Photo-controllable tristable optical switch based on dye-doped liquid crystal

• This work demonstrates an optically switchable tristable optical switch.
• Tristable attenuation, scattering, and transparent states can be achieved.
• All states can be switched through light-induced isomerization effect of azo-chiral.

This work demonstrates an optically switchable tristable optical switch that is based on the light-matter interactions of dichroic dyes, azo-chiral and liquid crystal. The photo-induced isomerization of the azo-chiral dopant can alter the thickness/pitch ratio of liquid crystal film and enable the homeotropically aligned device to exhibit three stable – fingerprint, focal conic, and homeotropic textures. The dichroic dyes in the three textures have different absorptive properties. Tristable attenuation, scattering, and transparent states can be achieved using the dichroic dye doped fingerprint, focal conic, and homeotropic textures, respectively. All states can stably exist for several hours, and be switched from one state to another through light-induced isomerization effect of azo-chiral. Such a multi-stable optical switch exhibits easy switching, a desirable contrast ratio, and low power consumption. It therefore exhibits the potential to be utilized in practical portable information systems.