We experimentally demonstrated improvement in optical disc readout signal quality by homodyne detection. We
introduced an optical phase servo system as an alternative to the phase-diversity detection scheme for stabilization of the
interference signal in homodyne detection, which resulted in further enhancement of readout signal quality.
Experimental results indicate that at least a 16-layer recordable disc can be reliably read out with a jitter of less than 8%
at a 1-mW read power by homodyne detection. The estimated amplification of signal amplitude was 13 times.
Optical signal amplification by a homodyne detection scheme is proposed and experimentally
demonstrated. We estimated that this scheme improved the signal-to-noise ratio of an 8-layer 3x
read-speed Blu-ray Disc (BD) by more than 20 dB.
To make higher density on optical disk, a new recording method- 2D recording-which can increase the track-density rather than the linear density was proposed. The performance of this method on increasing density is estimated by the simulation and confirmed by measuring the read-out signal. Consequently, it is clarified that this method can attain more than twice the areal density independently and realize the density of 2.2Gbit/in2 which is 8 times as large as that of first generation using 680 nm laser diode.
In order to gain a more reliable description of the magnetic state in the exchange-coupled films, experiments on the Hall effect in multilayer structures and computer simulations of the observed Hall effect behavior, using the distributed domain wall model, were performed. It was demonstrated that this approach can give insight into the effect of exchange interaction on the magnetization directions in TbDyFeCo/TbFeCo exchange-coupled double layer films with various extra intermediate layer.
Read/Write characteristics such as 2.2 MB/sec overwriting and 0.6 μm/bit density are obtained by magnetic field modulation and domain edge recording on a magneto-optical disk. Reliability of an interface between a floating magnetic head and a disk is investigated under artificial dusty environment.
In order to optimize the composition of recording media suitable for field modulation, the dynamic analysis of recording process was simulated. It was made clear that the recording medium whose Ms is small and Hc is high from the room temperature to Curie point is suitable for field modulation method. A high speed (2.2MB/s), large capacity (600 MB/side) overwritable 5.25"magneto-optical disk drive has been developed using magnetic field modulation by optimizing the recording media.
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