In this paper, we propose a novel method of three dimensional optical storage by the use of multilayered waveguide memory (MWM). The MWM structure is described and its work principle is introduced. Some properties and merits of MWM are also discussed in comparison with other 3D optical data storage methods.

In order to increase the efficiency of information utility in the digital holographic storage system, we designed and implemented a novel Modulation-Array code and the corresponding decoding algorithm. The results of preliminary experiments with holographic data storage are satisfactory.

Ce:Co:SBN, Ce:SBN and Co:SBN crystals have been grown by Czochralski method with CeO₂ and Co₃O₄ as dopants in air atmosphere. With these crystals as holographic storage media, the diffraction efficiency, response time and phase conjugate reflectivity are measured. The Ce:Co:SBN crystal exhibits better properties than SBN crystal and especially its diffraction efficiency is up to 70%. The Ce:Co:SBN crystal is used as holographic storage media to realize highly effective association storage in four-wave-mixing-frequency path with Zn:Fe:LiNbO₃ crystal as feedback threshold element.

This kind of plate that has an imaging layer, comprising an admixture of (1) a resole resin, (2) a novolac resin, (3) a latent Bronsted acid (4) an infrared absorber, and (5) colorant, relates to an image recording material which can be used as a material for a lithographic printing plate. The radiation-sensitive composition is sensitive to both ultraviolet and infrared radiation. The plate is intended for digital exposure with an infrared laser with 830 nm in a computer to plate (CTP) machine. The dot density of the printing plate ranges from 2 to 98 percent, and the resolution can reach 6μ. On the aspect of making printing plate these characteristics achieve acceptance criterion of printing. In addition, the level of laser energy needed to image a thermal plate is substantially higher than that needed to image today's conventional plates.

We have investigated the characteristics of thermal fixing holograms in batch. The loss of signal-to-noise ratio (LSNR) is used in comparing the noise performance of hologram before and after each batch of thermal fixing. The experiment results on batch fixing show that the deterioration in hologram fidelity is mainly caused in recording phase at the room temperature, and the repeated fixing processes won't further produce significant noise to degrade holograms.

Optical Disk Cluster (ODC) drive is the key component of ultra-large capacity optical storage system. The principle of ODC drive is introduced. The measurement and analysis system of dynamic properties of ODC is developed using graphical programming language, LabVIEW, the best software platform of virtual Instruments. The vibration characteristic of ODC is studied. The experiments show that the main reasons of ODC vibration are shaft eccentricity, disalignment of shaft, and inclination of optical disk. As the result, the methods of reducing vibration of optical disk are presented, which can be used to optimizing design of ODC.

An m:n binary constant weight modulation code (BCWMC) can simplify signal decision and improve bit-error rate (BER) performance in holographic digital data storage. Computer simulations results show that different mapping patterns onto a spatial light modulator (SLM) cause different BER performance for the same code word length of a BCWMC on a severe two-dimensional (2-D) inter-symbol interference (ISI) channel with additive white Gaussian noise (AWGN). We employ two of self-definition, the adjacent degree of a pixel array (ADPA) and the degree of deflective center (DDC), to explain the reason. The calculations by the two of self-definition are in line with the simulations.

The use of multiple data layers has been an effective way to increase the capacity of an optical disk. In particular, the dual-layer approach has been used successfully to double the capacity of a DVD-ROM disk as compared to its single-layer counterpart. In the design of such a dual-layer disk, the existence of the crosstalks between the signals received from the two data layers is an important system design constraint. In this paper, the optimization of the crosstalks is investigated by treating the reflectance of the semi-reflective layer and the reflective layer as free design parameters. It is shown that it is not possible to simultaneously minimize the crosstalks that arise, respectively, from reading the first data layer and from reading the second data layer. On the other hand, it is shown that it is possible to simultaneously equalize the crosstalks and the signal-to-noise ratios by an appropriate choice of the reflectance of the semi-reflective layer and the reflective layer. Numerical results obtained from this study agree well with experimental results.

In order to meet the requirement for an ultrahigh data transfer rate in future optical communication systems, a parallel optical memory system has been developed using a VCSEL array and three-dimensional microoptical adjustment. The concept, theoretical analysis and fabrication process for the array head are discussed with emphasis on the microoptical issues such as the improvement of optical efficiency by surface plasmon enhancement and microlens focusing. The flat-tip microprobe structure was successfully prepared with the small metal aperture of 150 nm and 1.25% optical throughput using metal-aperture Si or GaP semiconductor microprobes. From the finite difference time domain (FDTD) simulation, the optical throughput can be improved using a buried-type microprobe with an asymmetric metal-coated structure since this is a better structure for improving coupling efficiency between the propagating wave and surface plasmon. Since the focused beam promotes better optical throughput in the integrated VCSEL microprobe array, the microlens array is developed on the other side of the microprobe array using the thermal Reflow of photo-resist and a pattern transfer process to the semiconductor substrate. The alignment of optical axis between the optical components is critical to achieving the required optical efficiency in this system. Thus, three-dimensional micro-optical adjustment is being studied to focus a very small spot on the recording media. This three-dimensional approach will provide guidelines for new micro-optical components in future technology in the field of optical memory and other micro-optical systems.

Next generation of optical storage will use shorter wavelength lasers and higher NA lens to achieve large capacity and high density. But with increasing NA and decreasing wavelength, the depth of focus decreases rapidly. We describe a technique to get smaller width focus spot and longer depth of focus by shaping a focused Gaussian beam. The important feature of the filters is their simplicty. The apodization can be used for applications such as blue-ray optical data storage, super-REN storage and mastering.

The characteristic parameters of focusing and tracking servo systems have an important influence on the control accuracy. Among these parameters, those related to DVD optical pickups should be taken more account before designing servo control algorithm and Jitter is a key parameter to evaluate the comprehensive properties of DVD servo systems. This paper analyzes their influences on DVD servo system, discusses the evaluation and test methods of some key parameters according to actual testing results.

AgOx thin-films were studied by using an optical read-write-tester. Two different states were found by CCD and SEM images, and the optical properties were examined by the pump-probe technique. A scattering center was found in the AgOx thin film. The enhanced reflectance was due to strongly local scattering and plasmon excitations.

The photochromic retinal protein bacteriorhodopsin (BR) modified by genetic method is considered as a promising material for optical and holographic recording because of its effective photochemistry, high stability and unique reversibility. The parallel image recording can largely increase the speed of data writing and reading in comparison with the bit-type recording. Here, we established a micro-imaging system with BR-D96N biofilm as recording medium. The optical image loaded on a LCSLM was illuminated by an argon laser (514 nm) and was micro-imaged on the BR film with a high resolution lens. The BR film was mounted in a two dimensional micropositioning system for accurately addressing. The recorded images were readout by a CCD camera under weak illumination of 514 nm laser. In this system, we can record 1000 frames of microimages on the BR film with each frame having an area of 460μm × 350μm. This system can be developed into a two dimensional parallel digital optical data storage setup.

The very small aperture laser (VSAL) is an important light source used in the near-field optical storage system. It is necessary for studying the near-field property of VSAL's output light. The optical characters and the intensity distribution in the near-field of the output region of the VSAL have been numerical simulated using two dimension nonlinear FDTD (2D-NL-FDTD) method and the Fox-Li method. Through analyzing the results from the viewpoint of the Optics, the possible application in the near-field optical recording have been discussed, and some curves indicating the near-field optical characters of the output light have been presented.

ACT is the key components on the CD/DVD optical pickup, and is the precision servo-mechanism which can realize focusing and tracking of high-resolution ratio. Its characteristics (static & dynamic characteristics) is directly related with the quality of the CD/DVD optical pickup. This paper presents a new testing method & device for the characteristics of ACT based on VI & fiber optics sensors. The method & device can be used for testing the sensitivity (static characteristics) and frequency respond (dynamic characteristics) of ACT on the CD/DVD optical pickup.

