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

Reactive mesogens (RMs) have been used in a wide variety of applications, from retardation plates for OLED screens, liquid crystal phase stabilisation, optical or electrically active elastomers to novel optic components. They can be processed as standard liquid crystals and subsequently polymerised to stabilise 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 polarisation-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 form the twisted nematic configuration. Low voltages switch the device between non-focusing and focusing states. After characterising lens efficiency and beam properties, the method is used to fabricate a switchable multi-level Fresnel zone plate with optical efficiencies beyond 50 %, and theoretically able to produce polarisation independent lenses with efficiencies approaching 100% from a single structure. Finally, manufactured polarisation-independent gratings and microlens arrays are presented using the method to illustrate the wide range of applicability.