Linear and non-linear electro-optic studies of the smectic-A- smectic-C-alpha* phase transition

Electro-optical measurements have been performed around the SmA-SmCalpha* p hase transition point in antiferroelectric liquid crystals MHPOBC and MHPOC BC. In both materials the soft mode condensation is clearly seen in additio n to the partial softening of the ferroelectric soft mode. The Curie Weiss law is observed. The comparison of th, slopes of these modes shows that MHP OBC and MHPOCBC should be close to the critical point. In addition to these soft modes, a low frequency mode was detected.