Noriko HOSAKA¹ and Toshiharu SAIKI^1,2

¹Near-Field Optics Group, Kanagawa Academy of Science and Technology, KSP East 409, 3-2-1 Sakado, Takatsu-ku, Kawasaki 213-0012, Japan
²Department of Electronics and Electrical Engineering, Keio University, Hiyoshi, Kohoku-ku, Yokohama 223-8522, Japan

(Received December 29, 2005; Accepted March 3, 2006)

We demonstrate high-resolution fluorescence imaging of single molecules using near-field scanning optical microscopy (NSOM) with a tiny aperture probe for two different wavelengths in visible range in the illumination mode of operation. The spatial resolutions obtained at both excitation wavelengths were almost the same and the highest resolution realized was about 10 nm. To discuss the achievable resolution in aperture NSOM, we also employed a computer simulation by the finite-difference time-domain method for various aperture sizes and wavelengths. The resolution of 10 nm is predicted to be contributed by the single peak of localized near-field light around the rim of the aperture.

Key words: near-field scanning optical microscopy (NSOM), aperture probe, high spatial resolution, single molecule, fluorescence imaging, finite-difference time-domain (FDTD) method