Mamoru Hokari

Improvement of Electron Beam Recorder for Mastering of Future Storage Media

An electron beam recorder for optical disk mastering was improved for future storage media. One improvement was related to a formatter to record constant angular velocity formats like servo patterns of hard disks. The formatter draws patterns with constant linear velocity by controlling the translation stage, the rotation stage, the beam blanker, and the high-speed deflector synchronously. The operation of the formatter was demonstrated by test drawing standard servo patterns that aligned in the radial direction and along the arc trajectory of a swing-arm actuator. Another improvement was a reduction in electron beam size. An electron beam column with a 50 kV acceleration voltage for optical disk mastering was improved by incorporating a new objective lens, the magnification of which was about 40% of the former lens. As a result, 58.5-nm pitch land-and-grooves were resolved with a linear velocity of 0.55 m/s. Furthermore a 100 kV electron beam column was developed to reduce the beam size to 10 nm or less. The width of fabricated grooves drawn by the column was about 12 nm.

High optical efficiency integrated head for use in magneto-optical disk drive

We explain the integrated magneto-optical (MO) head module that contains diffractive optical elements (DOE) and a beam-splitter (BS) with cylindrical surfaces. The optical system for servo signal detection is miniaturized by developing a multi-functional DOE. This system yields precise servo signals, and can eliminate the tracking error signal (TES) and focusing error signal (FES) independently. Power detection system is composed by using a multilevel DOE for high-speed automatic power control (APC). We suppress the distribution of the incidence angle on the BS surface, when divergent light is incident on the BS. It enables our integrated head to increase the coupling efficiency of a collimator without the deterioration of optical characteristics. When we test the head in a MO disk drive, the byte error rate (BER) of 10-6 is achieved. We confirm that this drive has the same commercial level performance for a 1.3 GB MO disk with magnetic super-resolution (MSR) technology.