Photorefractive Smectic Mesophases

The orientational contribution pointed out the major contribution of the molecular first order susceptibility to the index modulation in organic photorefractive materials. This discovery leads the way to the use of liquid crystals as PR materials due to their spontaneous birefringence and to the many possible electric field-induced reorientational effects. In this chapter, we are focusing on the structure and electro-optic properties of the smectic phases. After a brief introduction to the different phases (A and C), we will discuss the specific properties each phase contribute to in a photorefractive liquid crystal system. The theory of the molecular alignment into the photo-generated space-charge field is detailed incorporating the particularities due to liquid crystal phases and light polarization. Some specific cases are analyzed in detail such as the application of an AC field and the use of bistable devices which bring both long-term stability and nondestructive readout.