Optical recording at 2.4 gbit/in² using a frequency doubled diode laser

Optical recording at 2.4 Gbit/in2 has been demonstrated at both 488 nm (argon-ion laser) and at 429 nm (doubled diode laser) using TbFeCo and CoPt multilayers on flat glass media with a soft sampled servo tracking system. The data was written using pulse width modulation (PWM), 2/3 (l, 7) run length limited (RLL) encoding, and detection accomplished using a dual clock channel. Edge shifts of 3.5% of the timing window and jitters of 7% of the timing window were observed. At a data rate of 2 MBytes/s and with data written on adjacent tracks, a bit error rate of 10-5 with noise margins of 10 dB and 8.5 dB were measured at 488 nm and 429 nm, respectively. © 1993 The Japan Society of Applied Physics.