Scratches are common defects on the surface of optical disks and affect the status of the servo system and the readout of data, sometimes they even cause the breakdown of the system. To understand the mechanism, it is necessary to investigate profiles of scratches and their influence on the servo system and the HF signal. In this paper, the 3D profiles of more than 15 scratches have been measured, and the scratches are defined as U-type, W-type and M-type respectively. The experiments show that the rough surfaces of scratches scatter away the incident light heavily, and finally reduce the light intensity and change the intensity distribution on the exit pupil plane. The influences of the U-type scratch, W-type scratch and the M-type scratch on a servo system and HF signal are discussed.

Three-dimensional optical memory with photorefractive materials is discussed for ultra-high density/capacity memory exceeding the classical limit of a conventional optical recording system. Bit data are recorded as highly localized refractive index variations in three-dimensional volume using a focused laser beam. We show recording and reading results using various recording materials and optical configurations. A multi-structured optical recording medium using a photoisomerization polymer and a transparent films has been developed for reflection confocal reading. Two-photon recording is also demonstrated.

An optimum design scheme for a new 3 Dimensions Magneto-Optical Disc information storage system is proposed. By the use of the Polarization Preserving Fiber (P.P.F) integrated opitcal head, the small objective lens of the P.P.Fiber optical head can be moving at high speed, the average access time of the storage system can be reduced effectively. The wave division multiple technology can be used to realize multi-wavelengths optical fiber signals transmission in parallel mode, so the 3 dimensions storage system possesses the advantages of huge density, and the access time will be further decreased. According to the laser diffraction theory, an optical expert system software is set up to analyze the aberrations of the integrate optical head, and to compute the pick-up signals by computer simulation.

Most photopolymer materials consist of a photopolymerizable monomer, a photoinitiator and a sensitizer in a polymer binder. During optical exposure, a few photons can initiate a chain reaction of photopolymerizable monomer molecules, which cause a change of the refractive index, forming hologram. In tradition, the refractive index of the monomer is higher than that of the binder, and the magitude of the refractive index modualtion is dependent on the differnce in refractive indices between the binder and the monomer. A novel photopolymer material different from the tradition is presented in this paper, in which the monomer is MMA with the refractive index much lower than that of the binder synthesized from epoxy resin monomer and XDA, so that the material can be conveniently developed into samples with dimension stability and high optical quality and thickness of several millimeters or more. A holographic recoridng medium of 0.8 mm thickness has been fabricated, and the storage characterizations as well as its relative theoretical analysis of its are presented.

In volume holographic data storage systems, there are brightness variations across the detected image. An incorrect choice of the threshold can cause significant degradation in the BER. Therefore various modulation codes, including global threshold, local threshold, and equal-weight modulation codes, are proposed for volume holographic data storage systems to improve performance by providing their advantages at the decision stage. Considering about our target and the properties of our holographic data storage system, we select a modulation code for our system and realize it.

Chiropticenes^TMare a novel class of designer molecular switch materials, which are triggered by a combination of both light and electric field. Chiropticenes contain an optically active (chiral) center and as a consequence provide two accessible equal energy states resembling the molecular elements of binary logic. Functioning as a chiroptical dipole switch, Chiropticenes promise broad applications in emerging optoelectronic and molecular electronic technologies. A synthetic protocol for the preparation of Anthraquinone dye based Chiropticenes is presented and their thermal/optical switching behavior in solid state is described.

Near-field optical recording based on solid immersion lens (SIL) system has attracted great attention in the field of high-density data storage in recent years. The diffraction limited spot size in optical recording and lithography can be decreased by utilizing the SIL. The SIL near-field optical storage has advantages of high density, mass storage capacity and compatibility with many technologies well developed. We have set up a SIL near-field static recording system. The recording medium is placed on a 3-D scanning stage with the scanning range of 70×70×70μm and positioning accuracy of sub-nanometer, which will ensure the rigorous separation control in SIL system and the precision motion of the recording medium. The SIL is mounted on an inverted microscope. The focusing between long working distance objective and SIL can be monitored and observed by the CCD camera and eyes. Readout signal can be collected by a detector. Some experiments have been performed based on the SIL near-field recording system. The attempt of the near-field recording on photochromic medium has been made and the resolution improvement of the SIL has been presented. The influence factors in SIL near-field recording system are also discussed in the paper.

The photorefractive effect in Indium-doped litium niobate crystal was studied. We found that the enhanced photorefractive sensitivity could be realized in the so-called photorefractive resistance lithium niobate crystals, even higher than the well-known iron doped ones. We explained the unusual qualitatively. The experimental result enriches us the knowledge of the properties of doped lithium niobate crystals and provides some advice in growing specific crystal.

In this paper, the pupil energy distribution is calculated with parameters of digital versatile disk and by using the scalar diffraction theory. In view of radial tilt, a radial tilt angle in pit model is added, and consequently, a simulation of push-pull tracking error is given when a radial tilt error occurs. Furthermore, the influence of radial tilt is analyzed by using push-pull tracking servo method.

A new azo nickel chelate thin film has been developed for short wavelength write-once optical recording by a spin-coating process. Thermal property of the dye was studied by thermo-gravimetric analyzer (TGA). The azo nickel chelate begins to decompose at temperature 295.6°C, which is 44°C above that of azo, and rapidly decomposes in the narrow temperature range. A dynamic optical recording test on the disc made of this dye indicated that the CNR of written signals was more than 43dB at low writing power and short writing pulse-width using Ar⁺ laser (514 nm) irradiation in a wide scan velocity range.

Third-order nonlinear optical properties of cover glass coated with different metal films are studied by using a focused pulse laser (λ=532 nm, pulse width 0.7ns, repetition rate 15.79kHz) with a Z-scan system. The results of open-aperture mode Z-scan shows high transmittance in the AgOx sample. The enhanced third-order nonlinear coefficients were examined by close-aperture mode Z-scan. The plasmon excitation and thermal relaxation were discussed for experimental results.

Multi-wavelength photochromic storage is a new optical storage method based on the photochromic principle. Experiments are carried out on 3 materials to test their sensitivity, crosstalk and operating time. One material of them is sensitive to lasers of 780 nm; the other, 650 nm and the last, 532 nm. The experimental results show: the three photochromic materials are all sensitive enough to record data. The crosstalk of 650 nm and 532 nm materials is neglectable, and they can be used in multi-wavelength optical storage as new photochromic materials. But the 780 nm material is also sensitive to 650 nm laser, and it results in obvious crosstalk. Therefore, the 780 nm material can't be of use only if it's improved greatly.

A dual-laser DVR system, which utilizes chromatic aberration to obtain dual-layer storage, is reported in this paper. A non-achromatic objective lens is used, which is especially designed. It focuses 405 nm laser and 440 nm laser on two recording layers of the disc. Parallel accessing is avaialble to incrase data rate. Another key problem of the system is how to achieve space layer with high thickness stability. Some key problems of this system are discussed, such as: disc structure, writing and reading strategy, etc.

The optical non-linearity property of the Sb sandwiched structure was studied under the static condition via several experiments. The non-linearity effects of this sandwiched structure were clearly observed. And a primary explaining was given on the base of the experiment results. Conclusively, the optical non-linearity property of the Sb sandwiched structure is obvious. With this structure, the radius of the focused laser beam can be reduced effectively, almost 35% to approximately 50%. And the effect of this structure is not only the radius reducing of the focused laser beam, but also the increasing of power density. This phenomenon suits the analysis of energy localization in theory well.

