Active terahertz spin Hall effect in vanadium dioxide metasurfaces.

ABSTRACT

Insulator-to-metal transition induces large material property variations in vanadium dioxide (VO2) over a broad frequency band. VO2, therefore, has been introduced into metallic resonating structures to realize reconfigurable metadevices from microwave to optical wavelengths. Beyond enabling metal/VO2 hybrid meta-atoms, in the THz regime metallic-phase VO2 micro-structures can support strong electromagnetic resonances, offering great potential in active manipulation of THz radiation. In this paper, we show that VO2 dipole antennas can be used to realize geometric phase coded metasurfaces for wave-front shaping and polarization rotation of THz waves. Moreover, we demonstrate that the corresponding efficiency of the THz spin Hall effect is closely related to VO2's THz electrical conductivity. In light of the dispersionless nature of the geometric phase, our study indicates that metasurfaces constructed by VO2 subwavelength resonators are good candidates for active control of broadband THz radiation.