This presentation outlines the aim of the BD-ROM standard and the design policy and introduce examples of specific functions

We present an optical card reader optimised for robustness in portable applications. Parallel readout and minimal mechanical movement are key ingredients of this system.

The format of a 8.5 GB double-layer recordable DVD disc is described. The main physical parameters ans aspects of the logical format are presented.

We developed a 25GB ROM disc whose substrate is made of paper. Structure of the disc is based on the Blu-ray Disc format. We improved mechanical characteristics of a paper core by introducing a symmetrical multi-layer structure. The signals in the paper disc were reproduced successfully and the jitter values were less than 6%.

Mode index lenses for light delivery as part of as optical recording system were designed and tested. The measured spot size is 2.2 micron at the exit.

In this paper we describe the fabrication of dielectric optical tantala and titania waveguides on AlTiC sliders.

Heat-assisted magnetic recording (HAMR), also known as hybrid recording, is one of the technologies proposed for extending hard disk drive areal densities beyond a Tb/in². Due to their planar nature and compatibility with existing hard disk drive head fabrication techniques, dielectric optical waveguides have been suggested as a means for delivering light directly to the recording medium or near field optical transducer. In this paper we present spin stand experimental results from a dielectric optical slab waveguide fabricated on an AlTiC slider.

We improved the electron beam recorder with a differential pumping head for higher density discs and mass production. The beam diameters were improved by exchanging the aperture size of the objective lens and beam stability were also improved by adding a sound proof case. As for the performance of the improved electron beam recorder, we showed that a 104Gb/in² (150GB capacity/layer) density disc with EFM plus modulation codes can be fabricated. We also improved the pit shape uniformity and a margin of the process by introducing the appropriate write strategy that is simulated by the Monte Carlo simulation to the recording pulses.

We report on the technical progress in increasing the recording density of optical storage systems by means of improved read-channel signal processing and write-channel optimisation. The recording density increase is realized by employing PRML (Viterbi) bit detection in combination with improved timing recovery and adaptive equalisation algorithms, and by using a signal quality characterisation scheme which enables a proper control of the write process in the considered range of storage densities. The Blu-ray Disc (BD) optical disc system employing blue-violet laser with the wavelength of 405nm, objective lens with numerical aperture of 0.85 and disc cover layer thickness of 0.1mm is used as an experimental platform in our present study. Multi-track experimental results for both single-layer read-only (BD-ROM) and single-layer rewritable (BD-RE) media are presented to show the feasibility of the increased-density BD.

A Partial Response Signal-to-Noise Ratio (PRSNR) and a Simulated bit Error Rate (SbER) are introduced as measures to evaluate a signal quality for a system using PRML.

In this paper, a new method using an eye pattern is proposed to measure the signal quality for high-density recording systems. The experiment shows that the new method has a strong relation to SER of the system using PRML algorithm.

This paper discusses several issues related to adaptation and timing recovery for 2D Optical Storage. PRML detection in the form of a stripe-wise Viterbi detector is used. A 2D equalizer is applied to transform the channel response to a target response with limited span.

In this paper we introduce the Hankel transform based channel model of Two-Dimensional Optical Storage (TwoDOS) system. Based on this model, the two-dimensional (2D) minimum mean-square error (MMSE) equalizer has been derived and applied to some simple but common cases. The performance of the 2D Viterbi detector (VD) for different partial response (PR) targets in TwoDOS system is investigated. And an easy way of jointly designing the target and equalizer with suitable constraints on the target for 2D data storage systems is proposed by reducing the 2D target into its one-dimensional (1D) form. Finally, systems with different target constraints are compared and the results show that "2D monic constraint" is a reasonable target constraint for TwoDOS system.

We have shown a technique to recover real, descrambled user data from a compact disc fragment using a microscope and various signal and image processing algorithms.

