Propagation-invariant channels on terahertz metasurfaces with hyperbolic dispersion

We report the implementation of split-ring resonator (SRR) metasurfaces with hyperbolic dispersion that allow spoof surface-plasmon polaritons (SSPPs) to propagate on diffraction-free in-plane paths. We use these propagation-invariant channels to sustain a confined propagation of terahertz SSPPs within the metasurface. By changing the location of the SRR-gap, the propagation angle of the SSPP can be tuned, additionally allowing for arbitrary in-plane routing.