This paper gives a review of the new progress in the super high-density optical storage research in China. The main research fields are short wavelength optical disk storage, near field optical storage, digital holographic storage and photo-induced multi dimensional storage. General remarks of the super high-density optical storage research are also given.

The mechanism of three dimensions digital data storage, including the construction of optical disk, seeking method, principle and method of reading/writing is described in this paper. With the technology of multi-layer, multi-color, longitudinal coding and masking, the new scheme can overcome the bottleneck of 3-D digital storage for tracking, focusing, data rate and do most of the advantages of 3-dimension optical storage for higher density and larger capacity.

Phase change technology has progressed from the original invention of Ovshinsky to become the leading choice for rewritable optical disks. ECD's early work in phase change materials and methods for operating in a direct overwrite fashion were crucial to the successes that have been achieved. Since the introduction of the first rewritable phase change products in 1991, the market has expanded from CD-RW into rewritable DVD with creative work going on worldwide. Phase change technology is ideally suited to address the continuous demand for increased storage capacity. First, laser beams can be focused to ever-smaller spot sizes using shorter wavelength lasers and higher performance optics. Blue lasers are now commercially viable and high numerical aperture and near field lenses have been demonstrated. Second, multilevel approaches can be used to increase capacity by a factor of three or more with concomitant increases in data transfer rate. In addition, ECD has decreased manufacturing costs through the use of innovative production technology. These factors combine to accelerate the widespread use of phase change technology. As in all our technologies, such as thin film photovoltaics, nickel metal hydride batteries, hydrogen storage systems, fuel cells, electrical memory, etc., we have invented the materials, the products, the production machines and the production processes for high rate, low-cost manufacture.

This paper describes market, application and technology of 3.5 in. Magnet-Optical (MO) as well as its future trend. The introduction of the GigaMO based on the MSR-media technology, is the key technology that will provide 2 approximately 5 GB per disk surface. With future technology, such as DWDD and MAMMOS, 30 GB/surface can be achieved. The floppy sized 3.5'MO will play very important role in new PC, TV and network environment.

Materials such as GeTe-Sb₂Te₃-Sb chalcogenide active layer, ZnS-SiO₂ fine grain structure (<2nm) dielectric protection layer and Nitrogen doped active layer realized million overwrite cycle characteristics. Phase-change optical disk produces PD, CD-RW and high density rewritable DVD in multimedia world. Phase-change technology, large reflectivity difference signal component has the capability of multi-level recording. Dual layer like volumetric recording technology and the wide wavelength response characteristics from near infra- red 780 nm to blue 400 nm has a capability of future high density recording performance around 100 Gbit/in² and more.

The principle and recent progress of super-resolution near- field structure (super-RENS) were introduced. Super-RENS is a unique method to retrieve optical near-field without any probes at high speeds approximately millions times faster than that of any other scanning near-field optical microscopes (SNOMs). First super-RENS disks were developed using an optically transparent aperture, and recently we found that a light-scattering-center using nano-explosion of silver oxide (AgOx) is also available in super-RENS.

The limitations of the conventional optical storage technology are first analyzed in this paper. The fundamental issues regarding terabytes optical recording are then discussed. Finally, the storage capacity of various approaches is presented.

Doped stoichiometric LiNbO₃ (SLN) crystals show more advantages over traditional congruent LiNbO₃ (CLN). This paper is focused on the measurement of the holographic performances of doped SLN crystals, including the sensitivity, dynamic range, and angular selectivity. The principles and methods for the measurements are first described, with more attention paid to the measurement of erasure time constants. The results show that the SLN crystal co-doped with Ce and Mn has the largest dynamic range, owing to the extremely long erasure time constants even by the multiplexing method. The SLN crystal co-doped with Tb and Fe and reduced in rich nitrogen atmosphere has the fastest response time and highest sensitivity. The oxidized and as-grown SLN crystals co-doped with Tb and Fe exhibit photochromic effect under UV illumination. With UV pre-illumination these crystals have sensitivity competitive to the heavily Fe doped CLN. The measured selective angles for most of the SLN samples of proper optical quality agree well with the theoretical calculation.

A Magneto-Optical disk system, named iD (intelligent, image) photo disk has been developed as a next generation media for digital still cameras. It has a large recording capacity, 730 MB with a 50.8 mm diameter. It employs the magnetic field modulation method for recording and Center Aperture Detection (CAD) type magnetic super resolution for reproducing. The media is designed to decrease the recording field so as to reduce electric power consumption for mobile use.

