Abstract
Exciton magnetic polarons (EMPs) are self-organized magnetic quasiparticles that can be formed by excitons in diluted magnetic semiconductors (DMSs). The optical response of EMPs in DMS microstructures is not yet well understood because it is affected by many competing factors, including spin-dependent exchange interactions, phonon coupling, and collective and nonlinear effects upon the dopant concentration and structural relaxation. Here, we report on lasing from collective EMP states in Co(II)-doped CdS nanowires (NWs) and nanobelts (NBs) that we interpret in terms of bosonic lasing, the spontaneous emission of radiation by a single quantum state macroscopically populated by bosonic quasiparticles. The lasing threshold coincides with the appearance of ferromagnetic domains, indicating an important role of spin ordering in the formation of coherent collective EMPs. These results pave the way to the realization of a new type of bosonic laser, different from exciton-polariton lasers, where formation of the bosonic condensate is possible due to the coupling of EMPs via the exchange interaction of exciton and magnetic ion spins.