Reconfigurable terahertz stretchable spoof surface plasmon polariton waveguide for filter applications

Abstract

In this paper, a reconfigurable terahertz spoof surface plasmon polariton (SPP) waveguide is proposed on a stretchable polydimethylsiloxane (PDMS) substrate. The SPP unit incorporates a folded stub and a conventional V-shaped SPP groove, enhancing the equivalent capacitance and consequently reducing the cutoff frequency. The cutoff frequency of the proposed SPP unit can be tuned from 285 to 390 GHz with stretchable factors of 1 ∼ 1.2, thereby achieving a reconfigurable operating frequency. The horizontal dimension of the proposed SPP waveguide can be tuned from 6.36 mm to 7.12 mm. Moreover, the SPP waveguide can generate transmission continuous phase shifts of −30°, −60°, −90°, and −120° with stretchable factors of 1.05, 1.1, 1.15, and 1.2, respectively, in the 150–190 GHz band. Applying the characteristic mode theory, a split ring resonator (SRR) functions as the equivalent magnetic dipole, which remains unaffected by stretchable deformation. When loaded with four SRR cells, the proposed SPP waveguide generates a tunable passband with a fixed notched frequency at 193 GHz. Another stretchable SPP resonator serves as the equivalent electric dipole, operating from 284 GHz to 256 GHz in 1∼1.2 stretchable states. By loading three SPP resonators, the SPP waveguide can achieve a passband for the initial state, and a tunable stopband is introduced under 1.1 and 1.2 stretchable states. The proposed stretchable method provides a promising solution for planar terahertz components and systems with reconfigurable functions.