The X-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES) were used to analysis the chemical composition and valence of sputtered electrochromic nickel oxide films is as-deposited, fully bleached and colored states. Experimental results showed that no Ni(OH)₂ exists in these three states. Potassium adsorbs at the NiO film surface instead of entering the lattice of nickel vacancies when the nickel oxide films were coloring/bleaching cycled in KOH solution. And the chemical valence of Ni does not seem to change after coloring and bleaching. A new electrochromism for sputtered nickel oxide films in aqueous electrolytes is proposed.

This paper targets the optimum solution of storage and management of digital media assets. We present a media assets management system with distributed architecture to achieve good performance in an economical way.

We investigated the infrared spectra of the optical damage caused by laser diode at 808 nm in iron-doped lithium niobate crystals. The spectra show that the OH⁻ absorption band in the region of the optical damage exhibits a structure consisting of three peaks. Comparing to the spectra at the non-damage region the main peak moves to red. The result will be helpful to microphotonic device applications.

Fiber Channel, a new interconnect technology for high-performance computer peripherals and storage devices, has been developed and widely used in the field of large-volume optical storage systems. This paper presents an approach of high-speed sustained data transmission system based on Fiber Channel, in which real-time requirement and low-latency are two key points. This system can transfer high-speed data stream from the source to the host over Fiber Channel. The hardware structure and software design are given in this paper. Furthermore the improvement of capability and reliability of large-volume optical storage system using Fiber Channel is put forward.

The diffraction theory, which includes scalar and vector diffraction theory, is an important basal theory in the field of optical storage. The purpose of this paper is to analyze the needs of using vector diffraction theory instead of scalar diffraction theory in the study of the digital versatile disk (DVD) or other high-density optical disks, and summarizes the effects of the optical disk pattern parameters on the readout signals. The grating is adopted as the physical model of optical disk in this research. And the readout signals are calculated only versus some parameters, involving the transverse dimensions, the depths and the slopes, of the information marks with vector diffraction theory. Accordingly some key factors to guarantee the optical disk manufacture quality are put forward, and these factors resulted from this study may be useful to improve the optical disk manufacture technica, furthermore, the vector analysis methods adopted herein are referable to higher density optical storage research.

With the increasing demand of optical storage capacity, multi-level (ML) optical storage based on multi-level-amplitude modulation is receiving more and more attention, for it transmits more information ove a fixed bandwidth channel by using the available SNR more efficiently. We proposed an ML optical storage technology in azo LCP film based on polarization angle division. In this paper, the write strategy is developed by a ML write-compensation system that corrects for non-linearities of the data signal. The dynamic transmittance range is extended with the full monotonic range of angle and the varaition of each amplitude level relative to our dynamic range is improved. The experiments of imroved linear and nonlinear 16-level storage in azo LCP are demonstrated. The effects of thickness non-uniformity on linear and nonlinear 16-level storage are discussed.

Photon-mode recording of photochromic materials is regarded as a promising storage system, which has various advantages over the traditional heat-mode recording in terms of its data capacity and data-recording rate. Diarylethenes show good thermal stability and remarkable fatigue resistance, and these properties are indispensable for the applications to optical storage materials. In present work, several diarylethene compounds were synthesized, and a series of optical storage tests were carried out on the sample discs with diarylethenes as the recording materials. The recording based on these photochromic materials was photon-type,and the recorded regions appeared as faded dots. 780, 650 and 532 nm lasers were used for writing on the corresponding discs, and the recorded information were readout by the same lasers respectively. A two-wavelength optical storage was realized on a mixed diarylethene recording layer by two laser beams of 532 nm and 650 nm synchronously. A higher data capacity can thus be expected to reach by using a multi-wavelength optical storage like that. Although the diarylethenes satisfy the minimum demands of optical storage systems, these molecules have one unsolved drawback: the lack of a non-destructive capability. In this work, Electric-locked properties were investigated in a BT3FP-OH thin film; the electric trigger could prevent the photochromic reactions, which provided a practicable non-destructive readout method. Three kinds of diarylethene derivatives linked by solvatochromic dye units wer fabricated; the theoretical investigation showed that reading at the wavelength of about 650-750 nm would destroy the recorded information no longer. Thus a non-destructive method could be constructed on these diarylethene molecules.

Based on theory and method of the near-field optics, optical resolution of near-field scanning optical microscopy (NSOM) is beyond the classical optical diffraction limit and down to tens of nanometer or even less. In this paper, a collection mode NSOM is built to detect and analyze local near-field distribution. The output optical field of a standard 1μm×1μm scale 2D grating has been detected. This NSOM system can also be used to study local near-field distribution of the focused spot of solid immerging lens (SIL) and the result can be directly used to evaluate SIL and compared with the calculation of its theoretical model and as a result, to improve the theoretical model.

In this paper a Cu:Fe:LiNbO₃ crystal is chosen to be the recording material with the gating light of 355 nm pulsed laser and the writing light of 633 nm He-Ne laser. We investigate the effect of the pulsed UV pre-exposure on the writing time constant, the achieved maximum refractive-index modulation and writing sensitivity of the crystal.

As the error probability is inherently high in the high-density optical storage system, it is very important to encode the data to ensure the data integrality before recording them on the disc. As the performance of the Reed-Solomon (RS) code is perfect for the applications where burst errors and random errors exist together, RS code is adopted as the error control scheme in our design of the multi-wavelength optical storage system. Since field programmable gate array (FPGA) is reconfigurable, the FPGA-based encoding circuit in the multi-wavelength optical storage system provides a flexible and cost efficient platform for the evaluation and verification of various error control schemes. The design and implementation of RS codes on FPGA are presented in this paper. The experiment result shows that it is practical to be used in the multi-wavelength optical storage system.

The write strategy of the phase-change optical disk determines its read-out performance, and optimizing the write strategy is an important step of the recording process on the disk. The action on the phase-change material from the laser comes down to the thermal effect of the laser. In this paper, the temperature rise curves under different write strategies have been discussed at the aspect of thermal modal, and the optimum write strategy is brought forward, which could direct the actual write process design.

MultiLevel encoding has been demonstrated to significantly increase the linear densities achieved with standard methods of binary encoding in optical data storage systems. An overview of the channel is provided from write encoder and pre-compensation, to readout with a matched adaptive equalizer and Viterbi decoder. Our multilevel channel has been implemented in silicon and designed to operate in parallel with the standard binary channel, thus maintaining full backward functionality of the underlying drive. We have developed an efficient research, development, prototyping, and integration process that allows us to accomplish final system implementation with minimal impact to the host system. We discuss our "helper" servo and firmware functions that ease integration of the multilevel LSI into existing circuit-board architecture, firmware, and software bases. The focus of this paper is on our fully-functional 2GB enhanced CD-R/RW external drive, but we also discuss briefly how multilevel technology has been shown to add to ROM, DVD, and advanced blue-laser, high-NA optic systems.

Two-photon single beam multi-layer writing and scanning confocal reading are performed in anthracene derivatives membrane by Ti:sapphire femtosecond laser and three-dimensional scanning confocal system. And a good result is achieved, Two-photon excitation can be produced inside the anthracene derivatives membrane, where is 100 μm from the surface of the recording material. The wavelength of the laser is 726 nm(363nm×2). The size of recording spot along longitidunal direction is less than 2 μm, and that along lateral direction is less than 1 μm. The signal keeps clear definition after many times of reading out, when the power of the reading laser is less than 5 mW.

A network-attached CD Image file server, working on the Linux operating system, is implemented. By taking advantage of virtual file system (VFS) infrastructure and loopback device, the data of CD are mirrored in harddisks and can be shared by clients synchronously through network. The primary benefits of such a server are cost effectiveness, high capacity and excellent compatibility with Chinese characters. The performance of the server is evaluated by testing its throughput during I/O request. The experimental results show that, compared with conventional methods such as sharing the CD-ROM hard devices via network as, the rate of reading data from the CD Image is much higher. This is especially true when the server is dealing with multi-client access.

