双中心全息记录的矢量分析与记录方向优化

对描述双掺杂晶体非挥发性全息记录动力学过程的Kukhtarev方程进行了矢量分析, 分析中考虑了体光生伏特效应和外加电场的作用。在小信号近似的基础上给出了双中心全息记录中记录与固定阶段空间电荷场的矢量解析解。在综合考虑空间电荷场的各向异性以及晶体有效电光系数的各向异性后, 给出了双中心全息记录的优化记录方向。结果表明, 对(Fe, Mn):LiNbO3晶体633 nm寻常光记录, 优化记录方向主要由有效电光系数决定, 光栅波矢与光轴夹角为22°, 方位角为30°;对(Fe, Mn):LiNbO3晶体633

Wideband two-port beam splitter of a binary fused-silica phase grating

The usual beam splitter of multilayer-coated film with a wideband spectrum is not easy to achieve. We describe the realization of a wideband transmission two-port beam splitter based on a binary fused-silica phase grating. To achieve high efficiency and equality in the diffracted 0th and -1st orders, the grating profile parameters are optimized using rigorous coupled-wave analysis at a wavelength of 1550 nm. Holographic recording and the inductively coupled plasma dry etching technique are used to fabricate the fused-silica beam splitter grating. The measured efficiency of (45% x 2) = 90% diffracted into the both orders can be obtained with the fabricated grating under Littrow mounting. The physical mechanism of such a wideband two-port beam splitter grating can be well explained by the modal method based on two-beam interference of the modes excited by the incident wave. With the high damage threshold, low coefficient of thermal expansion, and wideband high efficiency, the presented beam splitter etched in fused silica should be a useful optical element for a variety of practical applications. (C) 2008 Optical Society of America.

超分辨近场功能薄膜的膜层结构及其机理研究进展

超分辨近场结构光盘是最有希望达到100 GB以上的存储容量方式之一,而其记录和读出机理是研究中的重点,在近年文献研究的基础上,阐述了超分辨近场功能薄膜的膜层结构及其机理的研究进展。

A feasible approach to optical-electrical hybrid data storage using phase change material

We present our experimental results supporting optical-electrical hybrid data storage by optical recording and electrical reading using Ge2Sb2Te5as recording medium. The sheet resistance of laser- irradiated Ge2Sb2Te5. lms exhibits an abrupt change of four orders of magnitude ( from 10 7 to 10 3./ sq) with increasing laser power, current- voltage curves of the amorphous area and the laser- crystallized dots, measured by a conductive atomic force microscope ( C- AFM), show that their resistivities are 2.725 and 3.375 x 10- 3., respectively, the surface current distribution in the. lms also shows high and low resistance states. All these results suggest that the laser- recorded bit can be read electrically by measuring the change of electrical resistivity, thus making optical electrical hybrid data storage possible.

The influence of Mozart's sonata K.448 on visual attention: An ERPs study

In the present study, the effects of Mozart's sonata K.448 on voluntary and involuntary attention were investigated by recording and analyzing behavioral and event-related potentials (ERPs) data in a three-stimulus visual oddball task. P3a (related to inv

A low power integrated CMOS transmitter for BCI system

The prototype wafer of a low power integrated CMOS Transmitter for short-range biotelemetry application has been designed and fabricated, which is prospective to be implanted in the human brain to transfer the extracted neural information to the external computer. The transmitter consists of five parts, a bandgap current regulator, a ring oscillator, a buffer, a modulator and a power transistor. High integration and low power are the most distinct criteria for such an implantable integrated circuit. The post-simulation results show that under a 3.3 V power supply the transmitter provides 100.1 MHz half-wave sinusoid current signal to drive the off-chip antenna, the output peak current range is -0.155 mA similar to 1.250 mA, and on-chip static power dissipation is low to 0.374 mW. All the performances of the transmitter satisfy the demands of wireless real-time BCI system for neural signals recording and processing.

Polarization holographic high-density optical data storage in bacteriorhodopsin film

Optical films containing the genetic variant bacteriorhodopsin BR-D96N were experimentally studied in view of their properties as media for holographic storage. Different polarization recording schemes were tested and compared. The influence of the polarization states of the recording and readout waves on the retrieved diffractive image's intensity and its signal-to-noise ratio were analyzed. The experimental results showed that, compared with the other tested polarization relations during holographic recording, the discrimination between the polarization states of diffracted and scattered light is optimized with orthogonal circular polarization of the recording beams, and thus a high signal-to-noise ratio and a high diffraction efficiency are obtained. Using a He-Ne laser (633 nm, 3 mW) for recording and readout, a spatial light modulator as a data input element, and a 2D-CCD sensor for data capture in a Fourier-transform holographic setup, a storage density of 2 x 10(8) bits/cm(2) was obtained on a 60 x 42 mu m(2) area in the BR-D96N film. The readout of encoded binary data was possible with a zero-error rate at the tested storage density. (c) 2005 Optical Society of America.

