Embossing Reactive Mesogens: A Facile Approach to Polarization-Independent Liquid Crystal Devices

摘要

Reactive mesogens (RMs) are used in a wide variety of applications, from retardation plates for organic light-emitting display screens, liquid crystal phase stabilization, optical or electrically active elastomers to novel optic components. They can be processed as standard liquid crystals and subsequently polymerized to stabilize both shape and anisotropic properties. However, creating complex shapes while maintaining good alignment of the RM optical axis can be a challenge. In the present work, embossing is used to replicate a wide variety of RM structures in several electro-optic devices. A novel device geometry is proposed where a polarization-independent lens is formed by opposing birefringent Fresnel zone plates embossed in aligned RM. The RM forms the optical elements and alignment layers for an index-matched liquid crystal, arranged to produce the twisted nematic configuration. Low voltages switch the device between nonfocusing and focusing states. After characterizing lens efficiency and beam properties, the method is used to fabricate a switchable multilevel Fresnel zone plate with optical efficiencies beyond 50%, and theoretically able to produce polarization-independent lenses with efficiencies approaching 100% from a single structure. Finally, manufactured polarization-independent gratings and microlens arrays are presented using the method to illustrate the wide range of applicability.