Kazutoshi Kitano

Organic Dye 25 GB Write-Once Disk with In-Groove Structure

We have developed a new write-once disk technology, which is applicable to the Blu-ray disc system. An organic dye was adopted for the recording layer, which was optimized for the recording of the laser diode wavelength of 405 nm. We adopted a concave in-groove for the recording tracks to avoid thermal interference with adjacent recording tracks due to undesired and uneven dye pooling between adjacent tracks, considering the advantage of fabrication by spin-coating. We optimized the in-groove structure for low-to-high modulated recording. A sample disk, which was made by the conventional spin-coat process, showed good recording and readout characteristics with remarkably low cross-talk and cross-writing.

Layer Stack Design of High Density Read-Only-Memory Discs for Near-Field Systems using a Solid Immersion Lens

For high numerical aperture (NA) near-field systems using a solid immersion lens, layer stack types of first-surface read-only-memory (ROM) discs have been investigated. Complicated interactions of high-NA incident and diffracted waves with surface waves occur in multilayer-stacked subwavelength structures on the discs. Therefore, vector diffraction simulation in consideration of these effects is indispensable for the optimization of the disc structures. We used rigorous coupled wave analysis to numerically calculate readout signals from the discs. On the basis of the simulation results, we actually fabricated high-density ROM media. Consequently, a significantly low jitter of 6.8% was obtained for 100 Gbyte ROM media with a designed structure in an NA 2.0 system.