In normal angular multiplexed holographic storage system, to make the system compact, replacing the Ar⁺ laser with the diode-pumped solid-state laser (DPL) is an important means, but the application of DPL will increase the cross-talk and reduce the storage density because of the multiple longitudinal modes in the output of the DPL. In this paper, a novel speckle holographic storage scheme is proposed, in which a random phase diffuser is added in the front of storage medium along the reference optical path of the 90° geometry. A theoretical model has been derived to describe the storage properties of this scheme based on the cross-correlation of dynamic speckle and the diffractive theory. The angular selectivity in the normal angular multiplexed system and in the speckle-coded angular multiplexed system have been theoretically compared and experimentally confirmed. The results indicate that this scheme allows an increase of storage density with a simple modification in the DPL system.

By using Sb as the super-resolution reflective layer and the SiN as dielectric layer, the super-resolution pits with a diameter of 380 nm were read out by the readout optics system with a laser wavelength of 632.8 nm and a NA of 0.40. In addition, the influence of the Sb thin film thickness on the readout signal was investigated, the results showed that the optimum Sb thin film thickness is 28 to approximatley 30 nm, and the maximum CNR is 38 to approximately 40 dB.

A theoretical model for CD-R dye coating on a substrate with spiral pre-groove is presented. A typical CD-R dye coating process consists of three stages: dispensing stage, spreading stage and vaporizing stage. Some assumptions and simplification for every stage are made and the second stage is mainly analyzed. The motion equation, boundary equations and continuity equation of flow for dye film are derived, taking into account topography on substrate and interface slip between liquid and substrate. Finally the governing equation is given.

An experiment on the character of photochromic recording material is introduced. Numerical method is used to describe the material character. Based on it, the multi-level experiment demonstrates the availability using photochromic material as recoding medium of 4-level storage system. Finally, a further analysis on optimizing the exposal parameters of different levels of multi-level disc is presented.

The principle of multi color storage using 3 lasers with different wavelength is introduced and the Method of Three-wavelength Confocal Adjustment (MTCA) is represented in detail. The three lasers are combined into a coaxial paralleled laser beam after passing through their own collimation system and one common light coupling system. Then they are focused in the same spot on the recording layer by an achromatic lens. The defocusing amounts' measurement bases on the knife-edge displacement method and displacement method of optoelectric detector. And then the 3 lasers can read and write confocally in recording media.

An experiment for focusing in chromatic multilayer optical storage system is presented in this paper. There laser diodes with different wavelength as respectively light sources are used in this experiment system so that focusing and servo approach are different from that in traditional optical system. Astigmatic approach is applied for defocusing detection while servo controlling and signal processing circuits are redesigned. The model of the actuator suited this chromatic multilayer optical system is established and analyzed. The static and dynamic parameters of actuator are measured. This paper specifies the design and implementation technologies of focusing and servo controlling in the chromatic multilayer experiment optical system. The preliminary result gotten from this experiment system is also given in the paper.

The advanced data storage technology is important to information era. Among all sorts of solutions of high-density storage, near field optical disc technology (NFOD) is high speed and mass storage technology with excellent aptitude and future, and it is the focus of data storage research field in the pioneer technology. Today the research institutes all over the world are speeding their research on NFOD. By using the techniques of solid immersion lens (SIL) and super-low-flying system, it can achieve not only super-high recording density that can be much more higher than traditional optical disks but also the hard disks. In order to improving near-field coupling efficiency of SIL-TO-DISK, the SIL must keep sub micron flying height from the disk, so it is necessary to discuss the research process of real time method to measure SIL-TO-DISK for super-low-flying system. This paper analyses technique foundation and characteristc and its key problem for the flying height measurement, the paper studies several practicing plan of real time measure the clearance even when the SIL-DISK spacing is down to nanometer level for example, relative light intensity method, the capacitance displacement sensors, effective refractive index method for frustrated total reflection, and compare the characteristic and precision of those approach.

A newly developed device using organic dye-polymer systems (DPS) has been shown to be remarkable photosensitive media for volumetric data storage. Based on two-photon absorption, data could be 'bit-by-bit' written in and florescent 'page-by-page' read out both by single beams at different wavelengths. Key technologies and industrial application are discussed.

Based on the coupled wave theory, the cross-talk noise in fractal multiplexed volume hologram is analyzed. The simulation of the reconstruction of a single hologram under conditions of different deflecting angles and pitching angles of read-out reference beam is made, experiment result is presented, and a 2D figure of cross-talk noise distribution is given. The analysis and the experiment result confirm that the read-out of spectrum hologram under changed pitching angle will appear as a horizontal strip, and the strip will move vertically with the change of deflecting angle.

One way of achieving super-resolution is to convert the Guess distribution of the object space into square distribution of that. A special phase-shifting lens is designed for attaining the function. In developing designs for the special phase-shifting lens, algebraic approximate formulas are used to obtain a general understanding of the transition between the Guess distribution and the square distribution. Computer simulation was then used to obtain a detailed performance evaluation. The evaluation results indicated the following: the Guess distribution of the laser light is converted into the square distribution by the special phase-shifting lens.

Recording experiments on Super-RENS mask were done for color (multi-wavelength digital data storage at various recording conditions.Through SEM, the recording marks were found reduced down notably. These micrograms were studied fully, and the results forcefully demonstrate the super-resolution recording effect in Super-RENS.

For the application of volume holographic storage with large capacity and high density, the performance of Zn:Fe:LiNbO₃ crystal is studied. Through the study of the absorption spectra and the diffractive efficiency curve of samples with various doping concentrations and oxidation/reduction treatment, some important properties are derived and analyzed in this paper. We find that Zn:Fe:LiNbO₃ crystal has better performance for volume holographic stroage, such as high diffractive efficiency, short response time, broad angle range for multiplexing, and high photo-scattering resistance. The recording schedule for multiplexing holograms with equal diffractive efficiency is also deduced. On the basis of these results, five hundred volume holographic pages, each containing 1024×768 pixels and having same diffractive efficiency, are stored and read out in a common volume of Zn:Fe:LiNbO₃ by using the 90° geometry and angle multiplexing. By improving the multiplexing technology and choosing proper samples, we can realize larger capacity and higher density.

The volume holographic optical data storage has been an important and exciting area of research on account of its promising super high density and fast data transfer rate. Recently, much attention has been paid to the novel speckle multiplexing, which has the potential of increasing the current storage density prominently. As is well known, cross talk between holographic gratings is a vital factor that may influence the storage density of hologram. In this paper, we analyzed the cross talk of the speckle-angular multiplexing scheme, in which a random diffuser is added in the front of storage medium along the reference optical path of the original 90-degree storage geometry. And compared it with that of the original angular multiplexing scheme, both theoretically and experimentally. The results indicate that this novel scheme could not only increase the storage density but also decrease the cross talks in the system.

Multi-wavelength photochromic storage is a new optical storage method based on the photochromic principle. In this paper, the storage method itself and the mathematic model developed to describe the change of the reflectance in the writing process are discussed. For the photochromic materials, which are sensitive to 650 nm and 532 nm laser respectively and mixed into one layer, the reflectance of the readout laser in the writing process was measured with a 3-wavelength photochromic storage system. The theoretical results of the model agree well with the experimental ones. It is also found that the photochromic optical storage has no threshold.

A novel storage system is introduced which bases on the "multilayer multilevel storage model." Three kinds of lasers that are different in wavelength are used to record data or test some storage material in this system. An example that is testing the photochromic material is also introduced to explain the usage of the system in testing storage material.

