We report the new data reproducing scheme for high density over 40GB per layer with a commercial Blu-ray
recordable disc. bER of 10-5 and 10-4 with 42.5GB and 45GB were experimentally obtained respectively using this new
data reproducing scheme which shows the possibility of achieving 50GB with a commercial single-layer Blu-ray disc.
We also propose a new evaluation parameter which is necessary for high density.
We report the readout stability improvement results of super-resolution near field structure (Super-RENS) write-once
read-many (WORM) disk at a blue laser optical system. (Laser wavelength 405nm, numerical aperture 0.85) By using diffusion barrier structure (GeSbTe sandwiched by GeN) and high transition temperature recording material (BaTiO<sub>3</sub>), material diffusion of phase change layer and recording mark degradation were greatly improved during high power (Pr=2.0mW) readout process up to 1X10<sup>5</sup> times.
We report the error rate improvement of super-resolution near field structure (Super-RENS) write-once read-many (WORM) disk at a blue laser optical system. (Laser wavelength 405nm, numerical aperture 0.85) We used a disk of which carrier level (CL) of 75nm is improved from -26.3 dBm to -19.0 dBm. We controlled the equalization (EQ) profile characteristics and used the adaptive 5 symbol write strategy and advanced high tap partial-response maximum likelihood (PRML) technique in order to improve the bit error rate (bER) characteristics of the super-RENS random signal. As a result, we obtained bER of 10<sup>-4</sup> level with new signal processing techniques and bit error analysis process. This result shows high feasibility of super-RENS technology for practical use in the near future.
We report the random pattern signal characteristics of the super resolution near field structure (Super-RENS) disk in a blue laser optical system. (Laser wavelength 405 nm, numerical aperture 0.85) We introduced new structure for blue laser system, which results in 43 dB carrier to noise ratio (CNR) at the 75 nm mark length signal (which is equivalent to 50 GB capacity with 0.32 micrometer track pitch) and much better readout stability were obtained. The relatively clear eye pattern, phase locked loop (PLL) state and data to clock jitter of around 20% for a 50 GB (2T:75 nm) random pattern signal were realized.
For a dual layer structure, the effect of different physical geometries is studied using 0.65 and 0.85 of numerical aperture(NA), and this result gives an incitation for making a physical format for rewritable high density disc.