Imaging of digital versatile rewritable disc using the reflection-mode scattering-type scanning near-field optical microscope

Recording marks written on the digital versatile rewritable disc (so called DVD-RAM) by a blue violet laser diode were observed using a reflection-mode scattering-type scanning near-field optical microscope (RS-SNOM) for the first time. The RS-SNOM is based on the atomic force microscope (AFM) and thus both the AFM and SNOM observations are simultaneously performed. In the AFM image, the land/groove structure was clearly observed and no other contrast appeared, while in the SNOM image, the 180-nm-long recording marks were clearly observed at the position of the groove. The contrast originated from the difference in the refractive index, faithfully traced in the SNOM image with a resolution of 50 nm. This result indicates that the RS-SNOM can be used as an observation tool for the next-generation high-density optical media.