Holograms are recorded in near-stoichiometric LiNbO₃ doped with 8 ppm of Mn by use of two-color holographic recording method, where an IR laser of 778 nm is used for writing and an UV laser of 350 nm is used for gating. Dependences of two-color sensitivity and M/# on gating and writing intensities are presented. Significant improvements of sensitivity, M/# and dark decay are obtained compared with reduced near-stoichiometric LiNbO₃. To our knowledge, the measured two-color sensitivity of 0.21 cm/J with a gating intensity of 1.5 W/cm² is the highest among the values reported so far, which is attributed to large light-induced absorption of small polarons. 50 plane-wave holograms are recorded by the conventional angle-multiplexing method.

Two-color recording is achieved in a Tb-doped near-stoichiometric LiNbO₃ crystal of 3-mm thickness by use of extraordinary 778 nm information-carrying beams and ordinary 350 nm gating light. The dependences of key parameters, the two-color recording sensitivity and the dynamic range expressed by the saturated diffraction efficiency, on intensities of recording and gating beams are presented. The saturated diffraction efficiency increases with total writing intensity, and then reaches a saturated value of 56% at an intensity of 20W/cm². The sensitivity increases linearly with gating intensity at low intensity, and then saturates with a value of 0.08 cm/J at a higher intensity than 1.6 W/cm². The saturated sensitivity is much higher than the reported value in literature. This material shows very significant improvement on two-color holography performance. 50 plane-wave holograms are recorded by the angle-multiplexing method and an M/# of 1.13 is obtained.

In this paper, we propose a photorefractive disk-type memory with cross polarized four-wave mixing, and suggest a method to enhance the storage density for this disk-type memory. The shift multiplexing technique, in which the feasible recording of the angularly multiplexed holograms can be implemented by means of the spherical reference beam and the rotation of the disk-shaped crystal, is applied for this memory. We analytically investigate the amounts of shift required for multiplexing differential holograms in this memory, and we carry out an experiment to verify the analytical results. Also we suggest a logical multilayer recording method as the novel scheduled recording method, and analyze the temporal property of cross polarized four-wave mixing to estimate the diffraction efficiencies from the multiplexed holograms with the method. From those analyses, it is revealed that the diffraction efficiency and the storage density of the photorefractive disk-type memory are significantly improved by this method.

We propose an all-optical encryption memory using the photorefractive four wave mixing and random phase masks. In our encryption method, the image data are encrypted to white noise by the phase shift patterns added on the signal beam with the image data and the reference beam through the random phase masks. Only reading beam with the phase-conjugated distribution of the reference beam can restore the encrypted data. If the encrypted data are read out by incorrect phase pattern, the output data can't be obtained because of the wavefront mismatch between the recorded hologram and the reading beam. We evaluate the encryption and decryption process by analyzing the diffraction efficiency with consideration of the angular spectrum. We show that high performance encryption that high contrast and high gradation image data can be decrypted accurately and the output data are perfectly dark by using the incorrect decryption key can be realized theoretically.

Tolerance analysis for focusing unit of near field recording system is presented. The assembling and manufacturing tolerances of SIL and OL are simulated using CODE V. In addition, we proposed to move collimated lens (CL) back and forth to compensate and control these tolerances, especially in optical axis direction. And we proposed, a new doublet solid immersion lens (DSIL) for near field optical system, which can minimize the tilting, decenter, defocus misalignment problems between objective lens and solid immersion lens in existing near field optical system. The objective lens, which confines the beam, and secondary lens which increases the numerical aperture, join together to make one module cemented lens system.

The use of Ge-Sb-Te films for rewritable optical storage is based on the reversible phase change between their amorphous and crystalline states. Study of the crystallization behavior of the films is very necessary to the optimization of film composition and dopants. This work dedicates our experimental investigation on the crystallization behavior of oxygen-doped Ge-Sb-Te phase change films, which were prepared by RF-sputtering. The crystallization behavior of the thin films was investigated using differential scanning calorimeter (DSC). XRD spectra of the films in the as-deposited and heat-treated states show that the films changed from amorphous to crystalline states due to heat-treatment. By measuring the peak temperature of crystallization at different heating rates we calculated the crystallization activation energies and frequency factors. It was found that the oxygen-doped Ge-Sb-Te sample has a higher value of crystallization activation energy than that without oxygen-doping, it is clear that oxygen-doping can improve the crystallization rate of Ge-Sb-Te phase-change material.

In this paper, we discuss acousto-optical scanning and deflection, and design an acousto-optical actuator for steering the laser beam in the direction of vertical and horizon. In this system a laser whose wavelength is 532 nm is used and is expanded by a cylindrical lens. This horizontal actuator produces the horizontal deflection and the spherical lens following the horizontal actuator rotates the beam to match the aperture of the vertical actuator. The cylindrical lens restores the beam to its original circular cross-section, after which the microscope optics brings it to a focus in the lithium niobate crystal in which we store information.

According to the multiplicity and redundancy of the record of holography, a new method is presented. Single reference light and separable double object light or overlapped double multichannel holography of space and angle can be realized. The surface image holography supplied in this paper has simple light path, easy operation, clear reproduced image and good result of diffraction. If the noise is eliminated, the it can be generalized from double channel to multichannel, therefore the amount of information can be improved. It is a new way for the making of mould plate of moulded holography image and has a wide application prospect.

Doping CuO, Ce₂O₃ and In₂O₃ in LiNbO₃, In:Ce:Cu:LiNbO₃ crystals have been grown by the Czochralski method. The infrared spectra were measured and the mechanism of the violet shift of OH⁻ absorption peak was investigated. In In:Ce:Cu:LiNbO₃ crystal, Cu and Ce locate at the deep level and the shallow level, respectively. The two-photon holographic storage was realized in In:Ce:Cu:LiNbO₃ crystal by using He-Ne laser as the recording light and ultraviolet light as the gating light. The recording time of In:Ce:Cu:LiNbO₃ is 30 min, which is 10 min shorter than that of Ce:Cu:LiNbO₃.

Doping MnO in LiNbO₃ crystal, Mn:LiNbO₃ crystals of different ratio of Li/Nb = 0.94, 1.00, 1.20, 1.44 have been grown. The crystal of Li/Nb = 1.44 is near chemical metric ratio Mn:LiNbO₃ crystal. Absorption spectra of Mn:LiNbO₃ crystal were measured. Its original absorption edge shifted to red compared with LiNbO₃ crystal. The original edges of Mn:LiNbO₃ crystals of ratio Li/Nb = 1.00, 1.20, 1.44 shifted to violet compared with Mn:LiNbO₃ crystal of ratio Li/Nb = 0.94. When the ratio of Li/Nb increased, the exponential gain coefficient increased and the response time decreased. The exponential gain coefficient (formula available in paper).

Doping CuO, Ce₂O₃ and ZnO in LiNbO₃, Zn:Ce:Cu:LiNbO₃ crystals are grown by the Czochralski method. The optical properties of the crystals are investigated, including photorefractive properties and spectrum properties. The photo scattering resistance ability of the crystal is one order of magnitude higher than that of Ce:Cu:LiNbO₃ and the writing time of the crystal is as half time short as that of Ce:Cu:LiNbO₃. The absorption spectra and infrared spectra of Zn:Ce:Cu:LiNbO₃ were measured. The mechanism of the photo scattering resistance ability of Zn:Ce:Cu:LiNbO₃ was investigated.

Mg:Fe:LiNbO₃, Ce:Fe:LiNbO₃ and Fe:LiNbO₃ crystals were grown by the Czochralski method. The absorption spectra of these crystals were measured. It is shown in the results that the absorption edge of Mg:Fe:LiNbO₃ shifts to violet while that of Ce:Fe:LiNbO₃ shifts to red in comparison with that of Fe:LiNbO₃. In the measurement of the photo scattering resistance ability of Fe:LiNbO₃ and Mg:Fe:LiNbO₃, it is found that the photo scattering resistance ability of Mg:Fe:LiNbO₃ is two orders of magnitude higher than that of Fe:LiNbO₃. The four wave mixing properties, such as the phase conjugate reflectivity and the response time, of the crystals were obtained. Among the three crystals, Ce:Fe:LiNbO₃ has the largest phase conjugate reflectivity, and Mg:Fe:LiNbO₃ has the shortest response time. Using Mg:Fe:LiNbO₃ crystal as the storage material and Ce:Fe:LiNbO₃ as phase conjugate reflector, the associative storage was realized.