A new recording mechanism for high-speed DVD-R and BD-R is proposed, and a 0.1mm cover layer with a web-coated, fingerprint-resistant, protective coating is described.

Dual polarity was observed and controlled by adjusting the composition in Al-Si binary system. Recording types of both high-to-low and low-to-high were also reported.

With the advantages of low cost, portability and compliance with ROM disc, write once disk has become the most popular storage media for computer and audio/video application. In addition, write once media, like CD-R and DVD-/+ R, are used to store permanent or nonalterable information, such as financial data transitions, legal documentation, and medical data. Several write once recording materials, such as TeO[1], TeOPd[2] and Si/Cu [3] have been proposed to realize inorganic write once media. Moreover, we propose AlSi alloy [4] to be used for recording layer of write once media. It had good recording properties in DVD system although the reflectivity is too low to be used for DVD-R disk. In this paper, we report the further results in blue laser system, such as the static and dynamic characteristics of write once media.

A single-sided double-layer recordable DVD disc with a storage capacity of 8.5 Gbyte has been developed. Backwards compatibility with the existing DVD read-only format has been achieved through the use of organic dye recording layers that have intrinsically low absorption at laser's wavelength used for recording and reading. We describe the disc technology that we have developed, present recording results for both layers, and discuss double-layer effects. We demonstrate for the first time the feasibility of a compatible double-layer recordable DVD disc.

We realized acceptable read/write performances at a track pitch of 320 nm and a bit length of 75 nm, even with an NA of 0.65 and a wavelength of 405 nm, using side-wall-annealing. In addition to this result, we suggested the possibility of a higher linear density; that is, a jitter value of less than 15% was obtained both on land and in groove at a bit length of 60 nm, which corresponds to an areal density of 34 Gbit/in².

This paper introduces the concept of producing a low cost, single layer ROM that is compatible with magnetic amplifying magneto-optical system (MAMMOS) technology.

A new version of DataPlay’s 32mm small form-factor optical disc and drive using 0.72NA, 650nm with a capacity of 750MB per disc is described.

Two different coverlayers for small form factor optical disks made of UV resin and coversheet were prepared and investigated.

We developed a new radial tilt detection method. We demonstrate that closed loop servo control worked with a high degree of accuracy on DVD±R/RW disk.

A wavelength-domain tracking scheme is a new concept for application in multiple-beam systems. Track-following is achieved by wavelength tuning. Also, a novel method of error signal extraction by low frequency modulation is proposed.

We present read-out results of a 50 GB disk with a blue laser and a NA=1.9 Solid Immersion Lens in a conventional focus and tracking actuator. Furthermore, we show a light path and a disk design that enable cover-layer incident near field recording on dual-layer disks with a capacity of 300 GB on a double-sided disk.

We have developed a high density near field optical recording disc system. We could obtain clear eye pattern for 43 GB capacity (31.0 Gbit/in2) disc.

We have succeeded in writing and reading a random pattern on a polycarbonate disc at relatively high transfer rate with a near field writing system.

An advanced PRML data recovery system is presented for a high-density recording. The system consists of three major hardware units, which are DC offset compensator, adaptive equalizer, and Viterbi detector with level adaptation scheme. The experiment based on an improved PRML scheme and FPGA hardware realization shows highly reliable performance of data detection up to 35GB recording density. The SER experiment result for 35GB shows that the detector using the proposed PRML yields a result to meet the SER limit of 4.0x10^-3 with a margin of 0.45° for tangential and 0.55° for radial tilt. And the base SER marks 7.0x10^-5 when there is no tangential and radial tilt error.

