# High-efficiency terahertz spin-decoupled meta-coupler for spoof surface plasmon excitation and beam steering

## TL;DR

This paper introduces a novel terahertz spin-decoupled meta-coupler that efficiently excites spoof surface plasmons and enables beam steering, overcoming previous limitations related to spin coupling in circular polarization devices.

## Contribution

The study designs and numerically demonstrates a bifunctional meta-coupler capable of spin-decoupled SSP excitation and beam steering at terahertz frequencies, with high conversion efficiencies.

## Key findings

- Achieves 82% and 70% conversion efficiency for right and left circular polarizations at 0.3 THz.
- Enables polarization-controlled SSP excitation and beam steering.
- Allows integration of multiple functionalities through phase distribution adjustments.

## Abstract

Spoof surface plasmon (SSP) meta-couplers that efficiently integrate other diversified functionalities into a single ultrathin device are highly desirable in the modern microwave and terahertz fields. However, the diversified functionalities, to the best of our knowledge, have not been applied to circular polarization meta-couplers because of the spin coupling between the orthogonal incident waves. In this paper, we propose and numerically demonstrate a terahertz spin-decoupled bifunctional meta-coupler for SSP excitation and beam steering. The designed meta-coupler is composed of a coupling metasurface and a propagating metasurface. The former aims at realizing anomalous reflection or converting the incident waves into SSP under the illumination of the left or right circular polarization waves, respectively, and the latter are used to guide out the excited SSP. The respective converting efficiency can reach 82% and 70% at 0.3THz for the right and left circular polarization incident waves. Besides, by appropriately adjusting the reflection phase distribution, many other diversified functionalities can also be integrated into the meta-coupler. Our study may open up new routes for polarization-related SSP couplers, detectors, and other practical terahertz devices.

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Source: https://tomesphere.com/paper/1904.06133