Two asymmetric photochromic diarylethenes with different spectra in open and closed form were synthesized simultaneously. Irradiation of the open form with UV light results in essentially quantitative photocyclization to the deeply colored form. The compounds show attractive optical properties and are expected to be used in optical storage and photoswitch.

Doping Pr₆O₁₁ and Fe₂O₃ in LiNbO₃, Pr:Fe:LiNbO₃ and Pr:LiNbO₃ have been grown by the Czochralski method. The lattice constants of the crystals were measured by the x-ray diffraction spectra. The absorption spectra of the crystals show that the absorption edge of Pr:LiNbO₃ and Pr:Fe:LiNbO₃ shifts to red in comparison with that of LiNbO₃,and that of Pr:Fe:LiNbO₃ has the most shifting level, which indicates that Pr:Fe:LiNbO₃ has the high sensitivity. The diffraction efficiency of Pr:Fe:LiNbO₃ was obtained as high as 63% by the two-wave coupling light path.

Lithium niobate crystals doped with the photorefractive sensitizing impurities of MnO and/or CuO have been grown by the Czochralski method. The crystals were treated with the oxidation or reduction. The absorption spectra of LiNbO₃, Mn:LiNbO₃, Cu:LiNbO₃ and Mn:Cu:LiNbO₃ were measured. For these four crystals, the absorption edge of pure LiNbO₃ is at the shortest wavelength, and that of Mn:Cu:LiNbO₃ is located at the longest wavelength. The exponential gain coefficient, diffraction efficiency, response time and phase conjugate reflectivity were measured. Mn:Cu:LiNbO₃ has the excellent photorefractive properties and holographic storage properties.

The Zn:Fe:LiNbO₃ crystals with vary concentration of ZnO and Fe₂O₃ in the melt were grown by Czochralski technique. The polarization conduction is change to improve the holographic storage properties of the Zn:Fe:LiNbO₃ crystal. The optical damage resistance of Zn:Fe:LiNbO₃ is two orders magnitude higher than that of Fe:LiNbO₃ crystal. Its response time is several seconds. The picture stored in Zn:Fe:LiNbO₃ crystal is clear and it has low noise. The experiment result shows the Zn:Fe:LiNbO₃ crystal is perfect holographic storage material.

In our conduction traditional polarization technology, it is difficult to make the doping ions distribute uniformly. The alternative polarization technique is used to make the Fe³⁺ and Fe²⁺ distribute uniformly in the doped LiNbO₃ crystals by controlling polarization temperature, polarization time and polarization current. The properties of the crystals are improved greatly.

The Tb:Fe:LiNbO₃ and LiNbO₃ crystals with vary Li/Nb ratio in the melt were grown by the top-seed solution growth (TSSG) method and Czochralski technique, respectively. Their Li/Nb ratios were calculated by the lattice parameters. The defect structure of the Tb:Fe:LiNbO₃ and LiNbO₃ with vary Li/Nb ratio in the melt crystals was studied by X-ray analyses and UV spectra. The results show that an increase of Li/Nb ratio in the melts leads to a decrease of the lattice constants, which is accompanied by an improvement of the LiNbO₃ lattice structure because of diminishing concentration of intrinsic nonstoichiometric defects.

Nondoped and Ce₂O₃ doped near stoichiometric LiNbO₃ (Ce:LiNbO₃) single crystals were grown by the top-seeded solution method. The solution with [Li]/[Nb] ratio of 1 contained K₂O component of 10.6 mol%(7.0 wt%). The ultraviolet-visible absoprtion spectra of the crystals were measured in order to analyze their structure. The photorefractive properties of stoichiometric LiNbO₃ crystals were investigated and compared with congruent LiNbO₃ crystal. Two-wave-coupling experiments shown that doped stoichiometric LiNbO₃ crystals exhibited much larger photorefractive gain and faster response speed than congruent ones.

1,2-bis(2-methyl-5-(2-(1,3-dioxolane))-thien-3-yl)perfluorocyclopentene (1a) and 1,2-bis(2-methyl-5- 4-N,N-dimethyl-phenyl)-thien-3-yl)perfluorocyclopentene (2a) were synthesized and rewritable photo-mode muti-wavelength optical recording by the use of them was performed successfully. In amorphous film photochromic media, two laser beams of 532 nm and 650 nm were used in recording and readout simultaneously, and signals with high S/N ratio were detected. The results show that the reflectivity difference between the recorded dot and unrecorded region is greater than 50%, and above all, there is no crosstalk existing in the two diarylethenes, which it is very important to implement successfully multi-wavelength optical recording. The photochromic properties of them were also discussed.

Mechanism of Sb-SR (Sb-type super-resoluiton near-field structure) was studied. Experimental results show that the super-resolution performance of amorphous Sb-SR is considerably better than crystal Sb-SR. Considering that Sb is a semi-conductor with small energy gap, a three-order nonlinear response of surface plasmons is deduced to explain the performance of amorphous Sb-SR. Estimation is made and the calculated results are in agreement with the experimental results. Under the new approach, other semiconductors with small energy gap may possibly possess super-resolution performance.

A diarylethene derivative with thermally irreversible photochromic reactivity and good fatigue resistance has been synthesized. The two-photon-induced fluorescence of the compound is observed by excited with 800 nm beam. The intensity of the fluorescence is found to be proportional to I^1.748, where I is the incident laser intensity, and decays with the increase of irradiation time. The results show that two-photon induced nonlinear photochromic reaction was partially realized. It demonstrates that the compound is a promising candidate for two-photon 3D optical data storage.

In this report, recent experimental results on photopolymer, holographic recording material provided by Technical Institute of Physics and Chemistry Chinese Academy of Sciences, were presented. High-diffraction-efficiency unslanted gratings were made. The recording characteristics of the material are discussed in detail in terms of sensitivity, diffraction efficiency, Bragg angle, dynamical range (Δ n). Variation of diffraction efficiency with different incident intensity are discussed. Finally, one data page in the form of 256*256 pixel array has been stored and retrieved with low bit-error rate in this photopolymer media.

The optical constants of each layer in the optical disk are assumed to be constant regardless of film thickness in conventional optical design and optimization of the multilayer structures. However, this assumption is not valid when the layer becomes very thin for its discontinuity. As we know, very thin layers (< 50 nm) are included in the high-density and super-high density optical disks, such as DVD-RAM, high-density DVD (HD-DVD), and super-resolution near-field structure (Super-RENS). In this paper, the thickness error sensitivity factor for dielectric optical multilayer was derived from the optical matrix, and the change of optical constant of the very thin layers with the film thickness variation is analyzed at the same time. The effect of the thickness error and corresponding refractive index change on the reflectivity or reflectivity contrast of the optical disk multilayer was analyzed with a numerical calculation. As an example, we made a structure optimization for the 4-layer DVD-RAM systems with GeSbTe and AgInSbTe phase-change materials as recording media. These results are significant in improving the accuracy of optical design and thermal simlation of high density and super-high density optical disks.

The aberrations are introduced by a hemisphere solid immersion lens (SIL) with a thickness error or a lateral eccentricity in the SIL optical data-storage system. Numerical computation about these aberrations is presented. We have investigated the influence of these aberrations on the focus spot size, signal intensity, and signal contrast. The simulation results show that a tolerance of the SIL is about ± 20μm in the thickness or in lateral eccentricity.