Turbo codes, a partial turbo method and a serial turbo method, were experimentally applied to a Domain Wall Displacement Detection (DWDD) disk using a red laser. An effective bit length of 68nm recording was achieved by a partial turbo method with a parity bit rate of 1/17 at a bit error rate (bER) of 4x10^-5 using a maximum a-posteriori probability (MAP) decoder, although a bit length of 80nm was the limit of the conventional partial response maximum-likelihood (PRML) method. It is presumable that the limit of the turbo decoding method for a DWDD disk depends on the number of consecutive 2-bit errors that occur with the disappearance of the 2T pattern. A max-log-MAP algorithm was introduced, instead of the usual MAP algorithm, to implement turbo codes in hardware, and an effective bit length of 69nm was achieved at a bER of 4x10^-5.

A novel timing recovery for Read Channel systems is described. This timing recovery employs a phase error calculation procedure, which extends an operating range of a phase comparator by using a feedback cross position control method.

Digital information can be encoded in the building-block sequence of macromolecules, such as RNA and single-stranded DNA. Methods of "writing" and "reading" macromolecular strands are currently available, but they are slow and expensive. In an ideal molecular data storage system, routine operations such as write, read, erase, store, and transfer must be done reliably and at high speed within an integrated chip. As a first step toward demonstrating the feasibility of this concept, we report preliminary results of DNA readout experiments conducted in miniaturized chambers that are scalable to even smaller dimensions. We show that translocation of a single-stranded DNA molecule (consisting of 50 adenosine bases followed by 100 cytosine bases) through an ion-channel yields a characteristic signal that is attributable to the 2-segment structure of the molecule. We also examine the dependence of the rate and speed of molecular translocation on the adjustable parameters of the experiment.

We report new photopolymer media for holographic data storage (HDS) at blue wavelengths (~ 405 nm), which show great promise for a practical HDS system.

We developed one dimensional data pattern hologram writer using GLV device as a spatial light modulator. The following advantages were expected: easier pixel matching, simpler signal processing, low height drive and high transfer rate. 171 angular multiplex recording holograms on a 1mm thickness polymer media, corresponding to 6.22 pixels/μm² in density were demonstrated. With a Bit Error Rate (BER) of less than 2 x 10^-4, 101 multiplexing holograms were successfully stored. Then, considerable error factors were discussed and solutions were given for higher multiplex recording.

A Novel Collinear optical setup for holographic data storage system is presented and simulated/experimental results are given. Combined with sub-page based data format, the system is simple but robust.

We propose a new error correction scheme for holographic data storage. It provides volumetrically coupled ECC blocks with iterative decoding, which can cover seriously corrupted pages, may occur due to imperfect recording media or other defects on optical devices in page based holographic memory.

We describe equalization and detection techniques that overcome both inter-page interference (IPI) and intersymbol interference (ISI) in volumetric (3D) page-oriented optical data storage (PODS) systems.

Recording and readout in two-photon absorbing Al₂O₃:C,Mg optical data storage media was investigated for crystals having different concentrations of color centers and for two orientations of the crystal optical c-axis. The writing and reading efficiency of the media was increased by taking into account the anisotropy of optical absorption and by rotating the laser light polarization vector synchronously with the disk rotation. The parameters for writing and non-destructive reading of the bits in the volume of a single crystal disk are reported.

We describe the unique characteristics of optical readout signals, and discuss the super-resolution mechanism in Platinum oxide super-RENS disks.

We report the random pattern signal characteristics of the super resolution near field structure (Super-RENS) disk in a blue laser optical system. (Laser wavelength 405 nm, numerical aperture 0.85) We introduced new structure for blue laser system, which results in 43 dB carrier to noise ratio (CNR) at the 75 nm mark length signal (which is equivalent to 50 GB capacity with 0.32 micrometer track pitch) and much better readout stability were obtained. The relatively clear eye pattern, phase locked loop (PLL) state and data to clock jitter of around 20% for a 50 GB (2T:75 nm) random pattern signal were realized.

