High-Speed and Precise Gap Servo System for Near-Field Optical Recording

• Published in: Japanese Journal of Applied Physics Vol. 51; no. 8; pp. 08JA04 - 08JA04-4
• Main Authors: Koide, Daiichi, Kajiyama, Takeshi, Tokumaru, Haruki, Takano, Yoshimichi, Nabata, Yuta, Ogata, Tokoku, Miyazaki, Toshimasa, Ohishi, Kiyoshi
• Format: Journal Article
• Language: English
• Published: The Japan Society of Applied Physics 01.08.2012
• ISSN: 0021-4922; 1347-4065
• DOI: 10.1143/JJAP.51.08JA04

We propose a high-speed and precise gap servo control system that is based on the feed-forward control method that can reduce the harmonic disturbance (RHD-FFC) on a near-field optical recording system with a solid immersion lens. An optical disk of 1.2 mm thickness rotates with about 30 μm of axial run-out. The axial run-out prevents a gap servo from performing precisely at high rotational speed. The RHD-FFC method can suppress harmonic disturbances of gap error signal and can perform at high speed while keeping less than 25 nm of gap length between an optical head and a rotational disk surface. We confirmed that the gap servo applying the RHD-FFC method performed precisely and achieved at high disk rotational speed of 11000 rpm with a 1.2-mm-thick optical disk with a track pitch of 0.16 μm, corresponding to a data capacity of 100 Gbyte.