Makoto Horiyama

Three-Dimensional Microstructures Created by Laser Microfabrication Technology

Three-dimensional microstructures with aspect ratios larger than 20 and a solidified wall with a thickness down to 2.0 µm have been fabricated by the one-photon absorption photopolymerization technique. Lateral and longitudinal spatial resolutions in a single-line scanning process of as high as 1.0 µm and 0.3 µm, respectively, are reproducible. An experimental system consisting of a common picosecond pulsed laser and an optical microscope makes laser microfabrication easy to realize, implying a broad application potential.

New Tracking Servomechanism Using Phase-Shift Differential Push-Pull Method for Recordable Optical Disks

We have improved the phase-shift differential push-pull (PS-DPP) tracking method with a multidivision phase-shift grating, which is applicable to various optical disks with different track pitches and does not require the accurate alignment of the three-spot position on a disk. In this paper we presented the properties of this method in recordable optical disks such as phase-change or dye media in which reflectivity greatly changes after recording. In particular, we found the cause of a radial tracking error signal offset occurring at the boundary between recorded and unrecorded tracks. To resolve this issue, we proposed two solutions: one is the optimum calculation procedure for the PS-DPP signal, and another is a newly designed phase-shift grating for recordable disks. We demonstrated the offset cancellation effect of this improved PS-DPP method using a new hologram laser unit for various types of digital versatile discs (DVDs) and showed its applicability to the Blu-ray Disc (BD).

Spherical aberration error detection for blu-ray disc optical pickups

For a high-numerical-aperture (NA) optical pickup system, the spherical aberration (SA) caused by cover layer thickness error should be corrected. We detected the SA error signal using a newly designed hologram optical element (HOE). The HOE has both sufficient signal sensitivity and constant signal level independent of objective lens shift. In addition, we fabricated on SA servo for a dual-layer Blu-ray disc.