The MO properties of Co/Pt multilayers (MLs) depend fundamentally on the periodic structure of the multilayers. In this paper, the influences of Co layer thickness, the atom proportion of Co and Pt, and sputtering temperature on the MO properties of Co/Pt multilayers are studied. The results prove that the MO properties of Co/Pt multilayers strongly depend on the Co layer thickness and the atom proportion of Co and Pt. When t_Co < 0.4 nm, and t_CO/t_Pt equals 1/2, the multilayers have better comprehensive MO properties; when the sputtering substrate temperature is raised up to a proper degree, the crystallinity of the multilayers is improved and better periodic structure is obtained, which finally improves the MO properties of Co/Pt multilayers. We also studied factors which affect the T_C of Co/Pt MLs, and found that doping the Co layer with rare earth elements is an effective way to decrease the T_C of Co/Pt MLs, it might promote Co/Pt MLs into the stage of practical uses, but more detailed research work should be done further.

The temperature dependence of the amorphous Sm(Tb,Dy)FeCo quaternary alloys films was investigated using the mean-field model in combination with genetic algorithm. It is shown that when the light rare earth element Sm was substituted for the heavy rare earth element Tb or Dy, the compensation temperature (T_COMP) decreases, Curie temperature (T_C) remains unchanged and the saturation magnetization (M_s) at room temperature increases. Experimental data show good agreement with the calculated results.

Pt-Co alloy thin films wre prepared byDC magnetirons puttrngusng Pt-Co alloy targt andcomposite targt. It was found tht the highsputtering pressur and sutiable substrae temperatur we ethe key toacquireperpendicuarlamagnetic anisotpry (PMS) in Pt-Co alloy films. The large ptential Keer fcoefficient was obtained not only at short wavlengthr ginbut over the whole spectral reginfrom 300 - 800 n.the orignof PMA was alsodisussed.

Thermal stability of amorphous TbFeCo monolayers and {TbFeCo/Pt} multilayers is studied by magnetic viscosity measurements M(t). Using, isothermal remanence measurements the relationship between the magnetization reversal process and its time dependence has been investigated. The non-linear evolution of magnetization with ln(time) happens when the mechanism responsible for magnetization reversal process is mainly domain nucleation. On the other hand domain wall motion process induces a linear M(t) behavior. For multilayers with very small Pt thickness (samples with high square hysteresis loop), magnetization time decay can be described easily by a single energy barrier E_B model. As Pt thickness increases, distribution of E_B becomes wider leading to almost linear magnetization decay with ln(time) as in longitudinal recording media. The activation volume is determined for these media and shows a strong correlation with reversing field, thus yielding variations of stability over a written bit.

A thin SiN layer was coated upon GdFe/Si film in order to avoid the surface contamination and oxidation. From the SiN/GdFE interface, the genuine optical constants of GdFe layer were obtained using spectroscopic ellipsometry. The magneto-optical Kerr effect in the large energy range between 1.6 eV and 4.5 eV was also studied. Calculations show that the MOKE peak in the high energy range originates not only from its intrinsic magneto-optical characteristics of GdFe layer, but also from the interference of SiN layer. When the Fe content decreases from 79.3 to 75.8 at.%, the sign change of the complex Kerr rotation was observed and found being induced by the spin-flip.

Measuring mechanical characteristics of optical disk is very significant. This paper compares the existing measuring methods and gives a novel method we adopted in details. Some measuring results are also shown.

AlN_x/DyFeCo films were deposited on glass substrates by magnetron sputtering and reactive rf magnetron sputtering. The influence of AlN_x coverlayers on DyFeCo magneto-optical media was studied. The results show that nitrogen surplus in AlN_x leads to changes in the MO behavior of DyFeCo films due to the reaction of Dy with nitrogen. Furthermore, the influence of thickness of AlN films on the coercivity, anisotropy and eigenvalue of Kerr rotation angle of RE-TM films was investigated. The results can be explained based on the internal stress, impurities and the pinning of defects induced by 'peening effects' of high-speed atoms.

A fatigue behavior measurement system for the magneto-optical recording films is designed. In this system, a kind of TRIAC- based L-C series resonance method is proposed and the intensity dividing readout method is adopted to eliminate the fluctuation of the readout laser power.

The genetic algorithm has been adopted to optimize the structure of magneto-optical disk. The results show that this method has advantages over the traditional method such as less constraint, implicit parallelism and global optimization. Additionally, we can get a set of results, not just only one, and the second time optimization can be proceeded based on the first.

The large transmittance change induced Zn-Ga-In oxide films grown by the sputtering method was investigated in the wavelength near 400 nm. The ability to record on the Zn-Ga-In oxide films, using THG of YAG laser ((lambda) equals 355 nm, 3 ns) was confirmed.

A simulation model with spreadsheet to analyze the crystalline structure and the crystalline grain size in the recording layer has been investigated. The temperature dependence of crystallization pattern are calculated basing the Fractal theory (Cell-Automation Rule).

