DEMONSTRATION OF HIGH DATA DENSITY RECORDING ON DIRECT OVERWRITE MAGNETOOPTICAL DISK

We have demonstrated that the direct overwrite (DOW) Magneto-Optical (MO) disk to which we have added a GdFeCo Readout layer shows a 21% window margin for data recorded at 0.54-mu-m/bit density, twice the first generation recording density. The addition of a GdFeCo Readout layer raises the carrier level and lowers the modulation noise level several dB. This improved DOW-MO disk also shows a C/N of 53 dB at 0.75-mu-m mark length, which is several dB higher than is typical for the first generation MO disks. We have recorded data at a density of 0.54-mu-m/bit on the improved DOW-MO disk, using a write precompensation scheme in the timing of laser power. We have achieved a 21 % window margin in discrimination of the data recorded at this density. A different write precompensation scheme which enhances falling edges of laser pulses also demonstrates a remarkable improvement in discrimination of these high density recordings on the improved DOW-MO disk. Using this improved DOW-MO disk and write precompensation schemes, we have concluded that 5.25" DOW-MO disk could have 1 GB/side capacity which could be the next generation ISO standard capacity.