Title: Fast and in-plane only retardation switching of a certain type of smectic liquid crystal

Abstract

A certain type of the smectic single domain or SSD liquid crystal shows some unique characteristic properties including fast optical response such as ~ 100 microseconds, applied electric field polarity dependent response, and in-plane only retardation switching. Dynamic switching behavior of retardation switching of an SSD liquid crystal has revealed some interested phenomena. In plane only and amixture between in plane and out of plane retardation switching behaviors are highly related to the initial smectic liquid crystal molecular stacking configurations and their consecutive liquid crystal driving torque origin. With uniformly stacked configuration, a completely symmetric retardation switching, as well as light throughput behavior was obtained. With a slight twisted stacking configuration, the retardation switching behavior is dependent on the applied electric field strength, which may change the initial molecular stacking configuration, resulting in either symmetric or asymmetric retardation switching. When the molecular stacking has twisted heavily, the obtained retardation switching showed asymmetric behavior regardless of the applied electric field strength. When an SSD liquid crystal shows completely in-plane only retardation switching, the SSD liquid crystal molecules always move perpendicular to the externally applied electric field, and switching direction either clockwise, or counter-clockwise is dependent on applied electric field polarity. For instance, when applied electric field is downward to the SSD liquid crystal layer, each SSD liquid crystal molecule swings to clockwise direction as a corrective manner. When the applied electric filed is upward, the swing direction is counter-clockwise. Such always switching perpendicular to the applied electric field direction suggests the primary driving torque of the SSD liquid crystal originated from quadrupole momentum. An original smectic liquid crystal molecular stacking configuration is assumed to give some significant influence on commensurate effect of quadrupole moment origin. Fast optical response with in-plane only retardation switching of an SSD liquid crystal would be good for high diffraction efficiency devices, beam steering devices, and some photonics devices.