Reflectivity variations during phase-transition between amorphous and crystalline states of a Bi-doped GeTe-Sb₂Te₃ pseudo-binary compound film is investigated with sub-nanosecond laser pulses using a pump-and-probe technique. We also use a two-laser static tester to estimate the onset time of crystallization under a 2.0-μs-pulse excitation. Experimental results indicate that the formation of a melt-quenched amorphous mark is completed in about one nanosecond, but crystalline mark formation on an as-deposited amorphous region requires several hundred nanoseconds. Simple arguments based on heat diffusion are used to explain the time scale of amorphization and the threshold for creation of a burned-out hole on the phase-change film.

We present a novel technique for the modeling of near field optical devices. The key features of this technique are the accuracy of the finite difference time domain method, the advantages of a scattered field formulation, and the direct use the complx permittivity of metals at the frequency of interest.

General design principles for surface plasmon enhanced near-field transducers are presented. Light transmission through a corrugated cylindrical aperture is studied via the BOR-FDTD method.

This paper reviews the past analytical and non-analytical approaches for the Surface Plasmons (SPs) effect, present a simple description to the widely adopted curvilinear coordinate method. Based on the concept of Fourier decomposition of any complicated grating profiles, a comprehensive analysis is given to the contribution of every order components to the overall behavior of the practical zero-order metal gratings. It successfully predicts the energy gap, resonant SPs modes, the red-shift behavior and the broadening effect of energy gap by higher order components. At the same time, it's found that within certain wavelength range of interest, only first several orders of components are needed to be taken into account to predict the behavior of the non-sinusoidal gratings. As an application, this analysis approach is extended to behavior of the triangular gratings. The limitation and possible generalization of this method are also discussed.

A quasi-vector diffraction simulation tool is introduced to simulate a fluorescent bit-wise volumetric optical data storage system. Examples and a comparison of simulation results with an analytical optical transfer function calculation are presented.

We present a method to optically store multiple information in one location by having angular momentum imparted to the scanning beam by the optical effects.

We have fabricated GaN blue VSALs (wavelength, lamda = 405 nm), and investigated their emission in terms of slope efficiency through far-field measurements. The slope efficiency of power emission from a 100 nm x 200 nm rectangular aperture as collected in the far field by an objective lens (NA = 0.65) was 1.8 ± 0.6 mW/A for the blue VSAL’s as compared with 3.6 mW/A for red VSAL's (658 nm). Both of these numbers have background transmission through the Al coating subtracted. Prior to apertures formation, slope efficiencies of 1.4 mW/A (blue) and 0.3 mW/A (red) were measured as light was transmitted through the Al coating. Finite-Difference Frequency-Domain (FDFD) simulation was used to estimate the collection efficiency of the optical measurement setup and showed the lens to collect 45% of the light emitted by the blue VSAL and 38% of the light emitted by the red. The FDFD simulations were also used to compute the efficiency of power transmission through the aperture and into the objective lens (94 ppm for blue and 65 ppm for red). Using the expected transmission coefficient for the 50 nm Al layers (220 ppm for blue and 95 ppm for red), the predicted SE values of the apertured structures are 0.6 mW/A for blue and 0.21 mW/A for red. Measured values are significantly higher, suggesting that non-idealities in aperture shape result in higher transmission efficiency, and/or that the Al coating thickness and its associated transmission efficiency have been overestimated. A thickness error of 10 nm out of 50 is enough to explain the discrepancy. Extending the analysis to 30 nm x 60 nm rectangular aperture (in cut-off for both wavelengths), the calculated output power slope efficiency for the VSAL is 7.3 microW/A for the blue and 0.06 microW/A for the red, a factor of over 100 x greater output power slope efficiency for the blue light through these smaller structures.

Phase transformations of 100nm Ge₁Sb₄Te₇ films induced by single 130fs pulse at 800nm have been investigated with time-resolved microscope. With an average fluence of 30mJ/cm², a reflective intensity increase was observed within 1ps in 100nm as-deposited Ge₁Sb₄Te₇ films after excitation by intense femtosecond pulse, which was consistent to an electronically induced non-thermal phase transformation. XRD measurement confirmed that single femtosecond pulse could induce crystalline marks in 100nm as-deposited Ge₁Sb₄Te₇ films. Our results indicated that single femtosecond pulse could trigger both crystalline and amorphous phase in 100nm Ge₁Sb₄Te₇ films. The fluence for crystallization was higher than that for amorphization.

