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.
Optical disk system using blue-violet laser
Many technologies for the next DVD generation using a blue-violet laser have been developed. This disk system will be applied for audio-visual application and computer peripheral application, like DVD-RAM. In this system three items, large capacity, high data-transfer-rate and reliability, are equally important and their targets have been set. To go toward these targets, the following technologies corresponding to technical fields such as media, optical head, servo-mechanism, read/write channel, signal processing and so on have been developed. Additionally, the basic subjects crossing over these technical fields to solve new problems that have arisen from this generation and have been neglected before were studied.
Refinement of crystal structure parameters using convergent‐beam electron diffraction: the low‐temperature phase of SrTiO3
The method to refine crystal structure parameters (atom positions and Debye–Waller factors) using convergent-beam electron diffraction (CBED), which is applicable to crystal structure analysis of a small specimen area down to a few nm in diameter, is studied. The line profiles of higher-order Laue-zone reflections are recorded using imaging plates. Theoretical intensities are calculated based on the dynamical theory of electron diffraction with the aid of the generalized Bethe approximation to shorten calculation time. The structural parameters are determined by fitting the experimental profiles with the theoretical ones using a nonlinear least-squares method. The present method has been applied to the low-temperature phase of SrTiO3. The structural parameter or the rotation angle of the oxygen octahedron has been determined to be \varphi = 1.12 (4)°, which shows good agreement with that obtained from electron spin resonance experiments.