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The performance of a 0.6-mm-thick substrate disk was studied for tilted disk conditions. It was shown by numerical calculation that the reduction in the peak intensity of the optical spot was 0.5 dB under a disk tilt of 7 mrad when the numerical aperture (NA) of an objective lens was 0.6. The tilt angle dependence of the reading/writing performance was measured for a double-sided disk with a wavelength of 690 nm. Excellent signal quality was obtained, such as carrier-to-noise ratio of over 50 dB, erasability of more than 27 dB, crosstalk of under -27 dB, and jitter of under 30% of the window width for a tilt angle of 7 mrad.

This paper introduces a new recording method using a trilayer medium (recording layer/nonmagnetic layer/soft magnetic layer/substrate) to diminish the side written band width (ΔW). Magnetostatic coupling between the soft magnetic layer in the media and the write head poles decreases the side fringing field off the track edges. Off-track overwrite experiments revealed that the trilayer media reduced ΔW by 40%–60% compared to the monolayer medium while maintaining the effective write track width and the linear resolution.