Numerical Simulation of Read-Out Characteristics of the Planar Aperture-Mounted Head with a Minute Scatterer

KENJI TANAKA

Doctor course student at the Environmental Information Laboratory, Institute of Environmental Studies, Graduate School of Frontier Sciences, the University of Tokyo

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Introduction

The explosive increase in the amount of information available requires equipment whose density and capacity are high even by the standards of optical storage. This demand has accelerated researches on recording systems based on near-field optics, which are operative in the solid immersion lens (SIL) and aperture-mounted slider recording. These systems, however, will encounter drastically decreased detected signals in the region of the sub-sub-micron bit size, because of the use of a much smaller aperture to sustain spatial resolution. To solve this problem, in the present study we propose a novel planar aperture-mounted head with a minute metal scatterer, and we simulate its read-out characteristics through the three-dimensional finite-difference time-domain (3D-FDTD) method.

Results

Figure 1 shows the schematic diagram of the analysis model. A metal scatterer, measuring 80 x 80 x 30 nm3, is placed just at the center of a 200 x 200-nm2 planar aperture in a 100-nm-thick Ti layer. Incident light of the linearly polarized plane wave (λ=530 nm) normally illuminates the planar aperture. The recording medium, consisting of SiO2 substrate and a 40-nm-thick Ti layer having a 100-nm wide space, are placed 20 nm from the aperture.

The transmitted energy shown in Fig. 2 reveals that the signal output and the spatial resolution of the scatterer-formed head are more superior to those of the non-scatterer-formed head. Especially, the signal output is almost doubled, and full width at half maximum is improved from 150 nm to 100 nm. This result indicates that this head has the potential to realize high resolution and high signal output simultaneously, and that it realizes high recording density of over 100 Gbits/inch2.