Milliwatt terahertz harmonic generation from topological insulator metamaterials

TL;DR

This paper demonstrates room-temperature terahertz third-harmonic generation from topological insulator Bi$_2$Se$_3$ structures, achieving milliwatt power levels and surpassing graphene performance, with potential for on-chip terahertz applications.

Contribution

It introduces a novel approach using topological insulator metamaterials for high-power terahertz harmonic generation at room temperature.

Findings

Third-harmonic power approaches milliwatts at 75 mW incident power.

Performance exceeds graphene by two orders of magnitude.

Surface states enable ultrafast heat dissipation and efficient harmonic generation.

Abstract

Achieving efficient, high-power harmonic generation in the terahertz spectral domain has technological applications, for example in sixth generation (6G) communication networks. Massless Dirac fermions possess extremely large terahertz nonlinear susceptibilities and harmonic conversion efficiencies. However, the observed maximum generated harmonic power is limited, because of saturation effects at increasing incident powers, as shown recently for graphene. Here, we demonstrate room-temperature terahertz harmonic generation in a Bi$_2$Se$_3$ topological insulator and topological-insulator-grating metamaterial structures with surface-selective terahertz field enhancement. We obtain a third-harmonic power approaching the milliwatt range for an incident power of 75 mW - an improvement by two orders of magnitude compared to a benchmarked graphene sample. We establish a framework in which this exceptional performance is the result of thermodynamic harmonic generation by the massless topological surface states, benefiting from ultrafast dissipation of electronic heat via surface-bulk Coulomb interactions. These results are an important step towards on-chip terahertz (opto)electronic applications.