Today, polymeric photorefractive (PR) composites are considered to be promising for optical applications such as real-time holography; including optical correlation and real-time image processing, phase conjugation, neural networks, high-density holographic storage, and more. Space charge field (Esc) formation and chromophore reorientation are the crucial processes to perform the photorefractivity, since both the index contrast and the response time of PR grating are closely related with the Esc strength and electro-optic nonlinearity. In particular, the spatially varying charge distribution responsible for Esc formation depends on photoconductivity, including the dynamics of charge generation, transport, trapping, and detrapping in the materials.
In this work, we investigated the influence of key components for PR effect, such as photosensitizer, photoconducting polymer, NLO chromophore, and temperature, on the space charge field formation and discuss the effect of space charge field on the dynamic and steady-state photorefractive performance. At 632.8nm, photo-charge generation efficiencies, photoconductivities, space charge fields, four wave mixing diffraction efficiencies, gain coefficients, and phase shifts were measured as a function of external electric field and temperature. Then, on the basis of experimental results, the relation between the key parameters and the photorefractivity is analyzed and discussed.
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