KEYWORDS: Near field, Modulation, Near field optics, Signal processing, Photoresist processing, Reflectivity, Scanning electron microscopy, Objectives, Silver, Optical storage
This article will describe a series of experiments we conducted for the purpose of pursuing the resolution limit of the PTM process. Disc samples with different track pitches and different linear densities were prepared through the PTM process. The signal properties of these discs were analyzed with the assistance of a near field readout system. The jitter value was 5.6% at the linear density of 70nm/bit and 0.16μm track pitch, which corresponded to 80GB per 12cm diameter disc. Even at a recording density corresponding to a capacity of 100GB we observed jitter values less than 10%.
KEYWORDS: Optical recording, Signal processing, Deep ultraviolet, Objectives, Tolerancing, Indium gallium nitride, Signal to noise ratio, Amplifiers, Semiconductor lasers
The possibility of high-density groove-only recording was investigated by using a high-numerical-aperture lens unit and an InGaN semiconductor laser. Wobbled grooves of 20 nm in depth were formed through a deep-UV disk mastering process and replicated by injection molding onto a polycarbonate disk substrate. This shallow wobbled groove structure improves a signal-to-noise ratio (SNR) and also enables an address in pre-grooves (ADIP). In the experiment, signals were recorded either in or on the grooves, and the achievable areal recording density was carefully examined in each case, comparing with a previous land-and-groove disk configuration. The authors' results indicate that the signal recording on the grooves, which correspond to the structured area located closer to the objective lens, brings higher track density than that in the grooves. A bit size of 120 X 320 nm, an areal density of 16.8 Gbit/in2, was verified at the data transfer rate of 35 Mbps on a phase-change disk of SbTe-based eutectic composition. This bit density can realize a storage capacity of 23.3 GB on a f 120 mm disk. Further investigation on higher areal density was also examined with an additional signal processing.
KEYWORDS: Signal detection, Optical discs, Digital video discs, Modulation, Signal processing, Quadrature amplitude modulation, Digital modulation, Data conversion, Data storage, Eye
We propose a method to record a multilevel signal onto an optical read only memory disc. In this method, we use the signal processing to generate the multilevel recording signal, which satisfies zero-intersymbol interference condition and zero-direct current condition. The resultant multilevel signal is emboss recorded as position displacement of groove walls. To playback a disc, the push- pull detection and the adaptive equalizer is used. Experimental disc of 0.6 micron trackpitch and a 0.28 micron/bit of density is made. When a DVD equivalent optical pickup is used to playback this disc, we confirm the error rate of 3 X 10-4 and a clear 2D eye pattern of 16 levels.
Land/groove recording in an MO system was demonstrated using MFM recording technology and a 690 nm wavelength diode laser. The CNR of 55 dB and cross-talk of about -35 dB were obtained at a 1.88 micrometers recorded mark length and a 0.7 micrometers yielded a 0.35 micrometers bit length and a 0.7 micrometers track pitch were 8.1% on land and 8.7% on groove. The disk tilt margins were radially +/- 0.42 deg and tangentially +/- 0.45 deg when reading out on land, and +/- 0.40 deg and +/- 0.44 deg on the groove. The recording power margins were estimated to be +/- 8.0% on land and +/- 9.0% on groove considering over-writability and cross-write characteristics.
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