Kozo Taira

Magnetooptic erasable disk memory with two optical heads.

A long lifetime and high-performance MO erasable disk memory is described. It has two optical heads for the erase and write operation. Previous information is erased by the erase head; subsequently, new information is recorded by the write head, which is equivalent to an overwrite operation for a magnetic memory. The recording medium is TbCo; this has a longer lifetime than other media, which contain Fe. All components are compactly formed into a standard 13.3-cm (5.25-in.) magnetic memory drive size. This disk memory will be used as a large capacity digital memory for desktop computers or personal computers.

High-Density and High-Carrier-to-Noise-Ratio Optical Disk Mastering

A scanning tunneling microscope (STM) was used to observe the surface profile of an optical disk and to quantitatively evaluate the lithography conditions in the mastering process. A high-density and high-carrier-to-noise-ratio (C/N) optical disk was achieved using precise data concerned with the relations among the mastering process, the profile of the masters, and the readout signal.

Experimental Studies for Film Structure of TbCo Magnetooptical Disk

The authors discuss how the interference layer thicknesses affect the figure of merit (R × ¿K) of quadrilayer TbCo magneto-optic disks. Disk samples consisted of an Al reflecting layer, a frist Si3N4 interference layer (O.L.), a TbCo recording layer and a second Si3N4 interference layer (U.L.), all of which were sputtered onto transparent substrate. Varying the U.L. thickness had little effect on the reflectance R or Kerr rotation angle ¿K, but both changed significantly in response to changes in the O.L. thickness. This result could be attributed to phase differences generated within the O.L. layer.