Super-resolution Disk Research Articles

Spot Shape on Super-Resolution Optical Disks with a Photon-Mode Mask Layer

The spot shape on super-resolution optical disks with a photon-mode mask layer was theoretically analyzed. The spot shape was found to depend on the lifetime of the bleached state of the dyes, the light power, and the disk rotation speed. When the lifetime is short, the super-resolution spot shape is not produced at high disk speeds. On the other hand, a dye mask layer with long lifetime, such as a photochromic mask, can produce a sharp spot shape in the higher disk speed region, and therefore is suitable for obtaining a super-resolution disk with a high data transfer rate.

Short-marks recording characteristics of laser-pumped magnetic-field-modulation recording in a narrow track pitch and on magnetically induced superresolution disks

We evaluate laser-pumped magnetic-field-modulation (LP-MFM), continuous laser-irradiated magnetic-field-modulation, andlight-intensity-modulation recording in magneto-optical disks, usingtemperature calculations and experiments. LP-MFM is useful forrecording short marks: One can record magnetic domains as small as 0.15-mum marks with LP-MFM by using a spin-polarized scanningelectron microscope. LP-MFM is also useful for reducing the trackpitch. Experiments showed that no cross write occurred at a 0.6-mum track pitch, and calculation showed that the heatdistribution is narrow. We confirmed the advantages of LP-MFM forrecording magnetically induced superresolution disks by investigatingthe difference in the shapes of the recorded domains.

Evaluation of a 120 mm Sized Magneto optical Disk System of Over 6 GB Capacity

We have studied the feasibility of the 120-mm-sized magneto optical disk system which achieves 6-GB user capacity using an optical pickup with a 640-nm wavelength laser and a 0.6-numerical aperture of the objective lens. We have used three technologies: a laser-pulsed magnetic-field modulation recording, a center-aperture-detection type of magnetically-induced super resolution disk with a 0.6-mm-thick single substrate and partial response equalization with maximum likelihood detection. We have evaluated the system-margins of write power, radial tilt, tracking and focusing offset and have confirmed the feasibility of the linear bit density of 0.235 µm/bit in 0.6-µm track pitches.

The Influence of the Rear Mask on Copying Recorded Marks for Magnetically Induced Superresolution Disks

Magnetically induced superresolution (MSR) disks by double masked rear aperture detection (D-RAD) sometimes show direct transition from the initialized state to the D-RAD state in the readout power curves. Peak and trough levels of read signals for these MSR disks were measured and the states of the aperture and the rear mask during the readout were clarified. When the read field is in the erase direction, the aperture opens simultaneously with the collapse of the mark in the rear mask. When the read field is in the write direction, copying a mark from the recording layer to the readout layer starts as the mark in the recording layer overlaps the rear mask and the successive wall displacement copies the mark. The MSR with the latter mechanism was found to be very effective for eliminating crosstalk.

Super-Resolution Disk with a Photochromic Mask Layer

Super-resolution readout for read-only optical disks was demonstrated using a photochromic mask layer. Nonlinear transmittance change, which is desirable for effective super-resolution readout, was achieved using a the photochromic mask layer with an optical density of 0.5. The photochromic super-resolution method is expected to increase the recording density of not only read-only disks, but also magneto-optical and phase change disks.

LAND/GROOVE RECORDING SCHEME ON MSR MEDIA

Land/groove recording properties on a magnetically induced super-resolution (MSR) disk has been investigated. We prepared an exchange coupled type of MSR disk with double magnetic layers and examined the read/write characterisitics for various track pitches with magnetic field modulation recording. As the results, a track pitch of 0.65 μm was available for practical use from the point of view on crosstalk and crosswrite properties. We have also developed a new groove format in order to obtain address information on both lands and grooves.

High density recording on magnetically induced super resolution disk with magnetic field modulation and pulsed laser irradiation

The magnetically induced super resolution disk with an in-plane magnetized layer (CAD-MSR) is one of the most useful candidates for high density recording because of its simple structure and no initializing fields. This paper describes an evaluation of a CAD-MSR disk using magnetic field modulation with a pulsed laser, which is also useful for high density recording. We obtained a jitter of less than 10% at a bit density of 0.3 /spl mu/m/bit (2 T=0.4 /spl mu/m in (1,7) RLL code). The real density corresponds to an unformatted capacity of more than 5 Gbytes on a /spl phi/ 120 mm disk.

New Disc Format for Land/Groove Recording on Magnetically Induced Super-Resolution Disc

We developed a new disc format for land/groove recording. The new disc had grooves wobbled on one side to obtain address information. We examined characteristics of signals reproduced from the wobbled grooves and a suitable groove shape for a double-layered magnetically induced super-resolution disc. By the use of the new disc format, good signal quality of address information is obtained on both lands and grooves. At a groove shape with 40 nm depth and 0.7 µm track pitch, a CNR of 47 dB and a crosstalk of -32 dB were obtained at the recorded mark length of 0.55 µm in magnetic field modulation recording.

High density recording with a super resolution magneto-optical disk using magnetic field modulation method

We have improved the recording magnetic field sensitivity of a magnetic super resolution (MSR) disk consisting of double magnetic layers and examined the magnetic field modulation recording properties. An areal density of 2.2 Gbit/in 2 was obtained with a currently available condition. The experimental optical pickup system had a 680 nm wavelength laser diode and an objective lens of a 0.55 numerical aperture. The MSR disk had 0.7μm-width lands and grooves. The crosstalk values between the land and its adjacent grooves were less than −28 dB. The areal density in the improved MSR disk was accomplished by recording in both lands and grooves and using mark edge recording with a (1,7) run-length-limited coding. Also, if a signaling technique called ‘PRML’ is used, an areal density of 3.1 Gbit/in 2 could be realized.

New magnetically induced super resolution disk by using exchange-coupled magnetic layers

Readout process of a new type of magnetically induced super resolution (MSR) disk was analyzed by calculating a domain shape in exchange-coupled ferrimagnetic layers. Analysis revealed that a suitable wall energy density at an interface between the layers existed for improving readout characteristics. This result obtained from calculation was confirmed by experiments. An areal recording density of 2.4 Gb/in/sup 2/ was achieved by using an 830 nm wavelength laser.

Magnetic super-resolution

Magnetically induced super-resolution (MSR) disks have been proposed to overcome the diffraction limit. This paper reports an MSR disk which has exchange-coupled magnetic double layers. An in-plane magnetization film is used as a readout layer in the magnetic double layers. The MSR disk can be overwritten by a magnetic field modulation recording method. An areal density of 2.2 Gbit/in/sup 2/ was obtained with a currently available optical head having a 680 nm wavelength laser. Besides, the disk had high recorded-data-stability in continuous readout of 5/spl times/10/sup 5/ revolutions with a laser power of 2.5 mW, and it also kept a high signal quality after a continuous erasing test of 2/spl times/10/sup 5/ revolutions with a recording laser power of 6.5 mW.

Copying Characteristics of the Magnetically Induced Superresolution Disk

Copying characteristics of recorded domains from the recording layer to the readout layer were studied for the magnetically induced superresolution disk. It was found that the larger the difference of the wall energy between the switching layer and the readout layer was, the better copying characteristics were. The copying field of a domain tended to be much less than that without or outside of a domain. To explain this behavior, it was proposed that the interface wall within a domain sinks into the recording layer in comparison with the one without or outside of a domain.