3D optical data storage can benefit from the non-linear process of two-photon absorption (TPA). If some chromphores with large TPA cross section are introduced into the diarylethene to enhance its two-photon absorptivities, it is expected to be good recording media for 3D optical data storage. The authors have synthesized four diarylperfluorocyclopentene (DPFCP) derivates for the purpose of developing two-photon 3D optical data storage. The nonlinear two-photon absorption (TPA) properties of the compounds were examined, and the reaction and excited state relaxation dynamics after two-photon excitation were investigated. The TPA cross sections of 2-position DPFCPs were measured by means of TPIF (two-photon induced fluorescence) method, and the highest is 48×10^-50cm⁴•s•photo^-1•molecule^-1. The compounds were successfully applied in two-photon 3D optical data storage based on single beam two-photon femtosecond writing and one-photon fluorescence reading. Ten-layer clear images on DPFCP/PMMA film were obtained, and the data storage density is high to 2.0×10¹¹ bits/cm³.

Based on DWDM technology, optical fiber head can be used to realize multi-wavelengths parallel transmission. An integrated optical fiber head has been optimum designed, which can be used in the multi-layers storage system. The pick-up signal intensity distributions have been simulated for the multi-layers parallel storage system.

Multi-wavelength and multilevel (MWML) optical storage with photochromic media is a novel technology that can increase storage capacity and transfer rates significantly. Signal processing and coding methods for the MWML storage channel are introduced in this paper. Two-dimensional codes with parallel detection and equalization are studied to increase storage capacity and combat the crosstalk between different wavelength materials. Multilevel amplitude modulation and M-ary runlength-limited (RLL) codes are described and compared for achieving higher coding capacity. The novel MWML recording technology has the potential to be applicable for the next generation optical data storage.

In order to meet the requirement of focusing in the multi-wavelength mastering system, a pneumatic sensing system is designed. It detects the objective lens position signals and sends to the focus control system as the focus error signals instead of the feedback signals of light intensity used traditionally. So it can solve the auto-focus problem caused by introducing multi-wavelength lasers. The static and frequency response characteristics of the system are tested. It is proved by the experiment that the focus error is under ±0.1μm and can meet the needs of the three-wavelength system.

Multi-wavelength storage is an approach to increase the memory density with the problem of crosstalk to be deal with. We apply Low Density Parity Check (LDPC) codes as error-correcting codes in photochromic dual-wavelength optical storage based on the investigation of LDPC codes in optical data storage. A proper method is applied to reduce the crosstalk and simulation results show that this operation is useful to improve Bit Error Rate (BER) performance. At the same time we can conclude that LDPC codes outperform RS codes in crosstalk channel.

This paper presents the system design of double-layer Blu-ray Disc recorders built in Philips Research Laboratory. The system architecture, new components, and the advanced signal processing are addressed. The experimental results show that writing HDTV programs to double-layer Blu-ray Discs and reading them back have been achieved. In addition, this paper demonstrates that discs with higher density and higher capacity are possible with the advanced technologies developed.

Near-field optical recording based on solid immersion lens (SIL) system has attracted much attention in the high-density storage in recent years. The recording spot size can be decreased using the SIL effectively. 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 experimental result with recording spot size 200 nm is presented. The influence factors in SIL near-field recording system are also discussed in the paper. Near-field optical virtual probe (NFOVP) is a kind of virtual probe by the evanescence wave interference and aperture diffraction based on SIL. It has a great potential in near-field optical data storage. In this paper, the most important characteristics of the NFOVP has been revealed through numerical simulation. The FWHM of central peak, the size of near-field virtual probe is constant whatever the distance increases in a certain range so that the critical nano-separation control in the SIL near-field data storage system can be relaxed. A realization model of NFOVP based on SIL system for data storage has been proposed and the simulation result based on this model is presented.

To achieve 50nm flying height and accuracy tracking motion, it is essential to reduce the whole size of optical flying head (OFH) to improve mechanical and optical performance. With a view to the practical applicability, a novel integrated OFH based on the combination of SIL and objective lens (OL) is proposed, which possesses both high optical performance and reasonable tolerance in assembly. In addition, the fabrication process of this OFH is illustrated in detail. Finally, the main parameters of ABS for OFH slider are presented by means of numerical simulation. The simulation result demonstrates that the flying height of the integrated OFH slider can keep stable from 43nm to 44nm at different radium of optical disk, which can yield high signal/noise ratio optical signal during the read/write motion in near field recording (NFR) system.

The super-resolution near-field structure (super-RENS) is an ultrahigh-density near-field optical disk data storage medium which can achieve superior spatial resolution. Our previous studies found that enhanced local optical intensity occurred at the near field of the super-RENS disk, and the nonlinear near-field optical enhancement is related to the localized surface plasmons of silver clusters dissociated from the AgO_x layer of the super-RENS disk. In this paper, we report the near-field and far-field properties of AgO_x-type super-RENS with different embedded silver nanoparticles using two-dimensional finite-difference time-domain (FDTD) calculations. Highly localized enhancements are found between adjacent silver nanoparticles in the near fields. The far-field signals of different types silver nano scatters confirm the super-resolution capability of AgO_x-type Super-RENS disks. The behaviors of far-field signals indicate the correlation between the enhanced localized surface plasmons and the super-resolution capabilities of AgO_x-type super-RENS.

Multi-layer recording method has been studied and developed since dual layer disk of DVD-ROM and the studied disk type has expanded from ROM to Rewritable disk. Multi-layer disk has new problems different from a single layer disk. One is an inter-layer cross-talk, which a component of a signal from adjacent layer leaks into a detected signal when the information data is reproduced from a target layer. Second is a recording power fluctuation, which the light power reached a target layer changes by marks on intermediate layers. There were many works that solve this problem. This causes severe problem for signal processing and recording performance. There was work that was proposed to design the structure of a multi-layer disk and an optical head. In this paper, we reported the consideration of a code in order to solve the problems.

