All‐Dielectric Metasurface‐Based Gap Waveguides

The development of modern optical communication systems requires specific waveguides, given that the widely used fiber‐optic components are poorly integrated with planar technologies. For planarization in the millimeter‐wave and subterahertz bands, so‐called gap waveguides are proposed, offering low‐loss performance and cost‐efficient manufacturing. Hence, the utilization of this technology in the optical range is very promising. Herein, a strategy for designing gap waveguides made of two metasurfaces composed of dielectric disk‐shaped resonators operated in hybrid HE (magnetic dipole) and EH (electric dipole) modes is proposed. The coupled dipole model is applied to the complex multiple‐scattering problem by substituting each resonator as an electric and magnetic dipole, providing equations for the efficient calculation of metasurface reflection and transmission properties. It is demonstrated that with the correct choice of metasurface geometry providing their resonant reflection conditions, a waveguide channel can be implemented between a pair of metasurfaces, which allows propagation of the transverse electric and transverse magnetic waves similar to those of a parallel plate waveguide with perfectly conducting either electric or magnetic walls. This approach may be seen as a novel metasurface‐based waveguide structure that uses flexibly mediated boundary conditions to control electromagnetic wave propagation.