Read-out characteristics of a triangular aperture mounted optical head slider applied to a polarized light: spatial resolution in the circumferential direction

Abstract

Optical memory based on the “near-field” principle is considered one of the most promising technological breakthroughs 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 demonstrated the superior readout performance of an optical head slider mounted on a triangular aperture with a typical side size of 140 nm irradiated by polarized light. With this scheme, we have indicated a clear signal response corresponding to a 150-nm line-and-space (L/S) pattern. In this paper, we introduce a protruded aperture mounted on a 1.5-mm-long miniaturized optical head slider whose aperture protrudes approximately 25 nm from an air-bearing surface. Utilizing a triangular aperture irradiating polarized violet laser light, we performed a readout experiment at an aperture-to-medium spacing down to approximately 29 nm. A clear readout signal was obtained corresponding to the pattern down to 100-nm line width, in spite of the usage of a fairly large side size of 330 nm. We also evaluated the influence of the incident light’s polarization direction on the readout signals while changing the line width of the L/S patterns from 300 to 100 nm. A polarization direction perpendicular to the bottom side of the aperture provided both higher spatial resolution and better signal contrast. We also observed a “spike phenomenon” when the aperture passed through the boundaries between the metal portion and the space (or line-and-space) portion. We believe this phenomenon is the cause of the enhancement or suppression of specific L/S pattern or period signals.