Rotational speed of optical drives and servo speed of optical pick-up actuators should be higher to meet high performance for optical drives. One of the methods to achieve such a high performance product is to increase an input power for the coil, but a heat problem generated by the coil will become serious. Two kinds of new ferrofluids have been designed to transfer a heat from the coil of optical pick-up actuator. Their physical properties have been properly designed to be functioned at a wide operating temp. and various aspects of their reliability including resistance for deterioration to high temp. and humidity, etc., have been evaluated. Also, they have been applied to optical pick-up actuators and the properties of ferrofluids such as heat transfer and shock resistance have been examined. The life tests showed that the new ferrofluids had at least two times longer life and a smaller viscosity change than CF-3A, which has been used in commercially available optical pick-up actuators. The new ferrofluids could tolerate the shock of 500 G without a ferrofluid splash, the coil temp. with the ferrofluid was about 10 degrees C or more lower than the one without it at the same input power.

The radial tilt between vertical direction of disc and optical axis of lens in standard DVD traverse, plane vibration and warp of disc are important parameters in production and detection of DVD discs. In this paper, a new dynamic detection method which we call pulse-width method is proposed to detect the radial tilt, plane vibration and warp through analyzing the optical and electrical features of traverse. Based on the method, an apparatus is developed and the experimental results compared with the analysis results verify the validity of the method. The applicability and testing precision are also analyzed.

After analyzing the system architecture and the routine design method of a SCSI controller, one novel design project for the SCSI controller is proposed on the basis of SOPC and soft processor IP core technology. The NIOS soft processor IP core is chosen as the center controller in the application system. Except for NIOS processor, most of the peripherals around the SCSI module, including DMA data channel and data cache control logic, are integrated into one FPGA chip. Comparing with the routine design method, the new project has better features in the expansibility, scalability, improvability and in-system programmability. As an instance, the SCSI to ATA interface system based on SOPC is introduced and given the satisfying I/O speed test results.

Storage technology has enjoyed considerable growth since the first disk drive was introduced nearly 50 years ago. Various storage devices with large volume and high performance are emerging and they carry the important information for our social life. How to make the devices more broadly and effectively used and make the information more available is a problem for today. IP-based Storage provides such a cheap interface for storage devices under the rapid development of network technology. This paper answers what is network storage relative to traditional storage and then puts emphasis on two typical IP-based storage technologies NAS and iSCSI. The article evaluates the performance of NAS and iSCSI by measuring and analyzing file-level access performance and block-level access performance. Our test results show that iSCSI provides higher performance then using NFS protocol in Linux or SMB protocol in Windows (NAS scheme). The last part of the paper gives characteristic and trade-off of several IP-based storage system architectures.

A practical mastering technology was developed using a blue laser optical mastering system with a wavelength of 405 nm, a numeric aperture (NA) of 0.95 and a phase-shift apodizer. The laser is shaped and collimated by a space filter with its diameter 2μm, then is split into two beams by polarizing prism. One beam is used to detection of the optical power, and the other beam is used to write data on the disc. The phase-shift mask is lay between the collimating lens and the polarizing prism to optimizing the intensity distribution of Airy point on the disc. The lens with high NA 0.95 is designed to make the image point of the laser less then the diffraction point. The air-operated focus control device is used to focalize the light on the disc. Based on the technology, the recording spot with its diameter about 223nm is achieved.

The non-linearity of the super-RENS mask can be used in optical data storage, which can greatly increase the disk’s density. Experiment is carried on the traditional mastering system with modification. We adopt the SiN/Sb/SiN multiplayer as the mask to insert the optical mask. For 413nm semiconductor laser and lens with NA=0.9, the diffraction limit is 200nm theoretically. Mark-120nm much smaller than that size is generated in the experiment. The thickness of Sb in the mask layers has much effect on the mastering signal intensity. For different power, we should control the thickness of Sb film. The experiments results show that the super-RENS mask can actually reduce the size of the mark obviously and realize the high density optical storage.

Two stage positioning method which is composed of coarse positioning and fine positioning is a way to increase the precision of linear feeding in high density disk mastering. The control method of two stage positioning is proposed in this paper. Different control models are compared and the suitable one is chosen. The PID controllers for coarse and fine tables are designed. The numerical simulating results show that the two stage positioning system with PID controllers has good performance in linear feeding with steady error less than 10nm. The coarse positioning table compensates the major component of displacement in linear feeding while the fine positioning table compensates the minor one. The two stage positioning system can well satisfied the requirement of high density disk mastering in theoretical.

An effective application of band-limited diffuser is introduced to realize the dual-wavelength method which can reduce the grating decay while retrieving data in the volume holographic data storage. The Diffuser combined with the imaging system can generate enough wavefronts to match the Bragg conditions of all the pixels in the whole image when two wavelengths are used. It is possible to enlarge the size of the retrieved image and get an approximately uniform diffraction efficiency. Experimental setup is presented and the results show that this technique is effective.

The recent research on high-density, large-capacity, nonvolatile holographic storage in photorefractive crystals, carried out at Beijing University of Technology, is reviewed in this paper. A batch thermal fixing technique was developed to overcome the volatility of a large number of multiplexed holograms, which has also proved to increase the effective dynamic range of crystals, hence to increase the storage density. The key of this technique is determination of the inter-batch optical erasure time constant that is much longer than the convenient (intra-batch) erasure time constant of the crystal. Disk-type storage is proposed to increase the degree of spatial multiplexing, so that the whole volume of the material can be used for storage, and the capacity increases remarkably. Incorporating batch thermal fixing into holographic disk storage yields to a track-division thermal fixing (TDTF) scheme for holographic disk storage to overcome the volatility of information and increase the storage density and capacity as well. Analyses and experimental results on a high density of 50 bits/μm² (10 Gbits/cm³) show that high-density huge-capacity mass storage, indicated by storing 1 tera-bits or more data in a single crystal of reasonable size, can be achieved by means of TDTF holographic disk storage scheme.

