Europhys. Lett, 48 (6), pp. 634-640 (1999)
Non-linear dynamics of the electro-optic response of confined liquid crystals
M. Buscaglia 1,4, T. Bellini 1,4, V. Degiorgio 1,4
F. Mantegazza 2,4 and F. Simoni 3,4
1Dipartimento di Elettronica, Università di Pavia - via Ferrata 1, 27100 Pavia,
2Dipartimento di Fisica, Università "Bicocca'' - 20133 Milano, Italy
3Dipartimento di Scienze dei Materiali e della Terra, Università di Ancona
60131 Ancona, Italy
4Istituto Nazionale per la Fisica della Materia - Italy
(received 26 May 1999; accepted in final form 20 October 1999)
PACS. 61.30Eb - Experimental determinations of smectic, nematic, cholesteric, and other structures.
PACS. 78.35 - Brillouin and Rayleigh scattering; other light scattering.
We have experimentally studied the electro-optic response of two different classes of systems consisting of a nematic liquid crystal either dispersed into a solid polymer matrix or mixed with aggregated silica particles forming a random gel network. By monitoring the time evolution of the optical transparency of the system under the action of electric field pulses, we have found that the response times depend in an intriguing and non-monotonic fashion on the field strength. We show that the observed nonlinear behavior can be interpreted by a simple visco-elastic model of the liquid crystal domains combined with an accurate description of their light scattering cross-section.
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