Electrically controllable liquid crystal paraxial Fresnel zone plate based on concentric zones patterned electrode

Abstract

A twist nematic liquid crystal Fresnel zone plate (LCFZP) with controllable diffraction efficiency based on concentric zones patterned electrode is demonstrated. The alternating “transparent” and “opaque” state occurs when the LCFZP placed between two crossed polarizers. When the electric field was applied to the odd (even) zones, the odd (even) zones were dark, and the even (odd) zones were bright. The diffraction efficiency was varied with changing the voltage or by rotating the incident polarization direction. The maximum diffraction efficiency can reach 37.8% which is close to the theoretical limit of 40.5%, and the response time is reasonably fast. The proposed LCFZP with the advantages of easy fabrication, compact structures, low power consumption, and good stability, which has potential applications in many modern optical devices.