Pulsed Laser's Influence on the Readout Characteristics of a CAD Type MSR Disk

Abstract

We developed a high-density magnet-optical disk system named “iD (intelligent or image Disk) PHOTO for use in mobile storage devices such as digital still cameras. This system achieved a recording density as high as 4.6 Gb/in2 by adopting technologies, such as CAD type MSR (Center Aperture Detection type Magnetically induced Super Resolution) readout method, LP-MFM (Laser Pumped Magnetic Field Modulation) recording method, etc. It was reported that using the pulsed laser instead of the continuous laser in the readout process improved the carrier level of the CAD type MSR media at the shorter mark length. The purpose of this study is to clarify the effect of the laser pumped readout method on the characteristics of the iD PHOTO system. Using the laser pumped readout method, we can get larger readout margin than the continuous irradiation. At lower duty ratio, the readout margin is larger, but the erased ratio is lower than that of higher duty ratio. At the optimum bottom power there is a large readout margin and a high erased ratio. The erased ratio at 1.2 mW of bottom power was up to 26 % higher than that of continuous irradiation. The influence of the laser pumped readout method on the characteristics of the erased ratio makes it a useful technique for the CAD type MSR disk.