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Soft Matter and Biological Physics
Eur. Phys. J. E 3, 11-20 (2000)
DOI: 10.1007/s101890070036

Electro-optical phase shift in polymer dispersed liquid crystals

O. Levy

Courant Institute of Mathematical Sciences, New York University, New York, NY 10012, USA

ohad@cims.nyu.edu

(Received 25 November 1999 and Received in final form 20 January 2000)

Abstract
An anisotropic version of the Maxwell Garnett approximation is applied for studying the electro-optical phase modulation by polymer dispersed liquid crystals (PDLC). The PDLC contain bipolar liquid crystal droplets that can be reoriented by an external field causing a change in the optical birefringence. This approach provides an explicit link between the droplet orientation distribution and the electro-optical phase shift. For aligned droplets we find that the sharpness of the change in the birefringence may be controlled by selecting the initial orientation. For a planar distribution we find sharp transitions with a hysteresis loop whose width depends on the droplet concentration. For a random distribution, the droplet orientation and the optical phase shift change more gradually with the applied field. These results demonstrate that PDLC may be suitable for a wide range of electro-optic applications based on their field-induced phase modulation properties. In addition, it is apparent that the optical phase shift is quite sensitive to changes in droplet orientation. It should therefore be useful for studying reorientation phenomena in PDLC, overcoming the problems due to light scattering in these materials.

PACS
42.70.Df - Liquid crystals.
78.20.Jq - Electro-optical effects.
78.66.Sq - Composite materials.

© EDP Sciences, Società Italiana di Fisica, Springer-Verlag 2000