Simulations of heat generation and conduction on a land/groove disc
We applied the finite-difference time-domain (FDTD) method to an optical disc to estimate the energy absorption inside a multi-layered disc with land-and-groove structure. The FDTD method was developed to measure the electromagnetic fields generated by diffraction in a near-field. Afterwards we analyzed the heat conduction. We found that temperature transition depended not only on conductivity but on the initial distribution of the heat and on disc geometry.
Design of a Near-Field Probe for Optical Recording Using a 3-Dimensional Finite Difference Time Domain Method
Tapered dielectric near-field probes are designed for optical recording by means of a 3-Dimensional finite difference time domain (FDTD) method. Probe fabrication is attempted with a double-exposure holographic technique.
Land and Groove Recording for High Track Density on Phase-Change Optical Disks
We have proposed a high-track-density optical recording method, which records signals on both the land area and groove area. From a computer simulation based on the scalar diffraction theory, we found that crosstalk between recording tracks depends on the groove depth, and is most reduced at the groove depth of 80 nm∼90 nm for a laser wavelength of 780 nm, a numerical aperture of 0.55 and a track pitch of 0.8 µm. Applying this method to a phase-change optical disk, we experimentally confirmed that crosstalk depends on the groove depth and obtained a crosstalk level of less than -32 dB for a groove depth of 64 nm to 78 nm and 0.9 µm length marks. In order to prove that this recording method can be used for rewritable media, we also measured change of carrier-to-noise ratio (CNR) when signals were repeatedly recorded on an adjacent track. The reduction of CNR after 1000 repetitions of writing was less than 2 dB for a linear velocity of 5 m/s.