High-speed PVK-based photorefractive polymer composites

The polymer composites under investigation consist of the hole-transporting polymer poly(N-vinylcarbazole) (PVK), the charge generating molecule 2,4,7-trinitro-9-fluorenone (TNF), the plasticizer 1,3-bis(N-carbazolyl) propane (BisCzPro), and nonlinear optical (NLO) chromophore. We carried out a series of measurements in order to characterize the photorefractive polymers: transmission spectrum; glass transition temperature T_g; speed of reorientation under the application of an electric field of 54 V/μm and birefringence induced by the applied field using a polarimetric technique; photorefractive diffraction efficiency and response time as a function of incident intensity using a four-wave mixing geometry; and photorefractive gain coefficient and the photorefractive phase shift using a two-wave mixing geometry. We have successfully accelerated the response of NLO chromophores by modifying the structure of DNMAA without any degradation of diffraction efficiency. The photorefractive response of our samples is limited by the formation of space charge distribution.