投影条件无法满足,则投影矢量中|pi|和|qi|的值越小越好.该研究可为实际层析系统的建立提供理论基础.     

耦合谐振器光波导旋转传感的相位灵敏度

利用光学谐振器结构的色散可提高旋转传感的灵敏度, 耦合谐振器光波导可实现强色散, 本文利用传输矩阵理论, 研究耦合谐振器光波导旋转传感的相位灵敏度, 讨论谐振器布局和波导参数对相位灵敏度的影响, 结果表明波导的相位曲线和相位灵敏度依赖于波导中谐振器的布局, 谐振器数量和耦合系数不仅会影响波导旋转传感相位灵敏度曲线峰值的数量和带宽, 还会影响相位灵敏度的大小, 而损耗会降低波导的相位灵敏度, 本文的结果可用于利用谐振器布局和波导参数设计耦合谐振器光波导的相位灵敏度, 对其在旋转传感方面的应用有重要意义. 关键词： 谐振器 旋转传感 光波导     

Cascade arrangement of irregular optical phased arrays

We present the principle of cascade arrangement of irregular optical phased arrays. The optical phased-array beam deflector comprises arrayed optical waveguides that are spaced irregularly and arranged in a two-stage cascade. Relations between optical path differences and corresponding center-to-center spacings among elements in each stage are found, and phase matches between the two stages are achieved. Simulation shows a wide scanning angle with dramatically suppressed sidelobes.     

轴向多光阱微粒捕获与实时直接观测技术

传统的光镊技术使用单个物镜同时进行光学捕获与显微成像,使得捕获与成像区域被限制在物镜焦平面附近,无法同时观察到沿光轴方向(即Z向)捕获的多个微粒.本文提出一种轴平面(XZ平面)GerchbergSaxton迭代算法来产生沿轴向分布的多光阱阵列,将轴平面成像技术与光镊结合,实现了沿轴向对二氧化硅微球的多光阱同时捕获与实时观测.通过视频分析法测量了多个二氧化硅微球在轴向光镊阵列中的布朗运动,并标定了光阱刚度.本文提出的轴向多光阱微粒捕获与实时观测技术为光学微操纵提供了一个新的观测视角和操纵方法,为生物医学、物理学等相关领域研究提供了一种新的技术手段.     

A lattice of magneto-optical and magnetic traps for cold atoms

We describe basic periodic trapping configurations for ultracold atoms above surfaces. The approach is based on a simple wire grid and can be scaled to provide large arrays of periodically arranged magnetic or magneto-optical traps. The unit cells of the trap lattices are based on crossed wire segments. By alternating the current directions in the wires of the grid it can be distinguished between 3 basic lattice configurations. As a first demonstration, we used macroscopic wires in a 2 layer configuration to realize the unit cells of the lattices. With this experimental setup, we observe two of the basic unit cells and an array of 2×2 magneto optical traps. Received 29 August 2002 / Received in final form 12 December 2002 Published online 18 February 2003