The problem of non-destructive readout prevents the diarylethene from application in practice. In this paper, we selected the gel electrolytes basd on PMMA as the materials of film and successfully achieve the almost same phenomenon of that compound 1 reacts in the solution including supported electrolytes. (See the figure below.) This provides a good support for the practice application of diarylethene.

A layered superlattice, WO₃-polymer/1,10-decanediamine (1,10-DAD) self-assembled multilayer film, has been fabricated by means of alternating adsorption of transition metal tungsten compound and 1,10-DAD. UV-visible spectra were employed to study the growth process. The well ordered superlattice multilayer structure of WO₃-polymer/1,10-DAD SAM film was identified by small angle X-ray diffraction (SAXRD) study. The d space of the SAM film was calculated as 2.897 nm from the SAXRD data, which agrees well with the results get by thickness measurement. The SAM film showed better photochromic properties compared with those of pre-reported WO₃/4,4′-Bis(aminomethyl)-Biphenyl (4,4′-BAMBP) system. It's found that the exciting improved photochromic properties of WO₃-polymer/1,10-DAD films come from the polymerization of WO₃ molecules in the inorganic layers. The results clearly show that the organic molecules can efficiently manipulate the microstructure of the inorganic layer as well as the photochromic properties of the self-assembled multilayer films.

With the development of computer network, information sharing is becoming the necessity in human life. The rapid development of CD-ROM and CD-ROM driver techniques makes it possible to issue large database online. After comparing many designs of dummy CD mirror database, which are the embodiment of a main product in CD-ROM database now and in near future, we proposed and realized a new PC based scheme. Our system has the following merits, such as, supporting all kinds of CD format; supporting many network protocol; the independence of mirror network server and the main server; low price, super large capacity, without the need of any special hardware. Preliminarily experiments have verified the validity of the proposed scheme. Encouraged by the promising application future, we are now preparing to put it into market. This paper discusses the design and implement of the CD-ROM server detailedly.

In order to protect important content, such as the latest Hollywood movies, a new method of anti-piracy technology -- Embedded copy protection ASIC controlling scheme has been developed. The contents on the disk have been scrambled. Before the content playing, the VCD/DVD Player with embedded copy protection ASIC will detect the disk and need user inputs a license code. If the code matches the embedded ASIC key scheme, the disk will play, or the disk will be rejected.

Doping CuO in KNSBN crystal, Cu:KNSBN crystal was grown by Czochralski technique. The exponential gain coefficient, response time, self-pumped phase conjugate reflectivity and phase conjugate response time of the crystal were measured. The exponential gain coefficient of Cu:KNSBN crystal achieved 24 cm⁻¹ and the response time was 1.2s. Self-pumped phase conjugate reflectivity could reach 65% and phase conjugate response time was between 3 to 5s. The inhabitation of Cu ions in KNSBN crystal was primarily investigated.

In this paper, the optical properties induced by laser irradiation in managanese phthalocyanine [Mn(OH)Pc] thin film were investigated with the Ar⁺ laser (514.5 nm) irradiation. The reversible changes of spectra in the region of 630 - 750 nm were observed. The refractive index and extinction coefficient before and after laser irradiation were determined. The results imply that the changes of the film optical properties are induced by photo-thermal processes, and this characteristic is significant to phthalocyanine film as promising candidate for DVD-rewritable recording medium (DVD-RW).

With the increasing demand of huge volume, high density and high transmission speed in optical storage, researches on multi-layer storage and multi-wavelength, multi-layer and multi-level storage in a single substrate have started both in China and abroad. This requests new feathers in optical system of optical disks. The objective lens in multi-layer storage needs compensations to varied spherical aberrations produced by varied thickness of storage layers; the objective lens in multi-wavelength and multi-layer storage needs apochromatism to broadband range. If the apochromatism is not ideal, it is needed that the spherical aberrations of multi-wavelength light are uniform and the multi-wavelength light beams are focused separately to obtain better result. A traditional micro-objective whose optical aberration is carefully corrected can be apochromatic to D, F and C in medium numerical aperture and can be used as objective lens of the optical disk of multi-wavelength, multi-layer and multi-level optical storage. This article gives an amended result based on C. G. Wyne's field flattener. The calculation result of optical aberration indicates that the spherical aberration is nearly zero and the secondary spectrum is less than 0.5 times of focal depth. It is also indicated that the MTF of a certain wavelength light matches the ideal MTF curve wherever on axis or off axis, wherever on meridian surface or on sagittal surface.

In order to meet the development requirements of high density, high capacity and high integration in the field of optical storage, a new scheme for optical recording system is supplied in this paper. At the same time the methods about disc alignment, position and clamping are discussed in details. The principle of flexure hinge is adopted. The results of experiments show that the scheme is feasible, and the setups for optical discs can meet the requirements.

Basing on the structure of multi-layer parallel-accessed disc, current modulation code is optimized to achieve higher density storage. Two problems, which may be serious after the optimization, are discussed: acceptable jitter and synchronization process of PLL. A novel method for procuring combined signal of channel bit clock for multi-layer disc is proposed, which satisfies the requirements of PLL. The novel method is at last proved by probabilistic theory. At the end of this paper, parameters of RLL for multi-layer disc are presented: d=4, k=10~15. These new parameters improve the track-density by 15% ~ 20%.

In this paper, modified finite differential time domain (FDTD) method is used to investigate super resolution near-field structure (Super-RENS). The random distributed Ag particles, which is responsible for the localization and the enhancement of the surface plasmon within the Super-RENS, is included in this simulation. The near-field optical distribution when recording mark is just beneath the nonlinear aperture is achieved. And the transmitted readout signal is also simulated.

Co-doping photo-refractive sensitive dopants CeO₂, CuO and Fe₂O₃, Ce:Cu:Fe:LiNbO₃ crystals were grown by Czochralski technique for the first time. The absorption spectra of the crystals were measured. The absorption edges of Cu:LiNbO₃, Fe:LiNbO₃ and Ce:Cu:Fe:LiNbO₃ crystals shifted to red compared with LiNbO₃ crystal and the absorption edge of Ce:Cu:Fe:LiNbO₃ crystal shifted to red compared with Cu:LiNbO₃ and Fe:LiNbO₃ crystals. The exponential gain coefficients of Ce:Cu:Fe:LiNbO₃ crystals with different thickness (0.2 mm, 0.4 mm, 1.0 mm and 2.0 mm) were measured. The exponential gain coefficient of thin crystal sample increased. The mechanism of the enhancement of the exponential gain coefficient of thin crystal was investigated.

Doping CeO₂ and Tb₄O₇ in KNSBN, the Ce:KNSBN crystal was grown. It is the first time that the crystal was grown by Czochalski. The phase conjugate reflectivity was measured to be the higher than 140% on transient state and to be higher than 90% on stable state. The out electric field can enhance the phase conjugate reflectivity on transient state. When E_O equals 4 kv/cm², the transient phase conjugate reflectivity R equals 168% and the stable transient phase conjugate reflectivity R equals 120%. Ce:Tb:KNSBN crystals pumping on self phase conjugate reflectivity goes up to 62%. Cu:KMSBN was used as recorder and Ce:Tb:KNSBN was used as self-pumped conjugate to realize holographic associative memory.

