Sub-100-nm ROM pattern readout using a triangular protruded aperture mounted optical head slider

Abstract

The continual advancement of the digital network society demands higher density and higher data transfer rates for all sorts of data storage. Optical memory based on the “near-field” principle is considered one of the most promising ones because it has no apparent physical density limit such as that due to the thermal instability encountered in magnetic recording. In light of this, we have previously demonstrated the superior readout performance of an optical head slider which is mounted on a non-circular aperture, specifically a triangular aperture having a bottom side size of 330 nm irradiated by polarized light, with this scheme indicating a clear signal response corresponding to a 70-nm-long single slit pattern. In order to fully realize the superior potential of the triangular aperture’s high spatial resolution and high signal output, it is essential to minimize aperture-to-medium spacing. In this paper, we introduce a protruded aperture mounted on a 1.5-mm-long miniaturized optical head slider whose aperture protrudes approximately 20 nm from an air-bearing surface level based on nano-step lithography technology. Utilizing a triangular aperture of 140 nm per side, a readout experiment was carefully performed at an aperture-to-medium spacing down to approximately 30 nm, corresponding to a circumferential velocity of 2.18 m/s. The influence of the incident light’s polarization direction (in relation to the bottom side of the triangular aperture) on the readout signals was evaluated by flying the aperture above a chromium patterned medium having single-space or line-and-space patterns whose line lengths ranged from 300 to 50 nm.