Abstract-Terahertz broadband spoof surface plasmon polaritons using high-order mode developed from ultra-compact split-ring grooves

Kai-Da Xu, Ying Jiang Guo, and Xianjin Deng

Fig. 1 Schematic configuration of the proposed THz SSPP unit cell. (a) Slotline with two-side transversal grooves (Structure A). (b) Grounded slotline with two-side transversal grooves (Structure B). (c) Grounded slotline with two-side split-ring grooves (Structure C). The detailed dimensions are D = 20 µm, L2 = 36.2 µm, L3 = 43 µm, W0 = 1.5 µm, W1 = 1 µm, W2 = 220 µm, W3 = 75.9 µm, W4 = 12.5 µm, W5 = 1 µm, and W6 = 1 µm. (d) Dispersion curves of the fundamental and high-order modes of different SSPP unit cells. The inset is the z-component electric field distributions of the first two modes of the Structure C unit cell.

https://www.osapublishing.org/oe/abstract.cfm?uri=oe-27-4-4354

Terahertz (THz) broadband spoof surface plasmon polaritons (SSPPs) using new structure of ultra-compact split-ring grooves are proposed. The high-order mode propagation is highly concentrated around the proposed structure with lower radiation loss implying improved operating bandwidth. More importantly, a size reduction of 83.5% can be realized as compared to the traditional grounded SSPP structure with the same high-order asymptotic frequency. To further verify the proposed idea, a similar structure in microwave regime is designed and measured, where the excitation is easily achieved by directly connecting the microstrip line to the proposed SSPP waveguide. The gradient transition section, such as flaring ground, can be avoided, which decreases the waveguide’s longitudinal and transversal lengths and simplifies the design procedure. The measured results of the microwave prototype illustrate that it has good lowpass filtering performance, in which the reflection coefficient is better than −10 dB up to 13 GHz, with the smallest and worst insertion losses of 0.5 dB and 4.5 dB, respectively. To the best of the authors’ knowledge, this work presents THz high-order broadband SSPP propagation for the first time, having significant potential for plasmonic integrated circuits application at microwave/THz frequencies.

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