Super-Resolution Optical Disc with Radial Density Increased by Narrowed Track Pitch Corresponding to Diffraction Limit

Abstract

In–Sb-based super-resolution near-field structure read-only-memory discs with radial density increased by introducing a narrow track pitch corresponding to the diffraction limit of an optical system were developed. Using an optical system with a laser diode with a wavelength of 405 nm and an objective lens with a numerical aperture of 0.85, we confirmed that differential phase detection (DPD) could detect track errors from disc samples recorded random data including a minimum pit length of 75 nm in a 240 nm track period. It has higher capability of track error detection than push–pull detection at a narrowed track pitch. Moreover, bit error rates satisfying the criterion of 3.0×10-4 were experimentally obtained for 66.7-GB-capacity disc samples with a 240 nm track pitch through signal processing with the partial response maximum likelihood of the (1,2,2,1)-type, by applying DPD to tracking servo control. The feasibility of increasing the track density of the Blu-ray DiscTM physical format by 1.33 times was indicated.

High-density channel model and detection method for signal readout from super-resolution near-field structure discs

“…[16][17][18] A super-resolution near-field structure (super-RENS) ROM disc with the mask layer of InSb is also proposed, in which a partial response maximum likelihood (PRML) method selecting either PRML (1221) or PRML (12221) is used. 19,20) When the laser beam heats the mask layer, the refractive index of the layer changes and optical transmission increases within a small area, thereby allowing the reproduction of the recording marks below the diffraction limit. [21][22][23][24] Consequently, waveforms read from super-RENS discs have a complex channel property that includes normal and differential readout components caused by the super-RENS effect.…”

A high transmittance optical recording material with long-term reliability for super-multilayer discs

“…[1][2][3][4][5] As a means of increasing the data storage capacity, several technologies have been reported, such as holographic technology, 6,7) near-field technology, 8,9) multilayer technology, [10][11][12][13][14][15][16] and others. [17][18][19][20][21][22][23][24] Among these, multilayer recording technology is a promising approach because it can utilize most technologies of the Blu-ray Disc™ system that is already in use as a commercial technology. 25) Because many recording layers are stacked in a supermultilayer disc, the intensities of the reading and recording lasers are attenuated at the deeper layers.…”

The physical understanding on dynamic readout/detection of super-resolution pits with nonlinear reverse saturation absorption thin films

“…In the super-resolution read-only optical disc, the minimum pit size (2T signal) is 75 nm, which is smaller than the resolution limit of a Blu-ray DVD player. This playback is an important advance in driving mass-scale application of nonlinear thin film super-resolution techniques [9][10][11].…”