Electrooptic response of reflective-mode, pi/4-twisted-nematic liquid crystal cell in the voltage regions close to and distant from the Freedericksz transition threshold

Two reflective-mode, pi/4-twisted-nematic liquid crystal cells were prepare d using E7 and ZLI4801-000 liquid crystals and their electrooptic responses were measured in the voltage regions close to and distant from the Freeder icksz transition threshold. Our reflectivity data distant from the threshol d voltage (V-th) could not be described by the model that assumed a lineari zed distribution of the twist angle across the cell and considered the volt age dependency of the tilt angle to follow the equation suggested by Lu and Saleh [Appl. Opt. 30 (1991) 2354], although the fit is good near V-th. We determined that the reflectivity in the voltage region distant from V-th Sh ould be calculated using the model that considers the distributions of the tilt angle and the twist angle. The director-axis distributions were obtain ed from the numerical integration of the Ericksen-Leslie equation.