High-power and low-noise characteristics are strongly required for blue-violet laser diodes in practical application to next generation optical disc systems. We have successfully fabricated blue-violet laser diodes meeting these requirements. These laser diodes have a ridge waveguide structure with a dielectric current blocking layer. Improving the crystal quality of the grown materials on a GaN substrate and optimizing the optical confinement in the emission layer have achieved a kink level as high as 250 mW. Optimized optical confinement is also assumed to result in a good beam profile with no fringe. In addition to this, since the threading dislocation density at the emission layer below the ridge portion is reduced to less than 10 5cm^-2, these laser diodes have been operating reliably for more than 1000 h with a light output power of 100 mW at 60 °C under pulsed operation. This light output power makes it possible to realize dual layer recording systems. We have also confirmed that these laser diodes have a noise level as low as -130 dB/Hz for a light output power of 5 mW.

We report the successful monolithic integration of a 160 mW GaInP-based laser for DVD+-RW/R/RAM and a 240 mW AlGaAs-based laser for CD-R.

We demonstrate an instantaneous phase-shift, point diffraction interferometer that achieves high accuracy and is capable of measuring a single pulse of light at NA greater than 0.8.

We propose the general idea of constructing an ultra-compact optical pickup based on photonic crystals. A few optical components necessary for various functions of an optical head are designed and analyzed.

The crystallization kinetics and recording characteristics of the Cu/a-Si bilayer recording film have been studied. Under thermal annealing, the crystallization temperature and activation energy for crystallization of a-Si with a thin Cu metal layer were reduced to about 485°C and 3.3±0.1 eV, respectively, indicating that inserting a thin Cu underlayer could effectively reduce the crystallization temperature and activation energy for crystallization of a-Si. The reaction exponent was determined to be around 1.8, corresponding to a crystallization process in which grain growth occurs with nucleation, and the nucleation rate decreases with the progress of the grain growth process. This is consistent with the hypothesis that the Cu₃Si precipitates act as the nucleation sites for the subsequent crystallization of a-Si in the Cu/a-Si bilayer recording film. Additionally, the maximum data-transfer-rates that can be achieved by the Cu/a-Si bilayer recording film at recording powers of 6, 8, and 10 mW were estimated to be about 23, 46, and 223 Mb/s, respectively.

New Ga doped GeSb based phase-change materials are investigated. These materials possess good optical contrast at short wavelengths. Crystallization temperature increasing and grain size refinement are obtained by addition of Ga. More than 50 dB CNR and 25 dB erasability are measured in disks using blue laser.

In this paper, we modeled the activation energies of GeSbTe type of phase change materials. This model is based on the analysis of the atomic bonding types in the amorphous state and the crystalline state. Both the bond numbers and bond energies were used to calculate the crystallization activation energies. The calculated crystallization activation energies of the as-deposited amorphous states match the experimental data in the literature. We also estimated the crystallization activation energies of the melt-quenched amorphous states for different GeTe-Sb₂Te₃ phase change materials. The results show that the activation energies of the melt-quenched amorphous state are 0.21~0.48 eV lower than those of the as-deposited amorphous state. This might explain the difference of the crystallization behaviors between the as-deposited and the melt-quenched amorphous states.

With the advantages of low cost, portability and compliance with ROM disk, write once media have become the most popular storage media for computer and audio/video application. Several write once recording materials, such as TeO[1], TeOPd[2], and Si/Cu [3] AlSi[4] have been proposed to realize inorganic write once media which are high to low disks. However, Toshiba and NEC have proposed a low to high rewritable media for blue laser disk.[5] Therefore, we develop a novel write once media to meet these properties. In this paper, we report the static and recording characteristics of write once media.

