Ultrahigh Density Magneto-optic Recording Technology

Magneto-optic recording technology emerged into the marketplace in 1989 and by 1991 had total sales of $261 million. Sales in excess of $1 billion are projected in the near future. The areal density of the initial products was about 200 h4bits/inz, but second generation products with storage densities of factor of two higher are now emerging. Much higher areal densities can be expected in the future. In this paper, the evolution of the technology toward a storage density of 10 Gbit/inz will be considered. It will be argued that, by using 400 nm wavelength light from new laser sources now under development, higher numerical aperature objective lenses, improved position error signal generation techniques, advanced modulation and error correction codes and zone bit recording, the areal storage density of magneto-optic drives will continue to increase and likely keep pace with mangetic disk technology. For this to occur, new magneto-optic recording materials are required. Both garnets and Co/Pt multilayers have potential for meeting the requirements. Both have large magneto-optic effects in the blue wavelength spectrum. It is desired to reduce the media noise level in both materials, but recent results indicate this problem will likely be solved. Because magneto-optical heads are today made of discrete optical components, they are massive and large in comparison to magnetic recording heads. This has so far prevented rapid seek times and putting more than one disk on a spindle. Advances in head technology, involving fiber optics and electro-optic beam deflection could provide rapid track-to-track seeks and more compact heads. Furthermore, the recent demonstration of 45 Gbit/in2 recording density by using near-field techniques suggests that magnetooptic drives could eventually compete directly with Winchester disk drives. This talk will review the status of magneto-optic recording technology in light of the above developments.