Electrically controllable and polarization-independent Fresnel zone plate in a circularly symmetric hybrid-aligned liquid crystal film with a photoconductive polymer layer

This work reports a Fresnel zone plate in a circularly symmetric hybrid-aligned liquid crystal (LC) film with a photoconductive polymer layer. An ultraviolet-induced electrodelike pattern of polymer layer under a zone plate photomask results in alternating major and minor portions of external voltage dropping on LC layer in conductive and nonconductive regions, respectively. These effects cause the discrepancy in LC reorientation between adjacent zones, generating a Fresnel zone plate. The focusing of the zone plate is electrically controllable and polarization independent. Additionally, the zone plate has advantages of a zero focusing in the voltage-off state and a very small operating dc field range from 0 to 0.3 V/μm.