Fujitsu currently produce a number of Magneto Optical based storage product offering up to 640MB storage per disk (see M2513A), In fact Fujitsu produced the industry's first 1" high 3.5" drive device. Magneto Optical units as their name suggests work by combining a magnetic head with a laser reader similar to those used in CD-ROM drives.
Writing to the disk requires the use of both laser beam and magnetic head, while reading requires only the laser beam. The latest generation of Fujitsu MO's are capable of storing 640MB per 3.5" disk whilst still being able to read & write to the earlier 230MB format disks and use the original 128MB disks in read only mode.
The Fujitsu MO drive is currently fitted with a SCSI interface, ATA devices will be available shortly.
To write a single bit of information to an MO disk requires that the laser heats the location to the Curie temperature, and at that moment the magnetic head applies the required polarity to store either a '0' or a '1'. The laser is then switched off causing the temperature to drop and locking that data bit into the disk.
The Laser beam is used to read the data, the laser beam is deflected differently depending on whether a '0' or a '1' has previously stored at that location. The magnetic head performs no function during the Read cycle.
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