Measurements of the director fluctuations in nematics by speckle interference

Abstract

Orientational fluctuations in nematics were experimentally investigated by homodyne speckle interference. Thermally excited fluctuations are local stochastic events. Such fluctuations in most cases relax in time aperiodically. In this experiment fluctuations were incidentally observed, and they could oscillate during some life-time before decaying. They were correlated spatially over an area of relatively large size. For convenience, large oscillating fluctuations, correlated in time and space, are called in this report "fluctuons". Usually, the fluctuons observed in the experiment had several oscillating cycles. An average lifetime of single fluctuons measured was a few miliseconds. The fluctuons have thermal origin but their average amplitude and probably also the correlation length could have been enhanced by electric DC, low frequency or optical field (in the linear range), even in the range below the re-orientational threshold intensity.

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References:

1. M. Yoneya, Y. Utsumi, Y. Umeda, J. Appl. Phys. 98, 16160 (2005).
2. I.C. Khoo, Y. Liang, Phys. Rev. E 65, 5 (2000)
3. J. Papanek, Mol. Cryst. Liq. Cryst. 179, 139 (1990).[CrossRef]
4. P. Oswald, P. Pieranski, Nematic and Cholesteric Liquid Crystals(Taylor and Francis, London, 2005).
5. I.C. Khoo, S.T. Woo, Optics and nonlinear optics of liquid crystals, (World Scientific Publishing, 1993).
6. J.C. Filipini, Phys. Rev. Lett. 39, 150 (1977).[CrossRef]
7. P.G. de Gennes, The physics of Liquid Crystals, (Clarendon, Oxford 1973).
8. N.V. Tabiryan, A.V. Sukhov, B.Ya. Zeldovich, J. Opt. Soc. Am. B 18, 8 (2001).[CrossRef]
9. P. Galatola, J.Phys.II France, 2 1509 (1992)