Liquid-Crystal Optical Switches

The optical switching times of liquid-crystal cells using 5CB, 5OCB and PCH5 liquid crystal materials have been characterized as a function of applied voltage, V, and temperature, T. The transition time from 90 to 10 % transmission scales as V and is limited to 50 to 30 ns by the breakdown electric field, ~ 10 V cm of the liquid crystal. The time from the initial voltage step to 90 % transmission, delay time, decreases with increasing voltage and approaches a constant value at higher electric fields, >10 V cm. Both the transition and delay times decrease with increasing temperature. The minimum transition times at temperatures a few degrees below the nematic-isotropic temperature are 32, 32, and 44 ns and delay times are 44, 25 and 8 ns for 5CB, 5OCB, and PCH5 respectively.