Experimental study on polarization holographic storage in genetic mutant BR-D96N film

Recording with both parallel and orthogonal linearly polarized lights, polarization holographic storage in genetic mutant BR-D96N film is reported with both transmission type geometry and reflection type geometry. Polarization properties of diffraction light and scattering light are discussed for two different cases, parallel polarization recording and orthogonal polarization recording. It shows that, compared with recording with parallel polarization lights, orthogonal polarization holography can separate the diffraction light from the scattering noise, therefore improving the signal-to-noise ratio. It also shows that, compared with reconstruction with reference light, reconstruction with phase conjugated wave of the reference light can improve the signal-to-noise ratio of the reconstructed diffraction image, and also the wave-front aberration of the object light introduced by irregular phase object in the optical pass-way can also be corrected effectively, which ensures that the reconstructed diffraction image has a better fidelity. The preliminary angle-multiplexed volume holographic storage multiplexed by transmission type geometry and reflection type geometry is demonstrated in the BR-D96N film. Experiment shows that there is no cross-talk between the two pages of images except for some scattering noises.

工程地质三维建模与可视化技术应用开发

Synthetic Geology Information System (SGIS) is an important constituent part of the theory of Engineering Geomechanics Mate-Synthetic (EGMS), and is the information system more suited for the collection, storage, management, analysis and processing to the information coming from engineering geology,' geological engineering and geotechnical engineering. Its contents involve various works and methods of the investigation, design, and construction in different stages of the geological engineering. Engineering geological and three-dimensional modeling and visualization is the fundamental part of the SGIS, and is a theory, method and technique by which, adopting the computer graphics and image processing techniques, the data derived from engineering geological survey and the calculated results obtained from the geomechanical numerical simulation and analysis are converted to the graphics and images displayed on the computer screen and can be processed interactively. In this paper, the significance and realizing approaches of the three-dimensional modeling and visualization for the complex geological mass in the engineering geology are discussed and the methods of taking advantage of the interpolation and fitting for the scattered and field-surveyed data to simulate the geological layers, such as the topography and earth surface, the groundwater table and the stratum boundary, are researched into. At the mean time, in mind the characteristics of the structure of the basic data for three-dimensional modeling, its visual management can be resolved into the engineering surveyed database management module, plot parameter management module and data output module and the requirement for basic data management can be fulfilled. In the paper, the establishment and development of the three-dimensional geological information system are probed tentatively, and an instance of three-dimensional visual Engineering Distribution Information System (EDIS), theConstruction Management Information System for an airport, in which the functions, such as the real-time browse among the three-dimensional virtual-reality landscapes of the airport construction from start to finish, the information query to the airport facility and the building in the housing district and the recording and playback of the animation sets for the browse and the takeoff and landing of the planes, is developed by applying the component-mode three-dimensional virtual-reality geological information system (GIS) software development kits (SDK), so the three-dimensional visual management platform is provided for the airport construction. Moreover, in the gaper, integrated with the three-dimensional topography visualization and its application in the Sichuan-Tibet Highways, the method of the digital elevation model (DEM) data collection from the topographic maps is described, and the three-dimensional visualization and the roaming about the terrain along the highway are achieved through computer language programming. Understanding to the important role played by the varied and unique topographical condition in the gestation and germination of the highly-dense, frequently-arising and severely-endangered geological hazards can be deepened.

