Highly efficient terahertz generation using 3D Dirac semimetals

TL;DR

This paper demonstrates that 3D Dirac semimetals, especially Cd3As2, can achieve extremely high optical-to-terahertz conversion efficiencies, surpassing traditional materials by large margins, and offers insights into tuning efficiency via Fermi energy.

Contribution

The study predicts and analyzes the high efficiency of terahertz generation in 3D Dirac semimetals, highlighting their potential for ultrathin, compact terahertz sources, a significant advancement over existing materials.

Findings

Cd3As2 exceeds LiNbO3 in efficiency by >5000 times at nanoscale distances.

Efficiency remains high across various input frequencies, field strengths, and temperatures.

Fermi energy tuning enables step-like increases in conversion efficiency.

Abstract

We show that 3D Dirac semimetals are promising candidates for highly efficient optical-to-terahertz conversion due to their extreme optical nonlinearities. In particular, we predict that the conversion efficiency of Cd3As2 exceeds typical materials like LiNbo3 by >5000 times over nanoscale propagation distances. Our studies show that even when no restrictions are placed on propagation distance, Cd3As2 still outperforms LiNbo3 in efficiency by >10 times. Our results indicate that by tuning the Fermi energy, Pauli blocking can be leveraged to realize a step-like efficiency increase in the optical-to-terahertz conversion process. We find that large optical to terahertz conversion efficiencies persist over a wide range of input frequencies, input field strengths, Fermi energies, and temperatures. Our results could pave the way to the development of ultrathin-film terahertz sources for compact terahertz technologies.