Highly efficient photorefractive composites based on layered photoconductive polymers

High-performance photorefractive materials based on the layered photoconductive polymers PPT-CZ [rigid backbone of poly(p-phenyleneterephthalate) with pendent carbazole groups] are studied. The composites are composed of PPT-CZ and are doped with the sensitizer C60 and nonlinear optical chromophores. Despite the absence of a plasticizer and the lower concentration of the carbazole photoconductive moieties as compared with poly(N-vinyl carbazole), these materials show high photorefractive sensitivity, i.e., Sn2 of 70± 7 cm2/kJ at E0=100 V/μm for PPT-CZ(n=12):diethylaminodicyanostyrene:C60. The low glass transition temperature (<0°C) leads to a high rotational mobility of the chromophores that results in large refractive-index changes. For all the composites that were investigated, the two-wave mixing gain Γ exceeds 100 cm-1 at an applied field of 50 V/μm.

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