**6. Conclusions**

that the hologram image (refractive index grating) formed in the FLC was rewritten with sufficient speed to project a smooth reproduction of the holographic movie. This result shows that a hologram image was formed at the interference area in the FLC material and that

λ

 

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**Figure 29.** Dynamic hologram formation experiment on an FLC sample. A computer-generated animation was dis‐ played on the SLM. The SLM modulated the object beam (488 nm), which was irradiated on the FLC sample and al‐ lowed to interfere with the reference beam. The readout beam (633 nm) was irradiated on the FLC and diffraction was

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contributes to the optical image amplification.

148 Ferroelectric Materials – Synthesis and Characterization

 

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<sup>λ</sup> 

observed.

 

Real-time dynamic amplification of optical image signals was demonstrated in photorefractive FLC blends. The response time was of sub-millisecond order and was dominated by the formation of an internal electric field. The photorefractive effect of FLCs was significantly dominated by the properties of the FLCs. Aside from spontaneous polarization, viscosity, and the phase transition temperature, the homogeneity of the SS-state was found to be a major factor. The gain coefficient and the response time were also significantly dominated by the homogeneity of the SS-state. Therefore, a highly homogeneous SS-state is necessary to create a photorefractive device. A gain coefficient higher than 1200 cm-1 and a response time shorter than 1 ms were obtained with application of only 1.5 V/μm in a photorefractive FLC blend. This response time is sufficiently short for real-time dynamic holograms. FLC mixtures containing photoconductive chiral dopants exhibited high gain coefficients and fast responses, which confirms their usefulness in photorefractive device applications.