Two photochromic fulgides, 3-[2-(N, N-dimethylaniline)-5-methyl-xazolemethylene]-4-isopropylidenetetrahydrofuran-2, 5-dione (A) and 3-(1,2-dimethyl-5-phenyl-pyrrolmethylene)-4-isopropylidenetetrahydrofuran-2, 5-dione (B), doped in PMMA as candidates of dual-wavelength optical memory for parallel recording are demonstrated. With 488nm-laser and 650nm-laser, both “cross” and “star” images are recorded on the same place of the sample and readout. Cross-talk between two fulgide compounds in PMMA matrix is also investigated.

A series of inorganic-organic photochromic ultra-thin films were fabricated by self-assembly. The photochromic properties as well as structure of the prepared ultra-thin films were discussed. It is found that the photochromic properties of the ultra-thin films were closely related to the building blocks of the films. Both the organic and the inorganic components of the self-assembled films can evidently effect the structure and photochromism properties. The optimized combination of the inorganic and organic building blocks is thus provided.

Dopants can be substitutionally incorporated into AgX crystals and influence the photoelectron action and the latent image formation by introducing appropriate electron traps. The dopant [IrCl₆]^4- was introduced in either the core, the subsurface shell or the outer shell of cubic AgCl microcrystals and its concentration was varied from 2.60×10^-7mol/molAg up to 2.61×10^-5mol/molAg. The emulsion sample exposed to a YAG super short pulse laser (355nm, 35ps) were measured by microwave absorption and dielectric-spectrum technique. The experimental results show the photoelectron decay time at room temperature decreases with the doping concentration increasing for any given doping position especially as the doping near the core. Results also show the photoelectron decay time at room temperature increases when the doping position is closer to the surface especially for higher doping concentration at 2.61×10^-5 mol/molAg. This can be explained that [IrCl₆]^4- can act as both shallow electron trap and deep electron trap with doping condition varying. When the doping level is lower and doping position is closer to the surface, the sensitivity of AgCl emulsion is higher. The knowledge obtained from this study may be useful for practical microcrystal design making use of dopants.

Photoelectrons play an important role during the photographic process of silver halide. Electron traps influence the decay of photoelectrons and the photographic process as well. During the preparation of silver halide microcrystal, traps will be formed with different depth, concentration, and capture cross section under different conditions such as temperature, pressure, and nucleation time etc. The electron trap with different depth, concentration and capture cross section has different ability to capture photoelectrons. In this paper, the influences of the three parameters on photoelectron decay are theoretically analyzed from the point of the photoelectron decay kinetics, respectively. It is found that decay amount is determined by capture cross section; decay velocity depends on trap depth; trap concentration influences both decay amount and velocity. Photo-storage or imaging character of silver halide material can be changed and improved by changing the size of capture cross section, depth or concentration under certain condition to control decay amount or velocity.

A practical method of suppressing photovoltaic noise in photorefractive iron doped lithium niobate crystals (Fe:LiNbO₃) is proposed, in which the surfaces of the crystal are coated with transparent electric-conductive material (In₂O₃ doped stannum, ITO) forcing the crystal to operate in a short-circuit mode. In order to assess the validity of this method, the loss of signal-to-noise ratio (LSNR) was used to evaluate the quality of images formed directly through uncoated and ITO- coated crystals respectively. Several iron doped lithium niobate crystals were measured. The main experimental results showed that the scattering noise decreased obviously in the ITO-coated crystals, suggesting that the short-circuit operation suppressed photovoltaic noise effectively. Furthermore, it is found that the dynamic range (M#) of the crystals increased after they were coated with ITO. The results of experiments on multiple hologram recordings in the uncoated and ITO-coated Fe:LiNbO₃ crystal verified the improvement of M# well.

Photopolymer is an optimum material for practical holographic storage because of low cost and good characteristics. A new epoxy resin-photopolymer is reported. Polymeric binder is epoxy resin whose refractive index is high, but the monomer’s refractive index is relatively low. The design can make monomer transfer freely in rigid frame, so we can realize no-shrinking recording and stabilize the recorded hologram. Simple grating is recorded in films, then we obtained the relationship curve between the exposure energy and diffraction efficiency by sending a single beam into the photopolymer film. According to the exposure curve, there is a recording delay, so the pre-exposure is needed to sensitize the material. In order to avoid cross-talk between contiguous holograms, angle selectivity of the material is measured. Then we investigate how diffraction efficiency is distributed in all multiplexed holograms with equal-time exposure. One method of calculating exposure schedule for multiplexing holograms in photopolymer with equal efficiency is presented. By using such exposure schedule, holograms are recorded at a single location by angle multiplexing, and the uniformity of their diffraction efficiency is remarkably improved. After iterating the procedure, it is possible to achieve much more uniform diffraction efficiency.

Although recordable disk are rapidly developing, the mainstream in the market is still the read-only manufactures such as CD-ROM and DVD-ROM which have prerecorded information. How to enhance the storage density of read only memory is one of the hotspots in optical data storage. The authors put forward novel theory for read only memory. The novel theory takes little organic molecule as memory medium of read only memory, and the writing process is photon-mode, which is called organic photonic read only memory (OP-ROM). According to the novel theory, disks can be massively copied by exposure. Furthermore, because of diversity and modifiability of organic molecules, the storage density can be improved by multi-wavelength, multi-level and multi-layer.

