Toshihiko Takishita

Near-Field Readout of 75 Gbyte Disc Made with Conventional Optical Disc Manufacturing Equipment

In this report, the results of the study of a 75 Gbyte (GB) disc for the solid immersion lens (SIL) system are presented. We used conventional mastering and molding equipment except for the recording process for the SIL disc. The electron beam recorder (EBR) was used as a signal recording machine for small pits. From the results of the experiments, we confirmed that conventional equipment could be used for high-density disc manufacture. The jitter value of the 75 GB disc was 9.5%.

Thermal Recording for High-Density Optical Disc Mastering

Thermal recording using a dielectric as a recording material was examined to make a high-density optical disc master. We confirmed that a pit of 53 nm length was able to be recorded with a laser of 405 nm wavelength. As a result we could make a master with a 200 gigabyte (GB) data capacity with a conventional laser beam recorder (LBR). A 100 GB disc made by the same method was able to be read with a tester equipped with a solid immersion lens (SIL) and the measured jitter value was 9.9%.

Inorganic write-once disk by complete DC sputtering process for blue laser system

We studied an inorganic write-once disk using an objective lens with a numerical aperture of 0.85 and a 405 nm blue-violet laser diode. We confirmed that the reflectivity of the disk was controllable by adjusting the nitrogen flow rate during sputtering of a Bi–Ge nitride recording layer and disk structure. The disk that had been adjusted to high reflectivity showed a large modulated amplitude. We confirmed that complete DC sputtering process is a practicable process to make inorganic recording stacks. This means that the structure of the equipment for the production of the disks will be simple and operation of it will be easy. We made the high-reflectivity disk by the DC sputtering deposition process. The reflectivity of the disk was 34%, the modulated amplitude was 60%, and the jitter was 5.8%.

Improvement of Thermal Interference for High-Density Thermal Recording Mastering

We optimized the silicon master structure with the dielectric material as the recording material of the thermal recording. We confirmed that a 48-nm-long pit was able to be recorded with a laser of 405 nm wavelength. As a result of that, we could make a 250 gigabyte (GB) data capacity master with a conventional laser beam recorder (LBR). 75 and 100 GB discs with a photopolymer cover film made by the same method were able to be read with a solid immersion lens (SIL)-equipped tester. The 75 and 100 GB disc jitter values were 6 and 10%, respectively. We also confirmed that a 37-nm-long pit could be formed with the SIL-equipped tester as the recording machine of the thermal recording.

Dual Layer Phase Change Optical Disk Using Limit Equalizer

A simple manufacturing process of multilayer recording disks has been developed to fabricate a large-capacity optical disk of more than 40 GB, using a short-wavelength laser diode and high numerical aperture (NA) objective lens. Some existing production facilities for the digital versatile discs (DVD) are applicable to this process. These disks can be utilized for long-time video recording of high-definition TV broadcasting. We have developed a dual-layer rewritable optical disk with capacity of more than 43 GB per one side of a 120 mm disk by this process. We obtained good performance of playback jitter for disks of 43 GB and 46.6 GB capacities with on-groove recording and limit equalizer at a user data transfer rate of 36 Mbps as well as good direct overwriting characteristics over 1,000 cycles.

Tin Alloy Nitride Write-Once Media for Solid Immersion Lens System

We studied a high-numerical-aperture (NA) solid immersion lens (SIL) system using tin alloy nitride write-once recording media with a protective cover layer. The jitter value of the disk that was recorded by this system was 8.5% at 100 GB capacity with a track pitch of 160 nm and a bit length of 56.25 nm. We confirmed the feasibility of the SIL-R disk using these recording media with the high-density recording SIL system.