Nonlinear Electrooptical Measurements in the Smectic-Cα*Phase

We performed electrooptical measurements in the smectic-Calpha* (SmCalpha*) phase of the antiferroelectric liquid crystal, 4-(1-methyl-heptyloxycarbonyl)phenyl 4-octylcarbonyloxybiphenyl-4-carboxylate (MHPOCBC), and showed that the frequency dispersion of the second-order electrooptic response strongly depends on the angle between the polarizer and the layer normal while that of the linear response does not. Usually in the SmCalpha* phase we can observe both the amplitude mode and the ferroelectric mode by second-order electrooptic spectroscopy. In a particular experimental condition, we succeeded in suppressing the ferroelectric mode contribution in the frequency dispersion spectrum and clearly observed only the amplitude mode. The results were discussed and analyzed on the basis of the phenomenological theory.