Quantitative measurements on the threshold of mechanically induced buckling instabilities are presented. We report the data obtained by light scattering experiments, and by optical spectroscopy measurements. We verify de Gennes’ model for this instability qunatitatively, in analogy with the smectic A case, obtaining an equivalent penetration length of the order of the cholesteric pitch length. The distribution of the deformation versus the position of the light spot on the sample is reported.
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