Unique prospects of graphene-based THz modulators

TL;DR

This paper demonstrates that graphene-based THz modulators can achieve over 90% modulation depth with minimal signal attenuation by tuning the Fermi level, offering a significant improvement over traditional 2DEG-based devices.

Contribution

The study introduces a graphene-based approach for THz modulation that surpasses the limitations of metal gates, enabling higher modulation depth and lower signal loss.

Findings

Achieved >90% modulation depth in graphene-based THz modulators.

Minimized signal attenuation to <5% using Fermi level tuning.

Demonstrated efficient electrostatic control of THz transmission.

Abstract

The modulation depth of 2-D electron gas (2DEG) based THz modulators using AlGaAs/GaAs heterostructures with metal gates is inherently limited to < 30%. The metal gate not only attenuates the THz signal (> 90%) but also severely degrades the modulation depth. The metal losses can be significantly reduced with an alternative material with tunable conductivity. Graphene presents a unique solution to this problem due to its symmetric band structure and extraordinarily high mobility of holes that is comparable to electron mobility in conventional semiconductors. The hole conductivity in graphene can be electrostatically tuned in the graphene-2DEG parallel capacitor configuration, thus more efficiently tuning the THz transmission. In this work, we show that it is possible to achieve a modulation depth of > 90% while simultaneously minimizing signal attenuation to < 5% by tuning the Fermi level at the Dirac point in graphene.