[OPTICAL REVIEW Vol. 17, No. 5 (2010) 486-494]
© 2010 The Japan Society of Applied Physics

Optical Head with Metal Cladding in Asymmetrical Butted-Grating Structure for Small Thermal Spot in Laser-Assisted Magnetic Recording

Shin-ya HASEGAWA, Fumihiro TAWA1, and Wataru ODAJIMA2

Human Centric Computing Laboratories, Fujitsu Laboratories Ltd., 10-1 Morinosato-Wakamiya, Atsugi, Kanagawa 243-0124, Japan
1Enterprise Server Business Unit, Fujitsu Ltd., 4-1-1 Kamikodanaka, Nakahara-ku, Kawasaki 211-8588, Japan
2Technical Computing Solutions Unit, Fujitsu Ltd., 9-3 Nakase 1-chome, Mihama-ku, Chiba 261-8588, Japan

(Received February 2, 2010; Accepted July 30, 2010)

A planar near-field optical head with a high optical efficiency of 12.9% (3.2 times higher than that of our previous design) for laser-assisted magnetic recording is described. In this head, a slab-type waveguide with a narrow core is butt-coupled into a one-sided multilayer thin-film stack. Metal cladding is used in the core because of its high optical efficiency due to surface plasmon excitation. To keep production costs low, we use only two layers for the side part, which act as a two-index-step lens that couples light in the side part into a core of the central part. We optimized the parameters of this optical head and recording medium by means of an optical simulator using the finite-difference time-domain method and a thermal simulator. The calculated full width half maximum (FWHM) optical spot size on the recording medium is 24× 47 nm2 and the thermal spot size is 80× 88 nm2 (FWHM).

Key words: optical waveguide, laser-assisted magnetic recording, near-field optics, magnetic recording medium, \\FDTD method