Dynamic Terahertz Beamforming Based on Magnetically Switchable Hyperbolic Materials

TL;DR

This paper presents a novel method for dynamic terahertz beamforming using magnetically switchable hyperbolic materials, enabling active control of beam direction and polarization at 300 GHz.

Contribution

It introduces a metasurface design that utilizes magnetic fields to actively steer THz beams and demonstrates magnetic circular dichroism for tunable THz devices.

Findings

Beam tilting can be controlled by magnetic field magnitude and direction.

The proposed system achieves beam steering up to 45 degrees.

Magnetic circular dichroism enables magnetically tunable THz isolators.

Abstract

In this work, we introduce a concept to enable dynamic beamforming of terahertz (THz) wavefronts using applied magnetic fields (B). The proposed system exploits the magnetically switchable hyperbolic dispersion of the InSb semiconductor. This phenomenology, combined with diffractive surfaces and magnetic tilting of scattered fields, allows the design of a metasurface that works with either circularly or linearly polarized wavefronts. In particular, we demonstrate numerically that the transmitted beam tilting can be manipulated with the direction and magnitude of B. Numerical results, obtained through the finite element method (FEM), are qualitatively supported by semi-analytical results from the generalized dipole theory. Motivated by potential applications in future Tera-WiFi active links, a proof of concept is conducted for the working frequency f = 300 GHz. The results indicate that the transmitted field can be actively tuned to point in five different directions with beamforming of 45{\deg}, depending on the magnitude and direction of B. In addition to magnetic beamforming, we also demonstrate that our proposal exhibits magnetic circular dichroism (MCD), which can also find applications in magnetically tunable THz isolators for one-way transmission/reflection.