High-resolution examination of recording marks in phase-change media using a scanning near-field optical microscope

Recording marks in digital versatile disc-random access memory (DVD-RAM) were examined using a scanning near-field optical microscope (SNOM) incorporating an improved probe tip design. The marks were recorded on an experimental DVD-RAM medium with a track-pitch of 0.6 mu m. The tip size of the SNOM was made wider than the track width in order tb avoid optical ghosting arising from the track edge. The recording power was varied in order to investigate the dependence of the mark shape on power and it was found that the mark shape correlated well with the reproduced signal. The SNOM is considered-to be a good candidate for a practical characterization tool for optical recording media.