The method of estimating the reliability of recordable phase change media is examined. The PD disks of 650 MB in total capacity in 12 cm diameter are used as experiment samples. The media are put under the acceleration environment of 80 degree in the temperature 85% in humidity, and change of BER is observed. Two kinds of life (archival and shelf) are tested. As for the disk to be examined, it is necessary to do the acceleration reliability test in a linear area in the destruction limit. Therefore, there is a limit in a possible acceleration coefficient. In the optical disk with long life at present time, it will take extremely long time to presume the final life. In this thesis, the method of estimating the life of a long-lived disk at shorter time is discussed.

Effects of preparation parameters on the optical constants (n,k) of Ge₂Sb₂Te₅ thin films in the wavelength range of 300 - 830 nm were studied. The results show: (1) When the sputtering power is constant, the refractive index (n) first increases and then decreases with increasing Ar gas pressure, whereas the extinction coefficient (k) changes with Ar gas pressure in a contrary way to that of n. (2) When the Ar gas pressure is constant, for the amorphous thin films in the wavelength range of 300 nm - 500 nm, the refractive index (n) first increases and then decreases with increasing power, whereas the extinction coefficient (k) decreases monotonically. In the wavelength range of 500 nm - 830 nm, the refractive index (n) decreases with sputtering power, while the extinction coefficient (k) first decreases and then increases. For the crystalline thin films, in the wavelength range of 300 nm - 830 nm the refractive index (n) first decreases and then increases, whereas the extinction coefficient (k) decreases. (3) The extent of the influence of preparation parameters on n and k also changes with wavelength, it is greater in the long wavelength region than in the short wavelength region. The mechanism by which the optical constants of the Ge₂Sb₂Te₅ thin films are affected by the preparation parameters is analyzed.

The effects of thermal treatment on the dependence of optical constants on wavelength and the changes of optical constants of GeTe, Sb₂Te₃ and Ge₂Sb₂Te₅ thin films at different annealing temperatures are studied. It can be found that the optical constants of GeTe, Sb₂Te₃ and Ge₂Sb₂Te₅ thin films change with increasing annealing temperature. The crystallization speed changes with increasing Sb content, i.e.: the crystallization speed of GeTe < the crystallization speed of Ge₂Sb₂Te₅ < the crystallization speed of Sb₂Te₃. The mechanism of the change of the optical constants of the GeTe, Sb₂Te₃ and Ge₂Sb₂Te₅ systems due to thermal treatment is also analyzed.

Organic material with pronounced thermochromism is used as a mask layer in a phase change optical disk. The thermochromic material exhibits significant change in optical properties at increased temperatures as well as fast response upon pulsed laser irradiation. Recording and retrieving signals from marks smaller than that of the diffraction limit is investigated under high speed disk rotation.

AgInSbTe phase-change films were deposited on K9 glass substrates by RF magnetron sputtering technology using a Ag- In-Sb-Te alloy target. The as-deposited films were annealed at 300 degrees Celsius. The influence of background pressure, sputtering gas pressure and sputtering power on the optical properties of the phase-change films were investigated. It was found that the optical properties of the phase change films were synthetically affected by the sputtering parameters. It is disadvantageous to the optical properties of the films when the sputtering gas pressure and power are too high or too low. Lower background pressure, proper sputtering gas pressure and sputtering power are very important to producing the phase- change films with good properties.

The optical constants of phase-change films are assumed to be constant regardless of film thickness in conventional optical design and thermal simulation of multilayer structure optical disks. However this assumption is not valid when the phase- change film thickness in the optical disks becomes very small. In this study, the dependence of the optical properties on the thickness of AgInSbTe phase-change films was investigated. The reflectivity, absorptivity, thickness and optical constant of the films were measured. The change of the extinction coefficient and refractive index become significant when the film is very thin, and become larger at shorter wavelengths such as in the blue and green region. These results are very useful in improving the accuracy of optical design and simulation of AgInSbTe phase-change optical disks, as well as in the study of phase-change optical disks at shorter wavelengths.

Monolayer Ag-In-Te-Sb-O thin films were deposited by reactive RF-sputtering using Ag₈In₁₄Te₅₅Sb₂₃ alloy target in a mixed argon-oxygen plasma at different partial pressure ratio of oxygen to argon (P₀₂/P_Ar). The optical properties of these films were studied. It was found that films deposited at P₀₂/P_Ar of 2 to approximately 4% had comparatively large absorption in the wavelength range of 400 - 650 nm. After annealing at 300 degrees Celsius for 30 minutes under protection of argon, the reflectivity in the wavelength range of 500 - 700 nm could rise by about 18 - 25%. The optical constants (n,k) also changed much after heat treatment. XRD analyses indicated that the changes were attributed to the crystallization of Sb. The reflectivity contrast can be as high as 20% after being recorded using short-wavelength laser beam (514.4 nm) with low writing power (10 mW) and short pulse width (100 ns). The film also exhibits certain erasability. This kind of films possess the potentially for use in high density optical storage.

