Disclosed is an optical recording medium comprising a recording layer. The recording layer contains: a charge generation material generating an electron and a hole by light irradiation; a charge transport material transporting one of the electron and the hole; a charge trap which traps the transported one of the electron and the hole to separate the electron and the hole; and a non-linear optical material which changes optical properties of the recording layer in accordance with electric field formed by the electron and the hole being separated from each other. The non-linear optical material has an asymmetrical carbon atom and a cyclic group. Or, it is a cyclic-group-containing constituent having: an inversion symmetric pi-electron system; at least one of an electron donating group and an electron accepting group which are bonded to the inversion symmetric &pgr;-electron system; and an asymmetrical carbon atom.
To achieve high performance in molecularly dispersed photorefractive polymer films, it is essential to have a large electro-optic coefficient (r33), which is obtained by orientating nonlinear optic (NLO) molecules in an external electric field applied across the film. We investigated high-temperature casting, which is a new material fabrication technique for this purpose. We found that samples prepared by casting at higher temperatures showed a larger value of r33, which was due to an increasing number of unpaired NLO molecules in the polymer matrix that were able to orientate in an external electric field. This was caused by releasing stable anti-parallel pairs that were formed between the NLO molecules due to their large dipole moment. Therefore, our samples showed a large improvement in their photorefractivity in four-wave mixing (FWM) experiments.