0.04 μm domain expansion readout for the magnetic amplifiying magneto optical system

Read/write characteristics of the magnetic amplifying magneto optical system (MAMMOS) with alternative readout fields such as carrier to noise ratio (C/N), eye pattern, jitter and bit error rate (BER), are investigated with a 640 nm wavelength laser diode and 0.55 numerical aperture of the objective lens. The C/N value of 0.12 mu m is 50 dB and is independent of the mark length. A very clear eye pattern was observed. The results show that the jitter value is less than 3% compared with the window width and it is only dependent on the switching speed of the readout field. The error rate is improved by using a thin recording layer of 50 nm in thickness. The minimum domain length which yields a BER of less than 1 x 10(-4) is 0.045 mu m (45 nm); the minimum space length is 0.10 mu m (100 nm). These results are confirmed at a track pitch of about 0.40 mu m. By using a digital versatile disk (DVD) pickup, the areal density can be estimated to be about 23 Gbit/in(2) with the user data capacity of 30 GB/120 mm phi. By using a 400 nm blue laser diode, these values are estimated as 59 Gbit/in(2) and 77 GB/120 mm phi.