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 in 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 mu m 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/inch(2) was achieved. (c) 2005 The Optical Society of Japan.