Polarization conversion of excitonic photoluminescence under zero and nonzero magnetic fields in single InAlAs quantum dots

We demonstrated the circular to linear polarization conversion in single InAlAs/AlGaAs QDs. Since the anisotropic exchange interaction acts on the photo-created exciton spin as an in-plane effective magnetic field, the polarization of emissions can be converted from circular to linear and vice versa even under a zero external magnetic field. By using the quasi-resonant excitation, high conversion ratio up to ∼50% was obtained under nonzero longitudinal magnetic field. Additionally, exciton spin relaxation time and built-in linear dichroism were estimated by exciton spin dynamics in the 3D pseudospin precession model.