We have developed phase change optical media with appropriate write strategy for 1X-2X dual speed Blu-ray Disc system and for the future high speed phase change optical data storage. For recording layer, eutectic-based Ge(Sb₇₀Te₃₀)+Sb material was used and Sb/Te ratio and Ge content were optimized to obtain proper erasability and archival stability of recorded amorphous marks. The recording layer is wrapped up in GeN interface layers to obtain reasonable overwrite cyclability and higher crystallization speed. In addition, we designed appropriate write strategy so-called time-shifted multipulse(TSMP) where the starting positions of multipulse parts are shifted from reference clock. With this write strategy, the overall jitter characteristics of the disc was improved and especially we found that trailing edge jitter was improved much more than leading edge jitter. Thus feasibility of 1X-2X dual speed applicable Blu-ray Disc and its write strategy was demonstrated.

The effects of the film thickness and foreign element addition on the crystallization kinetics and optical properties of eutectic Sb₇₀Te₃₀ phase change recording film have been studied. The crystallization temperature and activation energy for crystallization of the non-doped Sb₇₀Te₃₀ recording films were decreased from 161 to 145, 144, 141, and 125°C, and from 3.0 to 2.6, 2.3, 2.0, and 1.9 eV/atom, respectively, when the thickness was increased from 15 to 20, 25, 30 and 100 nm. For the Ag-doped Sb₇₀Te₃₀ recording film of 20 nm in thickness, the crystallization temperature was found to increase from 145 to 146 and 156°C, and the activation energy was found to decrease from 2.6 to 2.5 and 2.1 eV/atom, respectively, as the concentration of Ag was increased from 0 to 3.8 and 11.8 at%, respectively. Meanwhile, the crystallization temperature and activation energy of the 20-nm-thick In-doped Sb₇₀Te₃₀ film was found to increase from 145 to 153 and 168°C, and increased from 2.6 to 2.8 and 3.4 eV/atom, respectively, as the concentration of In was increased from 0 to 1.4 and 4.8 at%.

Nitrogen doping was applied to enhance the velocity of amorphous-crystalline phase transformation. The nitrogen doping was able to produce tiny nitride precipitates uniformly distributed in the recording layer and provided numerous preferential sites for amorphous-crystalline transition. At the doping condition of N₂/Ar ratio = 3%, the recrystallization velocity of GeInSbTe phase change recording media was increased up to 1.6 times without severely damaging the signal jitter values.

We analyse two algorithms for applying DC control to a multilevel modulation data stream for optical data storage.

A new analysis of the threshold and run detectors is given and a new equalizer is designed and implemented based on this analysis.

We examined the method of setting the prediction level of PRML decoder to the signal that has an asymmetry using the computer simulation.

A new fast and accurate digital frequency detection algorithm for the optical drive system is presented. The proposed algorithm, which is based on the analysis of data histograms, improves the initialization time and the detection resolution.

We discuss the use of pulse length modulated recording of run-length-limited sequences of p-ary digits p_i ε {0, 1,... p-1}; p≥3, to effect the physical representation of digital data on a storage medium that supports three or more distinct recording levels, or types of marks. p-ary run-length-limited modulation codes that facilitate the implementation of the modulation technique are also described. We also introduce a novel error correction coding technique that enables detecting/correcting errors in the values of the non-'zero' digits in the p-ary run-length limited sequence recovered from the storage medium.

The recording property of newly developed photo-polymer for Holographic data storage (HDS) was studied. We designed two types of photo-polymers; Type-A and Type-B. Type-A is developed to be suitable for the collinear system. Type-B is designed by using conventional technology. The dependence of recording property on write energy was investigated. It was found that Type-A had higher sensitivity (0.16mJ/cm²), which indicated the capability of recording by a few pulse exposure, and lower scattering property. We also investigated recording property of shift multi-plexing.