The film thickness of optical disk multilayer is difficult to be precisely controlled in the actual coating process. The thickness error becomes a main factor influencing the optical characters of the film system. The thickness error sensitivity factor of dielectric optical multilayer is derived from the optical matrix in this paper. The applications to recordable and phase-change optical disk systems are given. The effect of the thickness error on the reflectivity or reflectivity contrast of the optical disk multilayer is analyzed with a computer numerical calculation. The sensitivities to thickness error for different layers or in different film-thickness ranges are compared and discussed. A sketchy method of defining allowable thickness error is given. These results have guidance significance to the design of film layer and the optimization of coating technology in the optical disk systems.

The method and the device, which initializes phase change media standardized by formats of such as CD-RW, record type DVD and etc., are discussed. In these media it should be a state of the crystal phase with high reflectivity before recording. It is necessary to change into the crystal phase from amorphous phase in a usual state of as-depot. The method to scan the laser spot beam of the oval shape that could be processed by a more high-speed, slighter control was examined. Because the life of laser and the scanning speed of beam spot are important factors that influenced the processing cost, the life of the laser and the improvement of the process speed are considered. The most much relating to the quality of media of finished products is near field pattern of the laser. Initializer in the mechanism, which can be used in the mass production line, is designed.

Thin films of tetra-neopentoxy phthalocyanine zinc (TNPPcZn) were prepared from its toluene solution by spin-coating technique. Their structural changes due to heat treatment were characterized by the change in optical absorption. The static rewritable optical storage performance of these thin films with recording wavelength at 632.8 nm was investigated. Under the selected writing and erasing conditions, 35 cycles was realized in the static measurement. The reflectivity contrast was in the range of -20% to approximately 20%.

A series of metallized thiazolylazo dyes have been designed and synthesized. Smooth films on optical glass and single- crystal silicon were prepared by spin-coated method. The UV- Vis absorption spectra of the dyes were measured in solution and in films. The optical constant (complex refractive index N equals n + ik) of the films on single-crystal silicon has been determined using scanning ellipsometer. The variation of the complex refractive index N with wavelength (lambda) was obtained. Thermogravimetric analysis (TGA) and differential thermal analysis (DTA) of the nickel thiazolylazo dye showed clear threshold of thermal decomposition with a sharp exothermic park. Static optical recording tests were carried out. The results show that the nickel thiazolylazo dye is more suitable for use in short-wavelength diode-laser optical recording.

Phthalocyanines (Pcs) are widely investigated compounds for optical storage applications, especially used as recording media of CD-recordable. As a novel class of Pc-related compounds, Subphthalocyanines (SubPcs) share many of the excellent properties of Pcs such as thermal and chemical stability and at the same time have some specific characteristics due to their smaller number of coordinated ring and near-planar cone-shaped geometry. The spectral and optical properties of a new trinitro-substituted SubPc have been studied. Films were prepared either by vacuum evaporation or spin coating from a solution in poly(methylmethacrylate) (PMMA). The UV-vis spectra (absorption, reflection, transmission) and optical constants (refractive index, extinction coefficient) of the sublimed film were measured by a spectrophotometer and an ellipsometer respectively. We also measured the static optical recording performance of this film with a thin Al reflective layer on it. These results demonstrated that SubPc has a strong and broad absorption region near 600 nm and it will be a promising candidate for short-wavelength optical recording (such as DVD-R) if the high-quality films can be got.

1,2-bis(2-methyl-5-(4-methoxyl-phenyl)thiophene-3- yl)perfluorocyclopentene was synthesized by the elimination reaction of perfluorocyclopentene with butyllithium. The UV- Vis absorption spectra of both the open form and the closed form were detected. Their geometries were optimized by PM3 method, and ZINDO/S CI method was employed to calculate their UV-Vis absorption spectra, which were consistent with the experiments. Three fabricated dithienylethene derivatives linked by heterocyclic pyridinium betaines were investigated by the same methods to calculate their UV-Vis absorption spectra of both the open and closed forms. The results show that reading at the wavelength above 700 nm will not destroy the recorded information. Thus a non-destructive method is constructed on these diarylethene molecules.

A new cyanine dye thin film has been prepared for high-density digital versatile disc-recordable (DVD-R) by means of a spin- coating process. The effects of the optical and thermal properties of the cyanine dye on the recording characteristics were studied. Rapid decomposition of the cyanine dye in a narrow temperature range, which is critical to the clear mark edges, is shown in this paper. A steep absorption edge at the 635 nm is crucial to high reflectivity. The optical recording performance of the cyanine dye thin film shows that high reflectivity contrast (48%) can be obtained at low writing power and narrow writing pulse-width using He-Ne laser (632.8 nm) irradiation. The carrier to noise ratio (CNR) of the single layer disk is greater than 40 dB at the traveling rate of 2.4 m/s.

