http://www.rdmag.com/news/2015/10/exciting-breakthrough-2-d-lasers
Among the most talked about class of materials in the world of nanotechnology today are 2-D transition metal dichalcogenides (TMDCs). These 2-D semiconductors offer superior energy efficiency and conduct electrons much faster than silicon. Furthermore, unlike graphene, the other highly touted 2-D semiconductor, TMDCs have natural bandgaps that allow their electrical conductance to be switched "on and off," making them more device-ready than graphene. Tungsten disulfide in a single molecular layer is widely regarded as one of the most promising TMDCs for photonic and optoelectronic applications. However, until now, coherent light emission, or lasing, considered essential for "on-chip" applications, had not been realized in this material. In a previous study, Zhang and his research group had developed a "whispering gallery microcavity" for plasmons, electromagnetic waves that roll across the surfaces of metals. Based on the principle behind whispering galleries-where words spoken softly beneath a domed ceiling can be clearly heard on the opposite side of the chamber-this micro-sized metallic cavity for plasmons strengthened and greatly enhanced the Q factor of light emissions. In this new study, Zhang and his group were able to adapt this microcavity technology from plasmons to excitons-photoexcited electrons/hole pairs within a single layer of molecules.
