One-Dimensional Spoof Surface Plasmon Structures for Planar Terahertz Photonic Integration

The waveguiding properties of spoof surface plasmon modes propagating along three kinds of one-dimensional groove arrays composed of V-shaped, rectangular, and trapezoid grooves, respectively, are numerically investigated. The results show that the trapezoid groove array demonstrates a tighter confinement compared to the other two groove arrays with the same groove opening. The propagation loss of the three structures at the same frequency are analyzed, from which it is concluded that the propagation loss of spoof plasmon waveguides is determined not only by the difference between the operation frequency and asymptotic frequency but also by the loss associated with the TEM mode inside individual grooves. The bending loss through small bending radii of the three structures (~0.5λ) is also calculated showing that although the straight trapezoid groove array exhibits highest propagation loss, the transmission loss through a 90° bend of it is lower resulting from the tighter confinement than that of the other two groove array bends having the same radius. This property together with the ease of fabrication makes the trapezoid structure a better candidate for planar terahertz photonic integration on the subwavelength scale.