In this paper, two-photon bit data storage in azobenzene polymer liquid crystal (PLC) film using low-power continuous wave (CW) laser beam at 532 nm is proposed and demonstrated for the first time, the exposure threshold of the material is below 4 X 10⁶ mw/cm², and a bit data storage pattern is recorded by two-photon absorption (TPA). The data is easily erasable and rewritable by the light of the same wavelength as the recording light.

Novel bisthienylethene-based photochromic material (TAP-BTE), in which four bisthienylethenes link on the ring of tetraazaporphyrin, has been synthesized. This kind of macrocyclic-linked bisthienylethenes has demonstrated better ring-closing quantum yield and has higher absorption cross- sections (1.65 X 10⁴ M^-1cm^-1). The optical switch and fatigue resistance properties of the novel photochromic material have been investigated. The results showed that TAP-BTE has a thermally gated reactivity, and is useful for non-destructive readout when it is used as the memory medium.

Subphthalocyanines (SubPc) are composed of three isoindole units containing boron inside, which defines a molecular axis and forms a cone-shaped structure. Despite being non-planar, they show a delocalized 14(pi) -electron system similar to that present in phthalocyanines. The attractive characteristics of SubPc are their chemical stability and thermal stability. We report here the synthesis of three SubPc compounds, in which the axial substituent is a bromide. The peripheral substituent in the compounds leads to an improved solubility in common organic solvents. The results demonstrated that SubPc showed a strong and broad absorption region near 600 nm. This is advantageous for the purification and important for the applications in optical storage (DVD-R).

Based on a blue diode laser (405 nm wavelength) and a two- element objective lens with a numerical aperture of 0.85, a third generation optical recording system has been developed that is able to record 22.5 GB on a single sided 12 cm diameter disc, at a user data rate of 50 Mb/s. The system is referred to by the technical name DVR for high definition Digital Video Recording. In this paper, we review the physical and the system concept, the phase change media, the optical pick up unit, and the drive implementation.

The development of a production Electron Beam Recorder designed for making masters for optical discs of up to 50 gigabytes capacity is discussed. A low cost upgrade path for mastering discs of capacities of 100 GB or higher is shown and some recent results of optical discs ranging in capacity from 4.7 GB to 45 GB are presented.

Optical near-field recording with a super-resolution near- field structure (Super-RENS) records and retrieves small marks with dimensions beyond the diffraction limit. A thin layer of an antimony (Sb) film, added to the usual phase-change optical disk structure, is the key material of this technique. We investigated the nonlinear optical properties of the Sb film, especially the optical switching behavior in the stationary state using a nanosecond pulsed laser. Clear switching was observed under microscopic measurement. Time response of the optical switching properties were examined and found to show fast rise-up and slow decaying times.

We describe the angular dependence of near-field signals generated in super-resolution near-field structure (Super- RENS) disks. The carrier-to-noise ratio (CNR) of transmitted signals using different numerical aperture's (NA's) lenses, were mostly the same values, experimentally. While on computer simulation by finite-difference time-domain (FDTD) method, it was found that most scattered signals were trapped around the optical axis.

Scattering-mode super-resolution structure (Super-RENS) is an alternative to realize high-density optical data storage. Ag doped GeSbTe films were investigated to optimize the high- density optical data storage characteristics. It was found that the readout durability could be greatly improved by Ag doped GeSbTe films.

High density and high data rate are two key points in the development of optical data storage. The aim of this contribution is to report the ultrahigh density recording based on third-order non-linearities (TONL). Studies on the laser beam intensity-dependent refractive-index changes of TONL media, either organic or inorganic, were carried out on the basis of classical electromagnetic field theory. The graphic solutions of the theory and the experimental evidence indicate that materials with large susceptibilities, (chi) ⁽³), and ultrafast response due to dispersive-NL or saturated absorption-NL have good optical switching properties which can be described by an- or multi-optical hysteresis loops and used as the mask layers of super-RENS (Super- resolution near-field structure). On the other hand, the numerical solutions of the wave functions give the third-order nonlinear optical dynamics of direct-gap or indirect-gap semiconductors due to band-filling effect or photon-excited electron-hole generation and recombination processes. Based on TONL, an optimized structure for ultrahigh density recording can be designed. Using miliwatts in power, picosecond in response and having the spot size in the range of n (1 approximately 5) yields 10 n nanometer, these well-designed media are now physically possible in practice.

