Two-inch-Diameter Magneto-optical Disk System with 3 GB Capacity and 24 Mbps Data Transfer Rate Using a Red Laser

Abstract

High-density recording four times that of a current DVD-RAM has been achieved by applying Domain Wall Displacement Detection (DWDD) technology using a conventional optical head which has the same wavelength of 660 nm and NA of 0.6 as the DVD head. It has been confirmed by using a sampled servo and PRML that a recording density of 15 Gbit/inch2 with a track pitch of 540 nm and bit length of 80 nm has sufficient system margin. This means that a capacity of 3 GB on a two-inch-diameter disk is now available for portable use. If applied to a digital video camera, one hour of MPEG2 video contents can be recorded at a transfer rate of 6 Mbps.

Advanced optical and magneto-optical recording techniques: a review

“…The first MO storage disks had a capacity of around 640 kB, but following the development of MSR (Magnetically-induced Super-Resolution) technology the storage capacity of commercially available systems has been increased to 1.3 GB and then up to 2.3 GB. Current research in this area is looking to apply DWDD to increase the storage capacity of these GIGAMO disks to around 3 GB by the application DWDD technology [12], and this is with a red, as opposed to a blue laser.…”

15-Gbit/in2recording on a DWDD disc using a land/groove substrate with a red laser enabled by a side-wall annealing process

“…With annealing a stripe-shaped unrecordable area is formed between land and groove, resulting in recorded marks on land and in groove that are uniformly rectangular in shape. Since an annealing process decreases the magnetic anisotropy constant Ku, the direction of the magnetization-easy axis changes from perpendicular to inplane at the annealed area [3]. 68 Proc.…”

“…They showed the interchangeability of the MD system. Birukawa et al realized 3.0 GB on a 12 inch disc with groove recording [3,4]. They used a sampled servo because the groove pitch of 540 nm was too narrow to obtain a conventional push-pull signal for tracking.…”