Exact solution for surface wave to space wave conversion by periodical impenetrable metasurfaces

TL;DR

This paper presents an exact, lossless, and reciprocal surface impedance solution that fully converts a surface wave into a single free-space plane wave without evanescent modes, enhancing antenna efficiency.

Contribution

It introduces a novel impedance modulation design that ensures complete surface-to-space wave conversion while eliminating higher-order evanescent modes, unlike previous leaky-wave antenna approaches.

Findings

Achieves full conversion of surface wave to a single plane wave

Eliminates evanescent higher-order modes for maximum efficiency

Applicable across microwave to nanophotonics regimes

Abstract

We show that there exists an exact solution for a lossless and reciprocal periodic surface impedance which ensures full conversion of a single-mode surface wave propagating along the impedance boundary to a single plane wave propagating along a desired direction in free space above the boundary. In contrast to known realizations of leaky-wave antennas, the optimal surface reactance modulation which is found here ensures the absence of evanescent higher-order modes of the Floquet wave expansion of fields near the radiating surface. Thus, all the energy carried by the surface wave is used for launching the single inhomogeneous plane wave into space, without accumulation of reactive energy in higher-order modes. The results of the study are expected to be useful for creation of leaky-wave antennas with the ultimate efficiency, and, moreover, can potentially lead to novel applications, from microwaves to nanophotonics.