All-optical terahertz logic gates based on coupled surface plasmon polariton sub-wavelength waveguiding in bulk Dirac semimetal

Bulk Dirac semimetals (BDS) are quantum fermionic system also identified as three-dimensional counterpart of graphene exhibit rich plasmonic response at terahertz (THz) frequencies. In this work, we report THz waveguiding in the BDS curved geometries, which confine electromagnetic field in the form of symmetrically coupled surface plasmon polariton (SPP) modes. We demonstrate how the sub-wavelength BDS-Air-BDS multilayer system with various bending and corners efficiently confines THz beam with minimal bending losses. The realized sub-wavelength THz waveguiding in BDS system is advantageous than other approaches like zero-refractive index metamaterials. Based on the symmetric coupled SPP waveguiding in BDS multilayers, all-optical logic gates including OR, AND, XOR, NOR and NAND are realized at THz waveband. The realized THz logic gates exhibit optimal threshold transmission (at least 50%) for defining ON-OFF states. We anticipate that the illustrated waveguiding and logic gate applications in BDS system could open an avenue for optoelectronic applications at THz frequencies.