Optically-assisted magnetic recording (OAMR) can solve fundamental problems concerning thermal fluctuation and write capability in magnetic recording, and it is regarded as the key technology in achieving density exceeding 1 Tbit/in². OAMR is classified into magnetic dominant recording and optical dominant recording, and differences with respect to the recording method and effect between them are described. Magnetic dominant recording was conducted on longitudinal synthetic ferrimagnetic media to prove the fundamental effectiveness. Both SNR and overwritability without thermal erasure were assured. A theoretical estimation in optical dominant recording suggests that OAMR enables 10 times density compared with conventional magnetic recording. Butted grating should provide good optical characteristics as the heating element for optical dominant recording, and it also has compatibility with the conventional magnetic head for integration.

The paper suggests a new scheme of hybrid recording by high refractive index optical waveguide; analyzes the waveguide exit optical field and the near field optical spot energy distribute of the hybrid recording medium surface. We succeed to use the Maxwell electromagnetism theory to model and simulate the waveguide exit energy distribute, obtained the near field optical spot of the hybrid recording medium surface. According to energy balance way, a new model has been adopted and the hybrid recording medium temperature gradient has been studied. The Thermal modeling of two-dimensional transient temperature distributed by the finite element method is studied; with this tool, the hybrid recording medium temperature gradient has been obtained. The hybrid recording areal density may be decided by the dual-gradient (the thermal gradient and magnetic field gradient). According to the simulated results, the track density can reach 500KPTI, if the bit density is 1000kbPI, the area density will be 500Gb/in².

Combining the advantages of hard-disk magnetic recording and magneto-optical recording, hybrid recording is regarded as promising candidate for extremely-high density recording technology beyond Tera bits/in². To obtain such high areal density, hybrid recording media are required to have high coercivity and large remanent magnetization at room temperature, the desired temperature dependence of coercivity and magnetization, as well as very short thermal response time. Currently, the researches on the hybrid recording media mainly involve the magnetic hard-disk polycrystalline recording media and the magneto-optical amorphous media. This report presents the latest progresses in the researches on these two kinds of media for hybrid recording.

This study examined a lifetime estimation method for optical disks. It is based on the Eyring acceleration model and statistical analysis. The statistical distribution of life data for the optical disk assumed a lognormal distribution. Analysis of statistical techniques based on the ISO standard is proposed as a life expectancy prediction method for CD-R disks. The standardized life expectancy of an optical disk is defined as the minimum lifetime of 95% survival probability at 25/50%RH with a 95% confidence level. An acceleration test was conducted using a high-density optical disk under stress conditions of temperature and relative humidity. Consequently, we confirmed the capability of this method for estimating life expectancy by considering the stresses of temperature and relative humidity, and providing for a confidence level. The statistical distribution function of optical disk lifetime data must be clarified experimentally to apply this technique to lifetime estimation of optical disks in the future.

Higher NA optical pick-ups (OPUs) are being applied in optical storage system for high capacity. As the vector characteristics of the laser beam in high NA OPU play an important role in the interaction between the disc information layer and laser beam, simulations based on both vector diffraction theory and rigorous calculation of Maxell’s equations are becoming more and more important. They not only provide accurate and reliable simulation results, but also make it possible to investigate many other interesting topics e.g. the feasibility of using polarized light to increase storage density of optical discs. In this paper, a software package based on three-dimensional finite-difference time domain algorithm (3D-FDTD) is introduced to simulate readout signals. It can be used to simulate the reflection pattern for three dimension geometrical pits accurately. Moreover, because it can interface with optical design program ZEMAX, the simulation can be done for different light paths and in the presence of surface defects, which is very useful for analyzing and evaluating a practical OPU. The features of this software are expected to help explore new disc formats, understanding signals in servo path and data path, and furthermore designing a new optical pick-up etc.

Following the development of the optical data storage technology, an important issue of reliability should also be paid attention to. The designing core of the reliability test way is simulating the users’ circumstance and the transporting process. The normal simulating is important but the users’ playing situation is extreme irregular. So the normal simulating is not enough for reflecting the virtual operating status. Few long time playing experiments have been done previously. In fact such kind of long time playing experiment is most similar to the users’ playing situation, and the effect is compositive since such playing is influenced by current surges, electrostatic discharges, even dust. It seems simple but it is important. We use the optical pickup heads to make sets to play DVD disc continuously for long time, and monitor the image and effect regularly. In our experiment, the optical pickup heads have operated continuously for 6000 hours. It suggests that such kind of long time playing as an additional reliability testing means is necessary, especially for the DVD player’s manufacturing company.

Vertical degree of pick-up and disc is an important factor that influences reading and writing date in DVD drive. Measuring and adjusting vertical degree of pick-up and disc is a key working procedure in DVD drive manufacture. Now, measuring method in actual production is an indirect measuring, which measure parallel between spindle motor and traverse. It’s not very accuracy as there are error in pick-up assembles. The paper suggests a new method to measure vertical degree of pick-up and disc, new method measure vertical degree of pick-up and disc directly. The key of new method is measure position of laser from pick-up. A specialty optical circuit and fine CCD camera is need. The CCD camera is responsibility for collection information of laser image of pick-up and sends information to a computer. The specialty software responsibility for calculating position of laser and calculating incline angle between pick-up and disc. Because of characteristic of DVD drive manufacture, the algorithm calculating position of laser image must be design for accuracy and quickness. The paper suggests a specialty algorithm to calculating position of laser image. The algorithm is very accuracy and quickly, it can measure 0.05-degree incline angle error. The new method is helpful to automatic adjusting technique vertical degree of pick-up and disc.

This paper principally analyses the influence of the DVD traverse manufacture and assembly error to the servo system, presents a specific servo system applied for DVD traverse tester, which is a digital servo based on general DSP. The repetitive control scheme is adopted to enhance the robustness to the periodic disturbance.

