Graphene Based Terahertz Phase Modulators

TL;DR

This paper presents a novel graphene-based device that enables efficient electrical control of terahertz radiation's phase and amplitude, advancing high-resolution, noninvasive THz imaging technology.

Contribution

It introduces a new electrolyte-gated graphene device structure functioning as a tunable impedance surface for THz phase and amplitude modulation.

Findings

Voltage-controlled phase modulation of π achieved.

Reflection modulation of 50 dB demonstrated.

Multipixel phase modulator array successfully implemented.

Abstract

Electrical control of amplitude and phase of terahertz radiation (THz) is the key technological challenge for high resolution and noninvasive THz imaging. The lack of an active materials and devices hinders the realization of these imaging systems. Here, we demonstrate an efficient terahertz phase and amplitude modulation using electrically tunable graphene devices. Our device structure consists of electrolyte-gated graphene placed at quarter wavelength distance from a reflecting metallic surface. In this geometry, graphene operates as a tunable impedance surface which yields electrically controlled reflection phase. Terahertz time domain reflection spectroscopy reveals the voltage controlled phase modulation of {\pi} and the reflection modulation of 50 dB. To show the promises of our approach, we demonstrate a multipixel phase modulator array which operates as a gradient impedance surface.