Interplay between polarization anisotropy and longitudinal spin relaxation in semiconductor quantum dots

We present a novel technique to study, in self-assembled quantum dots, the exciton spin longitudinal relaxation, which can be monitored under non-resonant excitation in contrast to the standard time-resolved techniques. We show that the magnitude of the polarization anisotropy of the photoluminescence signal, which arises from the different oscillator strengths of the two bright exciton states of the quantum dot, is a sensitive probe of the longitudinal relaxation of the exciton spin.