Design of DWDD disk with groove recording for high density and wide recording power tolerance

We previously reported the performance of high density magneto-optical (MO) recording with NA 0.85 and blue laser using land/groove substrate (T. Miki et al, Proc. SPIE vol. 4342, pp. 220-227, 2002). In that report, we confirmed that the groove shape of the substrate improves the recording power tolerance using land/groove substrate. DWDD (domain wall displacement detection) MO (T. Shiratori et al, J. Magn. Soc. Jpn., vol. 22, supp. no. S2, pp. 47-50, 1988) is the most useful medium for achieving high linear density recording without using higher NA objective lenses. Land/groove recording using DWDD has already been reported (S. Kai et al, Jpn. J. Appl. Phys. vol. 38, pp. 1768-1773, 1999; G. Fujita et al, Tech. Dig. ISOM '01, pp. 84-85, 2001; T. Sakamoto et al, Tech. Dig. ODS 2001, pp. 73-75, 2001). Securing a wide recording power tolerance is very important to realize a high density optical storage system. From this point of view, we investigated DWDD MO with groove recording using blue laser and NA 0.60 optics. We optimized DWDD media for groove recording and improved the groove shape of the substrate to obtain wider recording power tolerance at higher linear density.