30 to 50 ns liquid-crystal optical switches.

The optical switching time of twisted-nematic liquid-crystal cells using the liquid crystals, 5CB (C(5)H(11)-Ph-Ph-CN), 5OCB(C(5)H(11)-O-Ph-Ph-CN) and PCH5 (C(5)H(11)-Cy-Ph-CN) have been characterized as a function of temperature, bias voltage and switching voltage, V. The transition time from 90% to 10% transmission scales as V(-1.9) and is limited to 30 to 50 ns by the liquid-crystal breakdown electric field, ~100 V μm(-1). The time from the initial switching voltage step to 90% transmission, delay time, decreases with increasing bias and switching voltage. For 5CB and 5OCB the delay time approaches a constant value at higher electric fields, >10 V μm(-1). Both the transition and delay times decrease with increasing temperature. The minimum transition time 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.