Prospects and limitations of transition-metal dichalcogenide laser gain materials

TL;DR

This paper investigates the potential of transition-metal dichalcogenide monolayers as laser gain materials, highlighting their high efficiency and the limitations imposed by band-structure changes at high excitation levels.

Contribution

It provides microscopic gain calculations for TMD monolayers, revealing the effects of carrier-induced band-structure renormalizations on laser feasibility.

Findings

High quantum efficiency of TMD monolayers as gain materials

Band-structure renormalization causes a direct-to-indirect band-gap transition

Gain rollover limits the excitation regime for lasing

Abstract

Nanolasers operate with a minimal amount of active material and low losses. In this regime, single layers of transition-metal dichalcogenides (TMDs) are being investigated as next generation gain materials due to their high quantum efficiency. We provide results from microscopic gain calculations of highly excited TMD monolayers and specify requirements to achieve lasing with four commonly used TMD semiconductors. Our approach includes band-structure renormalizations due to excited carriers that trigger a direct-to-indirect band-gap transition. As a consequence, we predict a rollover for the gain that limits the excitation regime where laser operation is possible. A parametrization of the peak gain is provided that is used in combination with a rate-equation theory to discuss consequences for experimentally accessible laser characteristics.