Jun Sumioka

A New Data Detection Method for 35 Gbit/inch2 Multilevel Recording Using a Blue Laser and 0.85 Numerical Aperture Optics

In this study, a commercial Blu-ray disc was used for multilevel recording. The goal is to make its present capacity 2 times larger and data transfer rate 2 times faster. This technology is a promising candidate for improving extending the standard of the Blu-ray disc. To achieve this specification corresponding to an areal density of 36 Gbit/in.2, the bit length is reduced to 56 nm. The features of technology for 36 Gbit/in.2 are as follows: First, eight-level recording is adopted. Second, a new detection method named cell boundary data detection (CBDD) is developed to overcome severe intersymbol interference (ISI) from outer cells at a small cell length. Finally, we use the same optical pickup as that of the Blu-ray disc for doubling areal density. CBDD utilizes data sampled at the cell boundary, which is almost free of the influence of ISI without an equalizer. In addition, the popular error correction code of Bose–Chaudhuri–Hocquenghem (BCH) is applied to the part of the least-significant bit (LSB). As a result, CBDD with the BCH code achieved a bER of 1 ×10-5 at the effective bit length of 57.6 nm, which indicates an areal density of 35 Gbit/in.2 by computer simulation. Moreover, we experimentally obtained a bER of less than 1 ×10-5 using CBDD with the BCH code at a cell length of 200 nm.

An Advanced Data Detection Method for 34.6-Gbit/in2 Multilevel Recording using a Blue Laser and NA0.85 Optics

In this study, a commercial BD (Blu-ray disc) and BD optics (blue laser and NA0.85) were used for multilevel recording. The goal is to double both the present capacity and data transfer rate. To achieve this, it is necessary to overcome severe inter-symbol interference (ISI) from outer cells at a small cell length. In order to suppress ISI, we have developed an advanced data detection method that uses CBDD (Cell Boundary Data Detection) and TCM (Trellis-Coded-Modulation), and have achieved an areal density of 34.6-Gbit/in2 multilevel recording.

A DWDD disc of 27-Gbit/in2 land-groove recording using a blue laser and side-wall-annealing technique

We realized acceptable read/write performances at a track pitch of 320 nm and a bit length of 75 nm, even with an NA of 0.65 and a wavelength of 405 nm, using side-wall-annealing. In addition to this result, we suggested the possibility of a higher linear density; that is, a jitter value of less than 15% was obtained both on land and in groove at a bit length of 60 nm, which corresponds to an areal density of 34 Gbit/in2.