Characterization of Liquid Crystal Complex Dielectric Constants Based on Localized Surface Plasmon Polaritons

Liquid crystal (LC), as an anisotropic material, has attracted much attention in high frequency microwave and millimeter wave applications due to its tunable dielectric properties. It has great influence on the design of reconfigurable microwave devices like tunable phase shifters, beam-steering antennas and filters. Therefore, the accurate characterization of LC dielectric properties is highly valued that the design and optimization of reconfigurable microwave devices. In this paper, a device for measuring LC dielectric properties based on SLSP is proposed. The device makes full use of SLSP's high sensitivity, high Q factor and relatively consistent electric field line direction to detect the transmission response. Moreover, for anisotropic materials to be measured, the device applies an external bias electric field to change the electric field line and its angle to extract the complex dielectric constant. The perturbation method utilizes S-parameters to compute the complex dielectric constants of LC molecules in both horizontal and vertical states. The extraction results from a variety of standard samples have validated the effectiveness of the proposed method.