The optical properties of glasses irradiated by high-power, 810 nm femtosecond laser have been studied. Laser-induced processes occurred at irradiation well below the threshold for laser-induced damage. The visible absorption spectra of the original and irradiated glass were measured and darkening lines were found in the irradiated region. According to absorption spectra, the absorption of glass was increased greatly after irradiation by femtosecond laser. The absorption of the irradiated glass decreased along with time and reached stabilization in about 90 minutes. The laser-induced darkening in the glass disappeared when the glass was heat-treated under 200 degrees Celsius for a few minutes. It was considered that darkening was induced by color-center formation because of glass matrix photoionization and the consequent trapping of electrons and holes by intrinsic or impurity defect of the glass. This process is expected to become a useful method used to fabricate optical memory with both an ultra-high storage density and an ultra-high recording and readout speed.

The optical characters and light wave propagation of various fiber probes, solid immersion lens (SIL) system and Super-RENS for near-field optical recording are numerically simulated using 3D finite-difference time-domain (3D-FDTD) method in this paper. The aperture metal-coated probe have a near field spot size smaller than the bare-glass fiber probe, which means higher data density in near-field optical recording. The entirely metal coat probe is pointed out to have an extremely small near-field spot size about 10 nm, but the output electromagnetic wave propagation decrease to nearly zero within a few nanometers. The propagating and evanescent wave in different solid immersion lens (SIL) system is numerically simulated. The spot sizes are different because of different polarization. With the TbFe substrate, spot size will remain constant as observation distance z increased. But the propagating, evanescent and total energy decay more rapidly than the SIL system without TbFe substrate.

In this paper, we describe the upgrade of Laser Beam Recorder (LBR) for wobble grooves required by CD-R from the existing CD mastering system, and report the results on CD-R mastering and stamper testing. CD-R discs conforming to the requirements of Orange Book have been successfully produced with self- developed stampers on a CD-R disc production line. The tests were accomplished on both unrecorded and recorded discs for further stamper quality verification.

Atomic force microscope (AFM) is an invaluable measurement tool for analyzing the sub-micron and nanometer-level detail because of its ease of use, three-dimensional measurements and minimal sample preparation unlike TEM and SEM. So AFM can be used for both qualitative and quantitative information in optical storage science and technology. Its imaging can provides characterization of optical disc media with almost non-destructive. In CD-R manufacturing process, groove geometry structures of stamper, substrate and discs are very critical. In our experiments, pre-groove shape parameters (width, sidewall angle, depth and roughness) of many kinds of CD-R stampers (depth from 70 nm to 240 nm) were studied by AFM. The recorded bits on CD-R disc were observed and analyzed.

The out-radial movements of pickup head in optical data storage systems are studied, and its influences on Push-pull track error signals and Differential Phase Detection (DPD) track error signals are analyzed.

For recordable media, pre-format must be embedded into the discs. CD-R system adopts a unique addressing technology called ATIP to meet this requirement. ATIP represents the Absolute Time In Pre-groove. In this paper, an ATIP test system for 4X is described. All the parameters related to the wobble pre-groove including wobble CNR, wobble amplitude, ATIP Error Rate (ATER) and ATIP Burst Error Rate Length (ABERL) can be measured using this system.

The process of replication, such as molding, clamping, injection, metalizing, even extrusion and printing, put an important impact on the quality of the finished DVD discs. They are crucial to duplicator, but not so easy to detect by conventional analysis methods provided by current commercial off-line tester. We introduce a data-analysis method to enlarge the effects of replication process on the disc parameters, by means of eliminating the disturbance from pre- replication process. This method is named RES (Remainder Elimination of the effect Stamper) parameters. An example is given to show the status of disc's edges affected by molding, and the selection of different molding patterns is analyzed.

The dependence of readout signal from embossed grooves on edge decline is studied by a simulation method. The disk is modeled as one-dimensional grating that consists of grooves with declining wall. The formula of readout signal is derived based on vector diffraction theory, then the effect of the wall decline is investigated. The simulation shows that the effect of wall decline depends on the polarization of incident light. When the electric vector of the incident light is perpendicular to the groove wall, the decline mainly influences the peak-valley value and the increasing rate of the readout signal. When the electric vector is parallel with the groove wall, the decline mainly influences the amplitude of readout signal.

We introduce a homemade testing system for groove geometry of CD-R substrates by measuring diffraction orders. This testing is of particular importance in CD-R disc manufacture process because the results fed back from the testing can be used to help optimizing recording, developing, metalizing, electroplating and replicating processes. Even if the width and depth of groove are not accurately obtained by this system, it is also valuable in CD-R disc manufacturing process because the system is simple, sensitive, quick and non- destructive, and can be well-used to judge the quality of substrates. The results of the same sample tested by our system and an AFM microscope are presented.