Absorption characteristic and nonvolatile holographic recording in LiNbO3 : Cr : Cu crystals

The absorption characteristic of lithium niobate crystals doped with chromium and copper (Cr and Cu) is investigated. We find that there are two apparent absorption bands for LiNbO3:Cr:Cu crystal doped with 0.14 wt.% Cr2O3 and 0.011 wt.% CuO; one is around 480 nm, and the other is around 660 nm. With a decrease in the doping composition of Cr and an increase in the doping composition of Cu, no apparent absorption band in the shorter wavelength range exists. The higher the doping level of Cr, the larger the absorbance around 660 nm. Although a 633 nm red light is located in the absorption band around 660 nm, the absorption at 633 nm does not help the photorefractive process; i.e., unlike other doubly doped crystals, for example, LiNbO3:Fe:Mn crystal, a nonvolatile holographic recording can be realized by a 633 nm red light as the recording light and a 390 nm UV light as the sensitizing light. For LiNbO3:Cr:Cu crystals, by changing the recording light from a 633 nm red light to a 514 nm green light, sensitizing with a 390 nm UV light and a 488 nm blue light, respectively, a nonvolatile holographic recording can be realized. Doping the appropriate Cr (for example, N-Cr = 2.795 X 10(25)m(-3) and N-Cr/N-Cu = 1) benefits the improvement of holographic recording properties. (c) 2005 Optical Society of America.

Refractive-index change and sensitivity improvement in holographic recording in LiNbO3:Ce:Cu crystals with green light

Nonvolatile holographic recording is performed with green light in LiNbO3:Ce:Cu crystals. The refractive-index change and the recording sensitivity are times better than those obtained by recording with red light, and higher optical fixing efficiency is obtained. Correspondingly, theoretical investigations are given.

Vectorial solution of Kukhtarev equations for doubly doped crystals and optimal choice of recording directions in nonvolatile holographic storage

Vectorial Kukhtarev equations modified for the nonvolatile holographic recording in doubly doped crystals are analyzed, in which the bulk photovoltaic effect and the external electrical field are both considered. On the basis of small modulation approximation, both the analytic solution to the space-charge field with time in the recording phase and in the readout phase are deduced. The analytic solutions can be easily simplified to adapt the one-center model, and they have the same analytic expressions given those when the grating vector is along the optical axis. Based on the vectorial analyses of the band transport model an optimal recording direction is given to maximize the refractive index change in doubly doped LiNbO3:Fe: Mn crystals. (c) 2007 Optical Society of America.

Optical near-field simulation of Sb thin film thermal lens and its application in optical recording

Using the finite-difference-time-domain method, the near-field optical distribution and properties of Sb thin film thermal lens are calculated and simulated. The results show as follows. Within the near-field distance to the output plane of thermal lens, the spot size is approximately 100 nm, and its intensity is greatly enhanced, which is higher than that of incident light. The spot shape gradually changes from ellipse to round at the distance of more than 12 nm to the output plane. The above-simulated results are further demonstrated by the static optical recording experiment. (C) 2005 American Institute of Physics.

Optical parameters and absorption of copper (II)-azo complexes thin films as optical recording media

Smooth thin films of three kinds of azo dyes of 2-(5'-tert-butyl-3'-azoxylisoxazole)-1, 3-diketones and their copper (II)-azo complexes were prepared by the spin-coating method. Absorption spectra of the thin films on a glass substrate in the 300-600 nm wavelength region were measured. Optical constants (complex refractive index N=n+ik) and thickness of the thin films prepared on single-crystal silicon substrate in the 300-600 nm wavelength region were investigated on rotating analyzer-polarizer type of scanning ellipsometer, and dielectric constants epsilon(epsilon=epsilon(1)+i epsilon(2)), absorption coefficients alpha as well as reflectance R of thin films were then calculated. In addition, one of the copper (II)-azo complex thin film prepared on glass substrate with an Ag reflective layer was also studied by atomic force microscopy (AFM) and static optical recording. AFM study shows that the copper (II)-azo complex thin film is very smooth and has a root mean square surface roughness of 1.89 nm. Static optical recording shows that the recording marks on the copper (II)-azo complex thin film are very clear and circular, and the size of the minimal recording marks can reach 200 nm. (c) 2004 Elsevier B.V. All rights reserved.

A new photopolymerizable holographic recording material based on acrylamide and N-hydroxymethyl acrylamide

A new polyvinylalcohol-based photopolymeric holographic recording material has been developed. The recording is obtained by the copolymerization of acrylamide and N-hydroxymethyl acrylamide. Diffraction efficiencies near 50% are obtained with energetic exposure of 80mJ/cm(2). N-hydroxymethyl acrylamide can improve the optical quality of the film. With the increase of the concentration of N-hydroxymethyl acrylamide, the flatness of the film increases, scattering reduces and the straight image is clearer with a small distortion. The postexposure effect on the grating is also studied. The diffraction efficiency of grating increases further during postexposure, gradient of monomer exists after exposure.