Photorefractive polymeric composites with high two-beam coupling gain without external electric field

Herein, three photorefractive (PR) composite films were fabricated. They consist of poly (N-vinycarbazole) (PVK, 33 wt %), 2, 5-dimethyl-(4-p-nitrophenylazo) anisole (DMNPAA, 50 wt %), ethyl carbazole (ECZ, 16 wt %) and fullerene derivatives (1 wt %). The three fullerene derivatives [6, 6]-Phenyl-C61-butyric acid isopropyl ester (PCBIPE), [6, 6]-phenyl-C61-sec-butyl butyrate (PCSBB), and [6, 6]-phenyl-C61-phenethyl butyrate (PCPEB) were used as photosensitizer in the PR films. The PR composite films PVK/DMNPAA/ECZ/PCBIPE(33/50/16/1), PVK/DMNPAA/ECZ/PCSBB(33/50/16/1), and PVK/DMNPAA/ECZ/PCPEB(33/50/16/1) (in wt %) with a low glass transition temperature (21.3 degrees C) can easily be fabricated into optically transparent films, The PR performances of the three PR composite films were investigated by two-beam coupling (TBC) experiment at 633 nm wavelength. The results illustrate that the TBC signals were observed under no external electric field or pre-poling condition. The maximum TBC gain of 43.90 cm(-1) for PVK/DMNPAA/ECZ/PCPEB(33/50/16/1) PR composite films. The reason of TBC gain of PR materials at zero electric field was discussed.