A cylindrical multi-layered optical data storage medium based on polymer films is introduced. The usage of metal island films as tunable absorber system is proposed.

A new holographic data storage material based on narrow-band absorption is currently being developed at General Electric. Experimental characterization results of the preliminary materials are presented.

Higher packing densities in page-oriented data storage are achieved by reducing pixel pitch and inter-page spacing. We present iterative detection algorithms that combat inter-page interference.

In this paper, we develop a channel model and investigate the performance of equalization and detection schemes for the magnification error-dominated volume holographic storage channel.

The batch-thermal fixing scheme was combined into holographic disk storage, for the first time to our knowledge, yielding to a track-division thermal fixing scheme (TDTF), in order to increase the storage density and overcome the volatility of the holographic memories. As a specific batch-thermal fixing scheme, the concept of TDTF scheme was described in this paper. Three principal holographic time-constants of a photorefractive crystal for TDTF scheme were measured, based on which an appropriate exposure-time sequence was calculated and applied to record multiple holograms. The disk mount has been designed and finely manufactured, consequently, the reposition accuracy of the crystal disk can meet the requirement after the crystal experienced off-line thermal fixing. 5000 images, each contains 768×768 pixels, divided into 4 tracks , have been stored in a disk-shaped 0.03wt% Fe doped LiNbO₃ crystal using TDTF scheme. The samples of retrieved holograms showed approximately equal diffraction efficiency and good fidelity. The Experiment resulted in a high areal density of 50 bits/μm² and volume density of 10 Gbits/cm³.

This paper gives a brief introduction of the generic disc concept in the introduction section. Then a detailed description of the system architecture, software architecture, player flowchart and application software flowchart are provided in the rest of this paper.

Research on control scheme of high-density optical disc mastering by using embedded architecture with DSP as processor and CPLD as logic path was carried out.

We developed a compact mechanical mount package for Solid Immersion Lens (SIL). At 600 nm wavelength illumination, the resolution of this system is 200 nm with an effective NA of 1.5.

Near-field optical virtual probe is a kind of virtual probe based on evanescence wave interference and aperture diffraction, which has great potential in near-field optical data storage.

We present a study on application of optical waveguides as read-out units for optical recording. Simulations show that the system can resolve features well below the diffraction-limit.

We introduce a technique which enables FDTD modeling of the transmission of obliquely incident plane waves through an aperture in a film having infinite lateral extent. As an example we analyze surface plasmon enhanced light transmission through a slit in a silver film.

Particle effects to the readout signal in the in the bubble-pit configuration is studied using 2D FDTD method as a function of the readout power.

We presented new way of fitting the result of the scalar diffraction simulation to that of the FDTD method by modifying the wall angle of the media to reduce the time for the channel data simulation

The influence of the grating structures which include triangle, trapezoidal and rectangle geometries on the transmission efficiency in nano-aperture system is studied by use of 2D FDTD method.

We have developed diffractive optical element (DOE) to compensate chromatic aberration happened in aspheric lens surfaces in micro optical system. The DOE was generated with grayscale lithography using high-energy-beam-sensitive (HEBS)-glass, and we finally obtained DOEs having 4levels and 8levels through this fabrication.

Refraction of guided TE modes at thickness discontinuities in an Air/Si₃N₄/SiO₂ planar waveguide was measured by collecting light scattered into the far field from different modes. The stepped waveguides guides studied in this work are the basic refractive interfaces from which we have constructed mode index lenses. Experimental measurements of the refraction at straight step discontinuities are compared with theoretical calculations of refraction in waveguides. The coupling between incident and undesirable transmitted guided modes was found to be lower than that predicted from calculation for an ideal step. A short taper at the step may be responsible for this improvement. The maximum angle of incidence between the incoming guided mode and the normal to the interface with acceptable transmittance was found to be 50 degrees (i.e. the angle measured in the plane of the waveguide). This result is being used in other work on mode index lens design.