The evaluation and adjustment for characteristic parameters of DVD traverses is the key in the batch production. This paper classifies the parameters and proposes a particular method which possesses the special servo combined with the commercial servo, damping detecting and obliquity detecting, and then constructs an evaluation and adjustment system for parameters of DVD traverses and introduces the economy structure of hardware with module functions and difficulties of software design.

Thermal-fixing holographic storage in photorefractive crystals is an effective nonvolatile storage technique for stabilizing holograms against the optical erasure. The developing characteristics of fixed holograms in iron-doped lithium niobate dominate their final diffraction efficiencies after developing, provided that the ionic compensation in the fixing stage is nearly complete. Developing kinetics of fixed holograms under homogeneous illumination is studied. The effect of developing light intensity on developing efficiency has been demonstrated experimentally. The fixed holograms with the same initial recording grating strength are developed under illumination of the different light intensities, such as 200mW/cm², 400mW/cm², 600mW/cm², and 800mW/cm², respectively. The fixed holograms with the different initial recording grating strengths are developed under illumination of the same light intensities as well. The overdeveloping characteristics of fixed holograms are described. The developing efficiency of the hologram with a given initial recording grating strength is found to depend on the intensity of developing light. These features can be explained with the joint effect of the resulting space-charge holographic field of the fixed hologram and the photovoltaic field under homogeneous illumination.

A calorific equilibrium equation is used to derive the relativities of optimum recording power and pulse waveform parameters in various disc scanning velocities. Based on the model, a new recording parameters calibrating flow is given as a referenced process. A number of optical recording examples have been examined in detail, and the results have been compared with those calculated data by use of a general summation approach.

Three-dimensional optical data storage realized by microexplosion based on a multi-photon absorption process is a promising method to fabricate optical read-only memory with large recording capacity. The writing of multi-layered data bits inside a PMMA block doped with rare-earth ions (Sm³⁺ and Ce³⁺) under multi-photon absorption excited by a 800nm femtosecond (fs) pulsed laser was reported. The fs pulsed laser beam was focused into the sample with a microscope objective (N.A.= 0.65 40X), and bits were recorded as structurally altered regions which have high contrast in refraction index and fluorescence intensity. The recorded bits could be retrieved parallel by transmission using a conventional optical microscope or be read out serially by fluorescence signal of the structurally altered region excited by a 514.5nm laser using a reflect-type confocal microscope. Experimental results of three-dimensional recording and reading with 4-um in-plane bit spacing and 8-um inter-plane spacing in eight layers were presented. The structure changed in the material before and after the laser irradiation was discussed.

In the past few years considerable demand has developed for oceanic data storage system that are able to store Petabytes data. Volume holographic recording has the potential to offer high density, fast data readout rate, and associative content addressable storage as compared with other conventional mass data storage technology. However, its total cost and size impedes to go into market. If the volume holographic device could join network and be shared by more and more customers, the average cost for each customer should be reduced. On the other hand, the growing network storage technologies shake off the traditional storage architecture (DAS) limit including physical topologies and access mode, and provide high scalability, availability and flexible for storage system, moreover are widely applied to many fields. Obviously, it is valuable for building network storage device based on volume holographic. In this paper, we design the architecture and relative software of volume holographic device to enable common storage network, which can support the SAN based on Fibre channel and iSCSI. Our experiment shows the HSD (Holographic Storage Device) has excellent performance for network storage.

The readout of photochromic multi-wavelength storage was analyzed, and its model was established in this paper, with the disk reflectivity and the recording information distribution optional. The luminous power of the readout was divide into two parts: the part without the disturbance of other materials and the reading crosstalk. The expressions of them were presented, which were useful for the further analysis of the crosstalk and the crosstalk suppression method.

Silver oxide thin-films with various silver oxides concentration and silver particles amounts are prepared via magnetron sputtering techniques with oxygen reactive gas by varying deposition parameters. The presence of silver particles in the inorganic silver oxide compound was detected by x-ray diffraction. Heat measurements of the powdered silver oxide film via thermogravimetry analyzer (TGA) show that the powdered silver oxide decomposes and releases oxygen at a temperature of about 355°C. The oxygen concentration can be estimated by TGA weight loss. The optical reflectance and extinction coefficient of the silver oxide film confirm the dual function of the silver particles present in the film. The silver particles served both as the laser beam light absrober and reflectance centers for laser beam. With the presence of the silver particles in the silver oxide film, the reflective layer used in the prior art can be dispensed with. A single layer disk-silver dispersed silver oxide film, which served both as the recording layer and the reflective layer, deposited on the digital versatile disk-recordable (DVD-R) polycarbonate substrate is prepared. Since the plastic substrate is softened at a temperature of about 140°C, the silver oxide recording layer decomposes and releases oxygen when the recording medium is irradiated with a laser beam so as to permit formation of recesses in the plastic substrate and so as to permit a sharp change in reflectivity at positions where the recessions are formed. The characteristics of this single layer DVD-R disk are demonstrated.

The novel photochromism, diarylethene derivatives, 1,2-bis(2,5-dimethyl-thien-3-yl)perfluoro cyclopentene (1a) and 1,2-bis(2-methyl-5-carbonylphenyl)-thien-3-yl) perfluorocyclo pentene(2a) were synthesized. And the PC discs of these two diarylethenes were prepared by spin-coating and vacuum evaporating method. To some extent, the high density recording was carried out the multi-wavelength and multi-level optical storage system. On the PC disc, single-wavelength and eight-level recording was realized by 2a, and two laser beams of 532nm and 650nm were used in two-wavelength eight-level recording and readout simultaneously. The results show that the reflectivity differences between the recording region and unrecording region is greater than 50%. The creation is that the two-wavelength and four-step optical recording on the PC disc achieved first time.