Pr:LiNbO₃ crystal can be used in two-color gated storage process for its special energy-level structure. Compared with other crystals used as volume holographic storage media, it has a great merit that an image recording does not erase the recorded one in multiplex storage process. But its photorefractive effect appears weaker than other crystals in the same conditions. We doped photorefractive sensitizing element Ce into Pr:LibNO₃ to get Ce:Pr:LiNbO₃ crystal with Czochralski method. The structure of crystals has been determined by X-ray powder diffraction method. The results indicate Pr:LiNbO₃ and Ce:Pr:LiNbO₃ keep the same structural characteristics as pure lithium niobate. In the absorption spectra of Pr:LiNbO₃ and Ce:Pr:LiNbO₃ samples with non-polarized light in wavelength of 300 - 900 nm, the absorption edge of Ce:Pr:LiNbO₃ shifts to the red compared with that of Pr:LiNbO₃. The diffraction efficiency, writing time and especially erasing time of Ce:Pr:LiNbO₃ have been measured. We find that maximum diffraction efficiency of Ce:Pr:LiNbO₃ has increased without at cost of decreasing the erasing time. The effect of doping ions on the optical properties of Ce:Pr:LiNbO₃ crystal as holographic recording media has been studied systematically.

The congruent tri-doped Mg:Mn:Fe:LiNbO₃ crystals have been grown by Czochralski method in air atmosphere. The crystal samples are reduced in Li₂CO₃ powder at 500°C for 24 hours or oxidized for 10 hours at 1100°C in Nb₂O₅ powder. Compared with as-grown Mg:Mn:Fe:LiNbO₃, the absorption edge in UV-Vis. absorption spectrum of the oxidized sample or the reduced shifts to the red. The post-disposal, oxidation or reduction disposing has no effect on O-H vibration absorption peak in infrared region. In two coupling experiments we determine the writing time, maximum diffraction efficiency and the erasure time of crystal samples in the same conditions. The results indicate that oxidation and reduction disposing has great effect on the holographic recording properties of these crystals. The reduced crystal exhibits the fastest response time 145s and the biggest diffraction efficiency 67% among the crystal series. The mechanism of post-disposing effect on the holographic recording properties of Mg:Mn:Fe:LiNbO₃ crystals has been investigated.

By using Poly(methyl methacrylate) (PMMA) as a host matrix of the materials, we investigate photorefractive property of PMMA-based polymer. The photorefractive index of the materials is experimentally measured by using two-beam coupling method. Because the nonlinear optical molecules, such as phenanthrene quinone (PQ) and azo-dye molecules etc, have been doped with PMMA, the results show that the photorefractive effects are improved evidently. Furthermore we find that the influence of outside electric field on photorefractive property of PMMA-PQ polymer are evidently decreased. The glass transition temperatures of the polymer and the doping amount of chromophore in PMMA are also discussed. Some good results have been obtained.

A solid immersion lens (SIL) using in high-density optical recording works by changing evanescent waves (in the condition of high N.A.) into propagating waves through tunneling effect, and the rays are focused on recording medium. So the transmissivity and the tunnel width is a sharp conflict. The analysis and brief calculation in this paper show that, the transmissivity angular spectrum of hemisphere SIL(HSIL) and super hemisphere SIL(SSIL) is obviously different. When the tunnel width is narrow (about 1/10 λ), the former (HSIL) has a high transmissivity than the latter (SSIL) only when the N.A. is near the highest. But if the width becomes larger, the transmissivity of SSIL is always better than that of HSIL. And when the width is about 1/2 λ, the high-N.A. transmissivity of both is nearly zero.

Ce:Cu:KLN crystals were grown for the first time. The lattice constants of Ce:Cu:KLN crystals were measured and calculated. The Ce-ion and Cu-ion sites in the crystal were made certain. The gain coefficient and response time were measured. The exponential gain coefficient of Ce:Cu:KLN crystal is 8.0 cm⁻¹, response time is 1.4s. Erase time of Ce:Cu:KLN crystal was measured. Along with the enhance of the intensity of the reference light, the erase time declines.

In this paper, a novel double encryption technology is presented. It can encrypt data with not only double phase codes, but also the wavelength. The phase keys and the wavelength keys must be known simultaneously to retrieve the encrypting data, otherwise, the reconstructed data will be white noise like. The basic configuration and principle of optical holographic storage system are first introduced. Holographic data storage can be encrypted by coding the phase of reference beams through orthogonal phase coding. Double phase-encoded holographic storage can be done by placing two phase masks on the input plane and FP plane respectively. When one wants to retrieve the data, he must have the same mask placed on the FP plane, otherwise the data can not be reconstructed. Finally, the encrypted holographic storage system combining optical wavelength and double phase codes is presented theoretically, and proved to be valid by the computer simulation.

In this paper, the diffractive efficiency in Ce:SBN photorefractive crystal was measured using two-wave coupling light path. The light-induced scattering resistance was gained through observing the transmitted light spot. Furthermore the other holographic storage properties such as the quality of the stored image and preservation time were studied. Finally using Ce:SBN photorefractive crystal as the storage medium, storing and reconstructing the holographic image were realized.

A diffractive superresolution element placed at the exit pupil can effectively increase the resolving power of an optical system for optical data storage. The theory of linear programming is suggested in this paper to design the diffractive superresolution elements, which can get globally optimal solutions. Examples of design and some limits of optical superresolution are presented, and a comparison between the results for a uniform incident field and those for a Gaussian incident field is performed.

A new technique with a one-step rainbow hologram for recording 2-dimension or 3-dimension images is presented. In this method, not only can we realize to record rainbow hologram in the same recording material with multiplex angles, but also obtain laminated result. The hologram has a low speckle noise and a high diffraction efficiency when it reconstructed with white light.

In a Local Area Network (LAN), clients are permitted to access the files on high-density optical disks via a network server. But the quality of read service offered by the conventional server is not satisfied because of the multiple functions on the server and the overmuch caller. This paper develops a Linux-based Network-Attached Storage (NAS) server. The Operation System (OS), composed of an optimized kernel and a miniaturized file system, is stored in a flash memory. After initialization, the NAS device is connected into the LAN. The administrator and users could configure the access the server through the web page respectively. In order to enhance the quality of access, the management of buffer cache in file system is optimized. Some benchmark programs are peformed to evaluate the I/O performance of the NAS device. Since data recorded in optical disks are usually for reading accesses, our attention is focused on the reading throughput of the device. The experimental results indicate that the I/O performance of our NAS device is excellent.

Doping ZnO with the concentration of 3mol% and 7mol% in Ce:Mn:LiNbO₃, respectively, Zn:Ce:Mn:LiNbO₃ crystals were grown by Czochralski method. The optical damage resistance ability of crystals was measured. The optical damage resistance ability of Zn (7mol%):Ce:Mn:LiNbO₃ crystal is two orders magnitude higher than that of Ce:Mn:LiNbO₃ crystal. The exponentional gain coefficient, diffraction efficiency, response time and effective charge concentration were also obtained. The response speed of Zn(3mol%):Ce:Mn:LiNbO₃ and Zn(7mol%):Ce:Mn:LiNbO₃ crystal is two times and four times higher than that of Ce:Mn:LiNbO₃, respectively. The mechanism of optical damage resistance ability of Zn:Ce:Mn:LiNbO₃ crystal was researched.

We have delivered an idea, based on multiple level coding, to read and write with the multiple level tracking system. By utilizing off-track recording and multi-level coding, we may increase the track density to expand the optical disc density. Off-track recording is a design using LC diffractive optical element (LCDOE) to control the recording beam in desired angle. Another beam is for reading and tracking.

The research of high density optical storage system leads to the high density of tracks and pits of the disc. The track pitch of high density optical storage system is much more narrow than that of ordinary optical disc such as DVD. The first step in the production process of both pre-record data and recordable optical discs is mastering. Thus in the high density optical storage system the stable and accurate mastering performance is of greatest importance. This paper presents a control scheme that provides fast, accurate and stable mastering performance. Because of the high density of the track on the optical disc, the conventional control of mastering scheme is unfit for good mastering performance. In this paper we review the development of optical storage system and analyze the problems that may arise when the conventional control scheme is applied to the high density optical disc mastering system. In the proposed scheme, a new tentative control system is designed. The performance of the proposed tentative control scheme is shown by experiments in the high density optical disc mastering system.