Triangular Aperture as Near-Field Element for High-Density Storage

Masakazu HIRATA
Manabu OUMI
Koichi SHIBATA
Kunio NAKAJIMA
Toshifumi OHKUBO

Publication
IEICE TRANSACTIONS on Electronics   Vol.E90-C    No.1    pp.102-109
Publication Date: 2007/01/01
Online ISSN: 1745-1353
DOI: 10.1093/ietele/e90-c.1.102
Print ISSN: 0916-8516
Type of Manuscript: Special Section PAPER (Special Section on Microoptomechatronics)
Category: Plasmonics and Nanophotonics
Keyword: 
near-field,  triangular aperture,  contact slider,  storage,  

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Summary: 
Near-field optics is one of super-resolution techniques for future data storage system. We have already proposed a near-field optical flying head with a circular aperture. For realizing higher performance aperture, we developed a triangular one that has been experimentally evaluated with a scanning near-field optical microscope probe. By controlling the polarization of the incident light to the aperture, we could obtain a 100 nm resolution with a 190 nm-wide aperture. We also demonstrate the readout performance of this novel aperture mounted on a near-field head by introducing polarization control. To scan over a medium surface under a small-spacing condition, we fabricate a contact-type head having contact pads and a polarization maintaining fiber, because this type of aperture can only effectively function under a condition of both extremely small spacing and with applied polarized light. The head is fabricated mainly by photolithography. By controlling process conditions, we obtain contact pads at nm accuracy. A measurement of surface configuration using an interferometer shows that the aperture and the contact pads are almost on the same plane within 10 nm. The medium consists of a glass substrate, a titanium layer, a carbon protective layer, and a lubricant layer in this order. Line-and-space (L&S) patterns whose widths are 40-200 nm are formed on the titanium layer. The contact head approaches the medium surface, and then the medium is scanned by a piezo stage. The near-field light generated from the triangular aperture is scattered by the L&S pattern and detected by a photomultiplier tube. Signal readout from the 40 nm-wide L&S patterns is demonstrated with a 170 nm-wide triangular aperture.