In this paper, diarylethene derivative, 1,2-bis(2-methyl-5-N,N-dimethylaminophenyl)-thien-3-yl) perfluorocyclopentene (BMDTP) was synthesized. And the PMMA film of 10μm thickness of BMDTP was fabricated by spin-coating method. The maximal UV-Visible absorption of amorphous PMMA film is 634nm. And the reflective index modulation(Δn) is 2.14×10^-3 between the open- and close-rings form. On the PMMA film, ten gratings of hologram are recorded in one volume by angle multiplexing. Therefore, the diarylethene is a promising material for rewritable volume holographic optical storage.

Four novel photochromic dithienylethenes compounds, 1,2-bis[2-methyl-5(p-fluorophenyl)-3-thienyl]perfluorocyclo-pentene (1a), 1,2-bis[2-methyl-5(p-ethoxyphenyl)-3-thienyl]perfluorocyclopentene (2a), 1,2-bis[2-methyl-5(p-N,N-dimethylaminophenyl)-3-thienyl]perfluorocyclopentene (3a) and 1,2-bis(2-methyl-5-naphthalene-3-thienyl)perfluorocyclopentene (4a) were synthesized. Their optoelectronic properties, such as photochromism in solution as well as in PMMA amorphous, fluorescence and electrochemistry properties were systematically investigated. These dithienylethenes have shown good photochromic behavior both in solution and in PMMA amorphous film. All of them exhibited relatively strong fluorescence. With the increase of their concentration in a THF solution, their fluorescence spectra showed a bathochromic shift. The irreversible anodic oxidation of 1a, 3a and 4a occurred when performing cyclic voltammetry tests. Moreover, dithienylethene 1a showed remarkable multi-color electrochromic properties during the anodic polarization. In addition, photo-mode multi-step optical storage using 2a and 3a as recording medium was performed successfully.

The Center Aperture Detection (CAD) type Magnetically Induced Super-resolution (MSR) Magneto-optical Disk is one of method to overcome the limitation of optical resolution. For a reliability of the disk, it is important to investigate the stability of the magneto-static coupling between a readout layer and a recording layer through readout characteristics. In this paper, we tested the reliability of CAD tMSR magneto-optical disk. We used iD PHOTO disk for the CAD MSR magneto-optical disk. In the disk, the data is recorded on land and groove with a track pit of 0.6 µm and a bit length of 0.235 µm, by a method of laser pumped magnetic field modulation with an optical pickup of NA=0.62, λ=650 nm. The reliability was examined by PI error lines under the test condition of 80 °C-90 %RH. There were no considerable changes in read/write characteristics up to with an aging time of 2000 hour. The lifetime of the disk was estimated more than 7000 hour under the condition. By a method of the Arrhenius plots, we assumed that the lifetime of the disk would be more than 100 years under the condition of room temperature. We also confirmed that there were no significant changes in mechanical characteristics of the disks. These results show the disk using magneto-static coupling has sufficient reliability for consumer use.

IDE interface and SCSI interface are the most widely used in the storage device. SCSI bus supports I/O queue but storage device with SCSI interface is some expensive, while IDE bus does not support queue by itself but its price is more acceptable. In this paper, we just propose a twin-queue algorithm to benefit from the trade-off of the performance of the SCSI interface and the cheapness of the IDE storage devices. There are two priority queues, one for the host to respond client requests via SCSI bus, the other for the IDE storage devices where the requested data really locate. It is proved that the performance of the device with twin-queue algorithm is much higher than that of the normal IDE optical drive which is not equipped with our firmware using stochastic queue service model.

In this paper, we discuss a bus sharing architecture to implement a minimal unit for DVD jukebox. The bandwidth of host channel is usually tens times of the data rate of one disk. We integrate several DVD-ROM by sharing one ATA bus. It can fill the host channel by data transfer phase as much as possible. The shared ATA bus can be one or more to reach the bandwidth of host. And a queue and buffer algorithm to improve the performance of response time and synchronize is also introduced.

This paper considers the implementation of compensators for periodic disturbance cancellation, specifically applied to the removal of repeatable runout(RRO) from the position error signal(PES) in the high performance DVD player. The internal model principle is used for rejecting the sinusoidal disturbance caused by eccentric rotation of the disk, and the LQG methodology is used for the servo compensator design to improve the drive performance and meet the stability-robustness specifications in the frequency domain. A mathematical model of radial servo is constructed which forms the basis of a computer simulation. Simulation results are presented to show that LQG design is a viable approach.

This paper brings forward one concept of holographic storage of multi-level digital data at first. It is that each pixel includes more information than 1 bit, which means that a multi-level digital data image provides more information than a binary digital data image with the same pixels. So, the capacity will be increased with this technology. Furthermore, some aspects of holographic storage of multi-level digital data, such as the multi-level coding, storage characters and the quality of the stored image are debated. Finally, we research this holographic storage technology by experiment.

From CD to DVD to Blu-ray Disc, that optical disc all adopted the error-correction code to improve the storage. The error-correction code for the Blu-ray Disc, the up-to-the-minute optical disc, is more advanced than others. Many new technologies are applied in the Blu-ray Disc, especial the error-correction code which called Picket code is more powerful than RS and RSPC code. In the same condition, the error-code rate of the optical disc which used the Picket code is 1.5x10^-18, and the optical disc used RSPC is 5.7x10^-7. In this paper, the characteristic of those technologies which used in the optical disc will be discussed, include RS code used in CD system, RSPC code used in DVD system, and Picket code. Finally, it will add two different error matrixes to simulate the process of the error-correction code for the DVD system. In this simulating process, especially, we will compare the RS and RSPC code from mathematical direction in the simulation which is different from the professional comparison, this method can be easily accepted by beginner and the comparative result is very intuitionistic for freshman.

