2D Material Microcavity Light Emitters: To Lase or Not to Lase?

Atomically thin layers of transition metal dichalcogenides (TMDs) are of great interest to the photonics community because of their unique optical properties. For example, in conjunction with microring or photonic crystal microresonators, they readily form microcavity light emitters. A number of configurations are now presented that apparently meet the conditions for lasing, yet there is considerable debate in the community as to whether lasing is actually achieved. By employing a very comprehensive set of assessment criteria, herein is shown that none of the TMD devices meet all the conditions for lasing, despite some very convincing data being presented. These findings are examined in the context of microcavity lasers based on III-V gain materials. Applications of TMD light emitters in the areas of quantum information and biosensing are also discussed to highlight areas where lasing action is not necessarily required.