Room temperature electrically tunable broadband terahertz Faraday effect

TL;DR

This paper demonstrates a room temperature, electrically tunable, broadband Faraday effect in HgTe, enabling high-speed modulation of terahertz radiation for advanced scientific and technological applications.

Contribution

It introduces a novel approach for electrically controlling the Faraday effect in HgTe at room temperature across a broad THz range, using the field effect in a thin semimetal film.

Findings

Giant Faraday effect observed in HgTe at room temperature.

Electrical tuning achieved over 0.1-1 THz frequency range.

Potential for high-speed THz modulation applications.

Abstract

The terahertz (THz) frequency range (0.1-10 THz) fills the gap between the microwave and optical parts of the electromagnetic spectrum. Recent progress in the generation and detection of the THz radiation has made it a powerful tool for fundamental research and resulted in a number of applications. However, some important components necessary to effectively manipulate THz radiation are still missing. In particular, active polarization and phase control over a broad THz band would have major applications in science and technology. It would, e.g., enable high-speed modulation for wireless communications and real-time chiral structure spectroscopy of proteins and DNA. In physics, this technology can be also used to precisely measure very weak Faraday and Kerr effects, as required, for instance, to probe the electrodynamics of topological insulators. Phase control of THz radiation has been demonstrated using various approaches. They depend either on the physical dimensions of the phase plate (and hence provide a fixed phase shift) or on a mechanically controlled time delay between optical pulses (and hence prevent fast modulation). Here, we present data that demonstrate the room temperature giant Faraday effect in HgTe can be electrically tuned over a wide frequency range (0.1-1 THz). The principle of operation is based on the field effect in a thin HgTe semimetal film. These findings together with the low scattering rate in HgTe open a new approach for high-speed amplitude and phase modulation in the THz frequency range.