Rewritable High-Density Optical Recording on Azobenzene Polymer Thin Film

An optical recording method was proposed by means of a multiple-code inscription on photo-responsible polymer as a photo-induced surface relief (PSR). The inscribed PSR patterns are erasable and re-writable. The multiple-coding method is based on the combination of angular- and depth-gradations. Expected numbers of the information code recorded on one pit are (n + 1)m, here m and n are angular- and depth-multiplicity, respectively. Therefore, the recording density is expected to be increased exponentially along with the increase of the angular- and depth-multiplicity. For the first attempt, it was confirmed that a recording pit 100 μm square with the multiplicity of m = 6 and n = 4 could be recorded and read out. This result indicates that the recording density of 1 GB/inch2 was achieved.