Abstract
Scanning near-field optical microscope is able to achieve a nanometer spatial resolution, and is useful for
visualization of elementary excitations in nanomaterials. Combination of the near-field optical
microscope with the time-resolved spectroscopy enables us to visualize spatio-temporal behaviors of the
excited states. We apply this imaging technique to the studies of static and dynamic optical properties of
single gold nanorods. The static near-field image of a single gold nanorod shows a periodic oscillation
along the long axis of the nanorod, and is attributed to a plasmon mode resonantly excited. The dynamic
near-field image of the nanorod shows a characteristic spatial feature, which is very different from that of
the static image. We discuss the origin of the dynamic near-field image, and the image is assigned to
variations of plasmon modes induced by the photo-excitation. We also discuss the future prospect of the
dynamic near-field microscopy and its applications to fundamental studies on plasmonic materials.
