Tunable Beam Steering at Terahertz Frequencies Using Reconfigurable Metasurfaces Coupled With Liquid Crystals

Abstract

Metasurfaces with a spatially varying phase profile enable the design of planar and compact devices for manipulating the radiation pattern of electromagnetic fields. Aiming to achieve tunable beam steering at terahertz frequencies, we numerically investigate metasurfaces consisting of one dimensional arrays of metal-insulator-metal (MIM) cavities infiltrated with liquid crystals (LCs). The spatial phase profile is defined by a periodic voltage pattern applied on properly selected supercells of the MIM-cavity array. By means of the electro-optic effect, the voltage controls the orientation of LC molecules and, thus, the resulting effective LC refractive index. Using this approach, the spatial phase profiles can be dynamically switched among a flat, binary, and gradient profile, where the corresponding metasurfaces function as mirrors, beam splitters or blazed gratings, respectively. Tunable beam steering is achieved by changing the diffraction angle of the first diffraction order, through the reconfiguration of the metasurface period via the proper adjustment of the applied voltage pattern.