Speed enhancement of photorefractive polymers by means of light-induced filling of trapping states

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Abstract
The fastest organic photorefractive materials show response times in the millisecond range. The origin of this limit is not yet fully understood. Charge-carrier generation and transport processes and reorientation of the nonlinear-optical chromophores may play an important role. We characterize a new photorefractive guest–host polymer by cw two-beam coupling, as well as by cw and pulsed four-wave mixing experiments. The latter were used to determine unambiguously the response time of the material. We show that a decrease of the response time by a factor of 1000 can be achieved by illuminating the sample with a strong cw beam during pulsed exposure. A model of the enhancement process backed by dc photoconductivity measurements is presented.