J. Phys. II France
Volume 5, Number 3, March 1995
Page(s) 349 - 354
DOI: 10.1051/jp2:1995136
J. Phys. II France 5 (1995) 349-354

Birefringence Modulated Scattering in Gels

Cyrille Rochas, Anne-Marie Hecht and Erik Geissler

Laboratoire de Spectrométrie Physique CNRS associate laboratory, Université J. Fourier de Grenoble, 38402 St Martin d'Hères Cedex, France

(Received 5 December 1994, accepted in final form 5 January 1995)

We describe a novel effect that arises when a monochromatic light beam passes through a deswollen rigid-rod gel. When viewed perpendicular to the direction of propagation, under suitable conditions of polarisation, a pattern of fringes is observed. The phenomenon is a simple geometrical optical effect caused by the birefringence of the sample. For a given wavelength $\lambda$ of incident light, observation of the spatial frequency of the fringes, $\frac{\Delta n}{\lambda}$, offers an inexpensive means of measuring the magnitude of the birefringence $\Delta n=\vert n_{\vert\vert}-n_\perp \vert$. With white incident light, the fringes transform into an iridescent pattern.

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