High-performance of PVK-based photorefractive polymers by high-temperature casting

To achieve high performance in molecularly dispersed photorefractive polymer films, it is essential to have a large electro-optic coefficient (r(33)), 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 r(33), 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.