Inch-scale graphene-based LC tunable phase retarders: Experimental study of surface interaction between liquid crystal-polyimide-graphene layers

Recently Liquid Crystal (LC) devices open new route for the next generation optical elements revealing on novel materials that come to a scene, among which graphene endorse amazing capabilities. Herein, we perform detailed study of the surface interaction between LC molecules, graphene (single and multilayer) and alignment layer during assembling tunable LC phase retarders on arbitrary substrates. By considering the surface free energy of graphene a proper selection of polyimide (PI) as a polar layer for non-contact planar alignment of LC molecules is presented. Surface anchoring energy and pre-tilt angle value have been determined to characterize the interfaces at the boundary and their impact on the dynamic performances of assembled LC devices. Besides the excellent phase modulation repeatability over the large-scale area of retrofitted LC structures, an electrically tunable LC phase retarder supported by graphene on PDMS substrate that exhibits great potential for future ITO-free integrated photonic devices and bio-oriented technologies is demonstrated.