Jitter is defined by the variation of each pit length and timing variations between data and clock frequency on discs. As a comprehensive item, it relates with error rate directly. In this paper, the definition, determined and influence factors of jitter n are analyzed. According to the analysis, measurement methods of jitter are provided. The precision of a method. The method's precision and demand are calculated and explained in detail.

The next generation digital versatile disk (DVD) which uses blue laser will have a capacity of 13 Gbytes to 15 Gbytes. Compared with the current DVD, the wavelength will be shorter and the NA will be higher. But with the increase of NA and decrease of wavelength, the depth of focus (DOF) decreases rapidly, which makes it hard to track by the servo-system. In this paper, we propose to use an optimized three-portion phase-shifting apodizer to increase the depth of focus and at the same time minimize the spot size, which makes the DOF of next generation DVD comparable to current DVD. The simulation results show that an optical system with this apodizer also has a good defocusing characteristic.

In this paper, the objective of servo system in an optical disc player is discussed. The traditional servo method, zero- order indifferent PID adjustment, is analyzed. Based on the analysis, a new servo system, 1-order indifferent PI&PID adjustment, is provided. In the new adjustment method, the main error of low frequency from ECC and Imbalance will be reduced to minimum in theory. In the end of the paper, the stability of the new servo system is analyzed in detail.

The principle of modified repetitive control is analyzed. According to the model of tracking actuator, a simplified design method of modified repetitive control was introduced. The simulation result shows the modified system has good performance. Compared with classical control system, it increases servo accuracy and steady state robustness, decreasing error signal greatly.

Thin film of Ag₈In₁₄Sb₅₅Te₂₃ was prepared by RF-magnetron sputtering method, and the organic dye (phthalocyanine) thin film was prepared by spin coating. Micro- and submicro-size changes induced by laser irradiation on the film were studied by atomic force microscopy (AFM). The characteristic of recorded spots topography is related by recording condition (laser power, pulse width etc.) and properties of material (phase-change or shape-change). The mechanism of microstructure formation is discussed.

The constantly increasing demands for more storage capacity and better performance require regular upgrades of the actual standards and -- from time to time -- completely new standards. Especially during the last couple of years, a number of new standards have been introduced and this trend will continue.

Rewritable DVD (DVD-RAM) 4.7 GBytes products such as DVD-RAM disc, DVD-RAM drive, and DVD Video Recorder have been developed. DVD-RAM can integrate all Audio, Video, Imaging, Computer, and Network applications with write compatibility between DVD-RAM 2.6 GBytes and read compatibility across the entire DVD format family. DVD-RAM disc and drive technologies such as high speed reliable recording, easy operability, secure copy protection functions, and DVD Video Recorder are presented. With the coming of blue light sources, the capacity of the DVD-RAM disc can be upgraded 3 to approximately 5 times, and furthermore could be expanded over 10 times in conjunction with a high-NA optics and a dual-layer disc technology, then 2 to approximately 4 hours high-definition video will be recorded.

Optical Discs are currently finding new mass applications in computing, web usage and entertainment. In only 5 years the CD-R consumption has grown from basically zero to over billion discs this year; the video DVD is very successful in the US and now starting in other regions; video recording on disc is on the horizon. Thin film deposition is among the key production technologies for the production of all of these formats. While in established fields such as CD-R production the emphasis is on productivity, other formats from DVD-9, SACD or the higher density rewritable formats require innovation in materials and process technology. This paper takes a closer look at these challenges for the different formats and discusses the current status of thin film processing of Optical Disc formats.

A review of recent developments in CD-R technology is given. This covers the physical design principles of the disc together with its production methods. We review all the subsequent manufacturing steps. The relevance of groove replication, substrate conditioning, dye solution and solvents, spinning methods, dye coating process conditions, dye layer drying, sputtering and lacquer coating on the CD-R disc performance are presented. The differences in the recording mechanism for several types of dyes are illustrated. The two modified new phthalocyanine and cyanine processes are described. Some technological implications for higher density recordable formats like DVD-R will be given.

It is necessary to improve optical, geometrical, and mechanical properties in the optical disk substrates as the information storage devices with high storage density using short wavelength lasers are being developed. However, the conventional injection molding process is no longer appropriate for producing the high-density information storage optical disk substrates with superb optical, geometrical, and mechanical properties. It is, therefore, inevitable to develop new concepts for the molding processes. In the present study, DVD-RAM substrates were fabricated by injection-compression molding, which is regarded as the most suitable process to manufacture optical disk substrates. The effects of various processing conditions on the birefringence distribution, the land-groove structure including the groove depth and the surface roughness of the land, and the radial tilt were examined experimentally. It was found that the birefringence, which is regarded as one of the most important optical properties for optical disk, was very sensitive to the mold wall temperature history. Also, the integrity of the replication, represented by the land-groove structure, and the radial tilt were influenced mostly by the mold temperature and the compression pressure.