The data are stored in the alternative pits and lands for present optical disk, which is similar to the grating. Accordingly, the grating theory becomes the basis theory for the optical disk. The work presented in this paper focused on several aspects of the following: outlining the optical disk models adopted by the theories in print, analyzing the foundation basis of the models, and bringing forward a model which can be used for the new-fashioned optical storage, multi-wavelength photochromic optical storage. The classical scalar diffraction theory supposed that the effects of the optical disk on the incident beam were introducing the local phase delay that could be described by the optical path difference Δs, and the energy of the incident beam would not be absorbed. The two equations could respectively express the difference of the optical path: (1) Δs=n*Δh and (2) Δs=Δn*h. As the result of the analysis, we concluded that the tradition optical disk model fit for pit-land recording format and the cavity or bubble recording format. For the photochromic optical disk, the recording material, which absorbed the energy of the incident beam, was similar to the amplitude grating. The diffraction theory of this system was presented, and the equations for the readout signal were educed.

Zn ions were added into melts with 4.0mol.%, Fe ions were with 0.02mol.%, and In ions were with varying concentration of 0, 1.0, 2.0 and 3.0mol.%. A series of Zn:In:Fe:LiNbO₃ Crystals were grown by Czochralski technique. Their absorption spectra and photo-damage resistant ability were measured. The mechanism of the shift of OH- absorption peak was investigated. Their photorefractive properties were experimentally investigated by using two-beam coupling. The results shown that, the photo-damage resistant ability of Zn(4mol.%):In(3mol.%): Fe(0.02mol.%):LiNbO₃ Crystals were two orders than that of magnitude higher than that of Fe:LiNbO₃ crystals, and with concentration of Zn and In ions increasing, diffraction efficiency and response time of crystals were shortened. The experiment of associative memory were also carried out with Zn(4mol.%):In(3mol.%):Fe(0.02mol.%):LiNbO₃ crystals for the recording device and with Zn(4mol.%):In(2mol.%):Fe(0.02mol.%):LiNbO₃ Crystals for phase conjugation.

The interference of the surface plasmons polaritons (SPPs), localized SPPs, has been numerical analyzed by 2D finite difference time domain (FDTD) method. The near-field distributions of the localized SPPs have been presented. It is found that the quality of the output is not always good with strong interaction of the SPPs in super-RENS. It is also found that the near-field distribution and the output are almost changeless when the regions of the dark stripes have been adjusted.

The materials ratio is compounded followed by the molecular formula Ba_0.5Sr_1.5K_0.5Na_0.5Nb₅O₁₅. Doping 0.05 wt% CeO₂ and 0.03 wt% Co₂O₃ in KNSBN, Ce:Co:KNSBN crystal was grown by Czochralski technique adopting SiMo heater furnace. The exponential gain coefficient, diffraction efficiency and response time of Ce:Co:KNSBN crystal were measured through two-beam couple light path. The phase conjugation reflect efficiency and response time of Ce:Co:KNSBN and Cu:SBN crystals were measured by four-wave mixing light path. The holographic associative storage were established by using Ce:Co:KNSBN crystal as recording apparatus and Cu:SBN crystal as phase conjugation lens. Addressing was operated by 75% and 50% images and the associative storage reappearing images are clear, complete and noise was small. The photo-refractive effects of Ce:Co:KNSBN crystal are more excellent than KNSBN crystal.

The optical properties of the Ce:Cu:LiNbO₃ co-doped with different concentrations of In were measured, including absorption spectra, infrared transmittance spectra and holographic storage properties. The doped threshold of In was determined via the results of spectrum measurement. When the doped concentration of In is over its threshold, the photo-damage resistance ability of In:Ce:Cu:LiNbO₃ is improved dramatically. In the measurement of holographic storage properties, the response time of 34s, diffraction efficiency of 33%, and exponential gain coefficient of 18cm^-1 were obtained for In(3mol%):Ce(0.20wt%):Cu(0.015wt%):LiNbO₃ crystal.

In:Er:LiNbO₃ crystals with fixed Er concentration of 1mol% and variable In concentration of 1mol%, 2mol% and 3mol% have been grown by the Czochralski method, and then was made into waveguide substrates. The directly observing facula method was employed to measure the photo-damage resistance ability of the substrates, and it is found that In(3mol%):Er:LiNbO₃ has the highest photo-damage resistance ability among these three substrates. The structure was determined by the infrared transmittance spectra and the UV absorption spectra. The mechanism that the photo-damage resistance ability of the substrates increases with the increase of the doped concentration of In was discussed via the structure of the crystal.

The LiTaO₃ crystal doped with 0.03 wt% Fe₂O₃ was grown in a diameter-controlled Czochraski equipment using Si-Mo bar heater furnace. The photo-damage resistance ability, exponential gain coefficient, diffraction efficiency and response time of Fe:LiTaO₃ and Fe:LiNbO₃ crystals were measured. The measured results showed that the photo-damage resistance ability of Fe:LiTaO₃ crystal was as much as 5 times higher than that of Fe:LiNbO₃, the response speed of Fe:LiTaO₃ crystal was improved one order of magnitude than that of Fe:LiNbO₃, and the exponential gain coefficient and diffraction efficient of Fe:LiTaO₃ crystal were smaller than that of Fe:LiNbO₃, respectively. Using Fe:LiTaO₃ crystal as recording medium, the obtained image was clear and complete in the holographic associative memory experiment using self-pump phase conjugate reflector.

A series of LiNbO₃ crystals doped with different levels of In₂O₃ were grown by Czochraski method. The photo-damage threshold as well as infrared transmittance spectra and doubling frequency conversion efficient of the crystals was measured. At the same time, the shift mechanism of OH- absorption peaks in In:LiNbO₃ crystals were investigated. In the experiment of frequency doubling, it was found that the phase-matching temperature of In:LINbO₃ crystals was lower than that of Mg:LiNbO₃ and Zn:LiiNbO₃ crystals.

