Takao Hirahara

Magnetic duplication for precise servo writing on magnetic disks

A servo pattern of a 20 Gbit/in/sup 2/ level was directly duplicated on hard disks by using a magnetic duplication method, and the accuracy of the signal and the following performance on the duplicated servo pattern were evaluated. The phase servo pattern was composed of straight lines and was lithographically formed on a mastering disk. The period accuracy of the readback signal was very high. The repeatable position error for adjacent tracks in a prototype drive was measured, and the difference between two adjacent RPE trajectories was sufficiently small. The magnetic duplication method showed the possibility of precise servo-track writing for high-density hard disk drives.

Automated optical passive alignment technique for PLC modules

We have developed an automated optical passive alignment technique for planar lightwave circuit (PLC) modules. Our technique is based on aligning a laser diode (LD) on a PLC module, and can be used to create an optical network unit. The PLC module we propose consists of a LD and a photodiode, which are mounted on the surface of the PLC platform without a lens. Because these elements send light directly to the waveguide on the PLC platform and receive light from the waveguide, a precise alignment technique is required. We therefore developed the mirror image alignment method in order to automatically align the LD on the PLC with extreme accuracy. The method is effective regardless of the position of the LD and the thickness of the solder. The mirror image method uses the markers on the PLC and their images, which are reflected on the front wall of the LD. The achieved accuracy for positioning was within 1 micron in the lateral direction and within 0.5 degrees in the rotational direction. These systems are now being used at a Fujitsu factory.