In-Plane Focusing of Terahertz Surface Waves on a Gradient Index Metamaterial Film

TL;DR

This paper presents a gradient index metasurface that effectively focuses terahertz surface waves in-plane, achieving a small focal spot and significant field enhancement, advancing terahertz wave manipulation techniques.

Contribution

The study introduces a novel gradient index metasurface design for in-plane focusing of terahertz surface waves with experimental validation.

Findings

Surface waves focused to 500 μm diameter

Field amplitude increased by a factor of 3 at focus

Focal length approximately 2 mm

Abstract

We designed and implemented a gradient index metasurface for the in-plane focusing of confined terahertz surface waves. We measured the spatial propagation of the surface waves by two-dimensional mapping of the complex electric field using a terahertz near-field spectroscope. The surface waves were focused to a diameter of 500 \micro m after a focal length of approx. 2 mm. In the focus, we measured a field amplitude enhancement of a factor of 3.