It becomes more and more important to search for a suitable process window for CD-R production because CD-R's performance will vary with the thickness of the recording material (dye layer). With the development of CD-R writer, it is strongly recommended that CD-R should be compliance with multi-speed recording strategy. For different kinds of dyes, we need to re-design the pre-groove geometry of stampers and dye/solvent formulation for getting good CD-R's performance. In the meanwhile we need to use different methods to search for the process window according to the characteristics of the dye. For the Irgaphor Green phthalocyanine dye, BLER will increase with the reducing thickness of the dye layer at lower writing speeds; Jitter will increase with increasing thickness of the dye layer at high writing speeds. So we define the process window as the optical density when BLER is 100 at low writing speed and L3T Jitter is 35 ns at high writing speed. For the Irgaphor Supergreen phthalocycnine dye, BLER is not sensitive to the thickness of dye layer and normally I11 is too low at lower writing speeds. After finalizing a stamper, we increase I11 by increasing the thickness of the dye layer and decrease L3T jitter by decreasing the thickness of dye layer. So we define the process window as the optical density when I11 is 0.58 V at low writing speed and L3T Jetter is 35 ns at high writing speed. The temperature and humidity have certain effect on the dye layer thickness, the process control is benefited by the wider process window. Using the above methods, we could easily establish the CD-R process window and set the optimum dye layer thickness during the CD-R production with the Ciba phthalocyanine dyes.

This paper describes the structure of Personal Optical Disk Library (PODL), a kind of large capacity (40 GB) optical storage equipment for personal usage. With the knowledge engineering technology integrated in the PODL, it can be used on knowledge query, knowledge discovery, Computer-Aided Instruction (CAI) and Online Analysis Process (OLAP).

The software industry loses billions of dollars each year due to software piracy. And CD-ROM technology is one of the most successful and fast growing methods for quickly and economically distributing information. So it is an urgency to find a good method to protect CD-ROM from being pirated. In this chapter, we will discuss some new technologies of anti- piracy. According to these discussions, we will put forward our new anti-piracy method.

How an eight-terabyte CD-ROM storage system could behave as a standard CD-ROM peripheral device without a specifically designed device driver on any operation system is discussed in this paper. Because normal tertiary storage systems can hardly hold a capacity with terabyte magnitudes, so a new file system based on Small Computer System Interface (SCSI) is presented, which can address as many as eight-terabyte storage memories. An experimental system called 'Virtual CD-ROM' system of this idea is discussed, and some techniques critical to the fulfillment of such a system are considered.

We report on a novel micromachined sensor head for optical data storage devices. The head is based on a 6 X 6 aperture array with subwavelength dimensions. In comparison to previously introduced flat-aperture heads, a tip-based array is presented which profits from a recently presented reliable fabrication process of apertures in the 100 nm regime and below. This fabrication process exploits inhomogeneous thickness distributions and modified etching rates of thermally generated siliconoxides on <001>-oriented silicon wafers at relatively low temperatures, and makes it possible to open apertures with dimensions below 150 nm in hollow SiO₂ pyramidal shaped tips. A metallization process is finally used to provide optical opacity and to further reduce the overall aperture dimensions to less than 100 nm. The fabrication process of these sensors is described in detail and the results are confirmed by SEM photographs.

In this paper, a new kind of automatic method to test the Parameters of CD/DVD Optical Discs is introduced and named near-line inspector. Being connected to product lines, sampling and testing the discs automatically in batches, our inspector can provide a brief yet revealing profile of optical disc parameters such as electrical variables (HF, Jitter, etc.), physical variables and digital error variables in an acceptable short time so as to reflect the up-to-date condition of the product lines. As a real-time and relatively high-efficiency measurement method, it will be integrated into a perfect test system together with on-line and off-line inspectors. Such a system would be especially suitable for the replication of high-quality optical discs in large volume. The layout of the whole set of test system is described. The feasibility and reliability of near-line method are analyzed based on study by means of a high-precision DVD off-line test system developed by us.

A magneto-optical storage card is produced using magneto- optical recording medium. The magneto-optical card consists of a substrate and a multilayer film structure. The card substrate has the groove geometry pattern comprising the track pitch, the groove width, and the groove depth. As the magneto- optical recording medium, the RE-TM magneto-optical recording material is used. The card substrate is made of glass, on which the preformatted pattern is formed by a photolithography technology, the preformatted pattern is used for servo tracking and for pre-recording information for optical data storage. The prototype drive system for the magneto-optical card is capable of driving, writing/reading and erasing the MO card. The card has high reliability for information storage.