Thermal analysis of Super-Resolution Near-Field Phase Change Optical Disk

Abstract

In conventional phase-change optical recording, the disk capacity is dependent on the spot size of the laser beam, which is determined by the diffraction limit, and can only be reduced either by decreasing the wavelength of the laser or increasing the NA of the objective lens. Near-field optics has been demonstrated to record and retrieve small marks on magneto-optical media using a small aperture1). In another approach, G. Kino and S. Mansfield2) inserted a solid immersion lens (SIL) between the object lens and the surface of the surface-incident disk. However, near-field optics using the SIL has encountered many difficulties in its feasibility and implementation. This is due to the narrow space of less than 100nm between the near-field probe and the recording medium. To overcome this problem, a dynamic aperture formed by melting the mask layer in the Super-resolution near-field disk (Super-RENS disk)3), is used as a near-field probe. Using the Super-RENS technology, high densities beyond the diffraction limit of the laser have been demonstrated. In this structure, the distance of the aperture and recording layer is fixed at a constant height, eliminating the problem of maintain this distance as in the case of using the SIL. Recently two new structures of the Super-RENS disk were proposed to solve the problem of poor thermal stability4). The new structures with a thermal shield layer but at a different position in the structure, are proposed and named new structure 1 and 2, shown in Fig 1 (b) and (c). The thermal shield layer has been found to enhance the thermal stability of the Super-RENS disk. Hence it is very important to study the effect of the position of the thermal shield layer on thermal stability. In this paper, the conventional and new structures of the Super-RENS disks were analyzed and their performance compared.