Terahertz spoof surface plasmonic demultiplexer based on band-stop waveguide units.

Demultiplexers play an important role in wavelength division multiplexing optical transmission systems and constitute an essential component of future terahertz integrated circuits. In this work, we propose a terahertz spoof surface plasmonic demultiplexer, which is capable of distinguishing between three different frequencies by exploiting the band-stop effect of the waveguide units. The waveguide units are composed of metallic pillars of different sizes, where the transmission of spoof surface plasmons in the terahertz range is strongly influenced by the pillar size. The frequency-splitting feature can be achieved by selecting waveguide units with proper parameters that allow the passbands of the waveguides to be completely non-overlapping. As the effective working section, the length of the band-stop units is 1 mm, and extinction ratios of 21.5 dB, 18.0 dB, and 23.9 dB are obtained at 0.578 THz, 0.632 THz, and 0.683 THz, respectively. The proposed band-stop unit and its tunable characteristics have important applications for further development of terahertz integrated communication systems and terahertz on-chip plasmonic circuity.