A full-length 50GB dual layered BD-ROM disc was producted by improvement of EBR. We got sufficient track pitch deviation and jitters through whole radius.

Nonlinear friction on a pickup head mechanism causes an objective lens shift. Detrack that causes the objective lens shift makes deteriorates read signal quality. To reduce the objective lens shift, we implement a nonlinear friction compensator in the pickup head. Experimental results confirm this compensator reduces the objective lens shift a quarter of not used.

Spin coating method for cover layer of Blu-ray Disc (BD) has been studied and a new hard coat resin including antifouling property has been developed.

We demonstrated the reading capability of a novel optical pickup which consists of a singlemode and a multimode rectangular waveguide. This system is very compact and can be extended to arrays.

A polymer focusing waveguide grating coupler(FGC) was implemented by UV nanoimprinting method. The size of this focusing grating is 1 mm X 1 mm and the total device size is 8 mm X 2 mm. We use the UV sensible polymer which is coated by spin coating method. After nanoimprinting the device, the residual thickness on the slab waveguide is about 10 nm ~ 30 nm. The spot size of this polymer FGC is 347 nm for blue laser and the coupling efficiency is 28.2%.

An easily fabricated organic holographic media is presented that is rewriteable, sensitive to 407nm light, and that exhibits high storage capacity, sensitivity, and environmental robustness.

Without applying an external magnetic field, high-density recording beyond the optical resolution limit was realized with light intensity modulation, using Domain Tail Erasing (DTE) and Domain Wall Displacement Detection (DWDD). In order to obtain a sufficiently strong bias field to perform recording with a bias layer introduced into the DTE medium, the stray field distribution during the recording process was studied by simulation. A stray field most effectively worked on the recording layer when the Curie temperature of the bias layer was designed at a certain level below the recording temperature. Furthermore, by replacing a part of the bias layer with a bias assist layer, which had a higher Curie temperature and lower coercive force, an even stronger stray field was generated. According to the simulation, non-bias DTE medium was designed, and as a result a sufficiently low jitter value and dropout rate were obtained without bias magnets at a bit length of 80 nm and a track pitch of 0.74 μm, using the same optical parameters of a current DVD.

We developed fabrication process using "all spin method" for dual layered Blu-ray Disc ROM. All of the light transmitting layer consisting of a space layer, a cover layer and a hard coat are formed by spin-coating method. Regarding the cover layer, the cycle time is less than 15 seconds and the efficiency of usage of the UV curable resin is 59%. The fabricated disc has sufficient property of thickness variation of the light transmitting layer for all disc area. The disc also has good performances of tilt characteristics including tilt transition caused by environmental sudden change due to the moisture control layer although the substrate material is conventional poly-carbonate. We confirmed the feasibility of the dual layered BD-ROM by "all spin method" and it shows the possibility of low cost BD-ROM disc.

Thermal conductivities and boundary thermal resistances of thin films having the thickness of the order of ten nanometers were measured by using the thermo-reflectance method at room temperature. A thermal simulation of HD DVD-ARW (the next-generation advanced rewritable DVD) media was carried out to clarify the effect of boundary thermal resistance at the interface of those films. The thermal conductivity of thin films greatly depends on film thickness. The result of the thermal simulation depends significantly on whether the boundary thermal resistance is considered or not. Thus it is important to consider the boundary thermal resistances and using thermal properties of thin films to perform more accurate calculation for the phase change recording media. The results of the thermal simulation also suggested that the boundary thermal resistances dominate the thermal diffusion and response of the medium.

We confirmed 64 mm-diameter magneto-optical disk systems of 4.7 Giga-byte have sufficiently wide system tolerance by domain-wall-displacement detection disks and land/groove substrates with one-side-wobbled grooves.