Quantum dot polarized light sources

The design, operation and performance of quantum dot spin-polarized vertical cavity surface emitting lasers (VCSELs) and single-photon sources are described and discussed. The effects of spin-induced gain anisotropy on output polarization and threshold current reduction have been studied along with the high-frequency response in a spin-polarized VCSEL. While the output circular polarization in a VCSEL follows the out-of-plane magnetization characteristics of the ferromagnetic spin injector, the output polarization of the spin-polarized single-photon source shows a switching behavior which is explained by invoking the exciton fine structure in the quantum dots and the effects of electron–hole exchange splitting due to in-plane quantum dot rotational asymmetry