Largely Tunable Terahertz Circular Polarization Splitters Based on Patterned Graphene Nanoantenna Arrays

Dynamic manipulation of wavefront is vital for massive free-space optical applications. Here we propose a set of largely tunable circular polarization splitters leveraging graphene nanoantennas with high efficiency reaching 83% and wide frequency tunability range of 2 to 5 THz. By synergizing the electrically tunable surface plasmons of graphene with phase gradient metasurface, we numerically demonstrate two kinds of polarization splitters with complimentary graphene patterns to realize electrical tuning of operation frequency and efficient circular polarization demultiplexing. Using antennas of different geometric sizes, the device performances are investigated in several different terahertz bands. Our proposed structures can facilitate dynamically tunable broadband and high-speed applications such as polarization demultiplexing and optical switches in terahertz regime.