Advances in magneto-optical super-resolution for very high density MO recording

Abstract
Large capacity is a strong requirement for the next generation of magneto-optical disks in order to manage huge amount of data such as digital images. We reported that superresolution can be realized by using an exchange-coupled multilayer disk in 199 1. This novel technology is called Magnetically Induced Super Resolution (MSR) and it more than doubles the readout resolution limit of the conventional optical disk system without shortening the laser wavelength or increasing the numerical aperture (NA) of the optical lens 1),2)• The essence of MSR is that a part of the focused light spot used for readout is masked, so the effective aperture becomes much narrower than that for conventional detection. Figure 1 shows two types of detection, front aperture detection (FAD) and rear aperture detection (BAD). Since dc light is irradiated onto moving media, the medium at the rear of the light spot is much hotter. In FAD, the light spot area overlapped by the heated area is optically masked, so the signal is detected from the crescent-shaped aperture. In BAD, the crescent-shaped area is masked because the signal is erased by the initializing field prior to the readout. We would like to review some of our investigations and clarify what is important to realize an MSR system.

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