The effect of laser wavelength on the photorefractive characteristics of PMDA-DR19 based photorefractive polymeric materials

Abstract

The photoconductivity and photorefractive characteristics of PMDA-DR19-based photoconducting nonlinear optical polymeric films with different compositions were studied using red and green lasers. Contributions of dopants and the host to the photoconductive and photorefractive properties are systematically discussed. The virgin nonlinear optical material PMDA-DR19 was neither photoconductive nor photorefractive in nature. However, it became photoconductive and photorefractive once the charge transport material was incorporated into the PMDA-DR19/PVB polymer film. Films containing more nonlinear optical chromophore exhibited higher diffraction efficiency. Response speed was further elevated when an additional charge generation material was doped in. Diffraction grating was observed under zero electric field and was confirmed due to a photorefractive effect by the two-beam coupling effect. In addition to composition modification, the laser light source was also an important factor in changing the PR response speed. The photorefractive response speed was tremendously improved when films were written and read by two different laser beams, either red/green lasers or green/red lasers. (C) 1997 Elsevier Science Ltd.