Physical Aspects of Electro-optic Properties of Smectic Liquid Crystals

We present an E ective Internal Field Model for the antiferroelectric (AF) to eld induced ferroelectric (FF) transition of smectic CA. This model attributes the fast dynamics and high threshold elds of this transition to the large magnitudes of its in-plane polarization. We conclude that propagating ngers observed in the vicinity of the AF $ FF threshold eld can only be observed in holding elds where there are metastable states. We argue that this is because relaxation times for antiferroelectric liquid crystals (AFLCs) are too fast ( s) for front propagation of stable states into unstable ones. The model is also used to interpret the decrease in threshold eld when smectic C* is added to CA.