We report the near-field investigation on azobenzene contained polymer films using scanning near-field optical microscopy. Nanometer scale dots and lines were inscribed on these films, and the topographies and transmitting images of these patterns could be obtained at the same time. The transmitting images were in agreements with the topographies, and it proved that trans-cis isomerization of the azobenzene moieties in the illuminated area induced both surface relief and anisotropy. The experimental results helped to discover the mechanism of the photo induced surface relief and anisotropy, and the agreement between the transmitting images and the topographies could be applied in pure optical writing/reading in high-density data storage.

The servo control of the DVD optical head with tilt control is often difficult because of the coupled effect between the fine tracking servo and the tilt angle servo. Experiences show that the control system characteristics changes with different tilt angle. The controller may have to adapt for the characteristic change. This study presents a model to represent the changes in the system dynamics with respect to the different tilt angle. The variation in the dynamic behavior can than be lumped into a multiplicative system uncertainty. A µ-control synthesis procedure is then shown to be an effective servo design tool.

Potassium lithium niobate doped with CeO₂ and CuO, Ce:Cu:KLN crystals were grown by Czchralski method for the first time. The exponential gain coefficient of KLN and Ce:Cu:KLN crystals were measured. Effective charge densities of those crystals were computed. The exponential gain coefficient of KLN and Ce:Cu:KLN crystals are 7.4cm^-1 and 4.1cm^-1. The effective charge density exponential gain coefficient of KLN and Ce:Cu:KLN crystals are 3.2×10²²/m³ and 4.2×10²²/m³. The IR transmission spectra of KLN and Ce:Cu:KLN crystals were measured. OH- absorption peak of Ce:Cu:KLN shift red compare to that of KLN. The Raman spectra of those crystals were measured. The Raman spectra of KLN and Ce:Cu:KLN crystals were basically alike, which justified the fact that the ions of impurities entered into the lattice by replacement of original ions of KLN crystals.

A iSCSI-based CD mirroring server (iCDMS) has been developed and tested. Firstly, the iCDMS can automate to concurrently mirror multi- CD with multi- CD drivers, and the CD includes VCD, DVD, and so on. Secondly, the iCDMS can provide both of the file I/O and the block I/O services by an iSCSI module, which converges the NAS and SAN advantages, as high performance and data sharing across platforms. Thirdly, the iCDMS greatly improves the I/O speed by Zero Copy mechanism. Fourthly, the iCDMS implements automatically - allocating I/O bandwidth for different users and applications by enriching the metadata operating semantic of the CD server, and allocate a wider bandwidth for applications that has higher priority, changing the old average allocating bandwidth pattern. Finally, the iCDMS improves paralleled file I/O performance with a parallel FTP server module. In the experiments, the iCDMS has ultra-high-throughput for both of the file I/O requests and the block I/O requests

The optical reflectance and transmittance of Platinum oxide (PtO_x) and palladium oxide (PdO_x) mask layer, which are used to super-resolution near-field structure (super-RENS) disk, are investigated using Z-scan technique, under blue laser (442 nm) irradiation. The power thresholds of the PtO_x and PdO_x decomposition are obtained; the reversible and irreversible features for the two kinds of mask layers are cleared. Deformation in the micro irradiation region on surface of the mask samples, which is formed by decomposition of the PtO_x or PdO_x driving the Z-scan, is analyzed by means of an atom force microscope (AFM). The deformation analyses agree well with the Z-scan results. The optical features obtained at 442nm wavelength are compared with those at 532-nm wavelength, and the power threshold difference between the two wavelengths is also analyzed in detail based on irradiation power density and absorption spectrum of the mask samples.

The eccentricity in the Optical Disk Drive (ODD) is the inevitable deviation of the geometric center of circular tracks from the rotating center of the disk. The resulted “runout” in the drive is thus periodic with disk rotation. To overcome the runout, conventional approach is for the pick-up head to go forward to the target track while shaking with the period runout during track accessing. This paper proposes an integration of the learning algorithm to learn the runout motion with an on-line observer to estimate the track runout during track accessing. The purpose is to allow for online computation of the target track kinematics so that the controller can adjust the accessing strategy to accommodate for the target track behavior. The proposed algorithm is demonstrated to be feasible through experiments applied to the fine jump control for a general optical storage opto-mechenical-electrical-control plant from OES in ITRI.

Optical Disk Drives (ODD) uses chipsets to implement the various functions required in its operation. The chipsets always have fixed algorithm that make it impossible for the researches to carry out any experiments on newly developed algorithms. To overcome this difficulty, this study has constructed a test platform for the ODD experiments. This platform solution allows for software implementation of all the necessary functions in the CD/DVD system. The researchers can easily alter the software to change the existing functions of to implement new functions for different applications. The hardware of this development system is mainly composed of MSC-51, FPGA, DSK, AD/DA module, and an analog mother board. The MSC-51 is responsible for applying commands and setting functions, and it plays a role of master in the system. The TI DSK 6711, served as a slave, is responsible for implementing new algorithms and focus is mostly focused on servo control. The FPGA is responsible for handshaking among the DSK, the MSC-51, and the AD/DA module board; it also provides the register banks for the MSC-51 and the DSK. The purpose of the AD/DA module board is to establish communication link to the physical world. There are two A/D chips of eight channels and four D/A chips of four channels on the AD/DA module board. There are also a pre-amp chip and a driver on the analog mother board to amplify the signal on the ODD and to drive a DC motor. Users only have to change the pre-amp and ODD for different type of ODD.

The diarylethene may undergo photochemical ring-closing reaction and both photochemical and electrochemical ring-opening reaction. Irradiation of the open form with UV light results in essentially quantitative photocyclization to the deeply colored form. The dithienylcyclopentene derivative in their ring-closed forms can undergo ring-opening upon electrochemical oxidation.