OPTICAL ORIENTATION AND ALIGNMENT OF EXCITONS IN QUANTUM DOTS

Optical orientation and alignment of excitons in InAlAs quantum dots i n the AlGaAs matrix have been studied both theoretically and experimen tally. Experiments performed in a longitudinal magnetic field (Faraday geometry) reveal transformation of optical orientation to alignment a nd alignment to orientation, which is caused by exchange splitting of the dipole-active exciton doublet and allowed by the quantum-dot low s ymmetry. A comparison of theory with experiment made with inclusion of the anisotropy of exciton generation and recombination along the [1 ( 1) over bar 1] and [110] axes permits one to determine the character o f dipole distribution in direction for resonant optical transitions in the self-organized quantum-dot ensemble studied. (C) 1998 American In stitute of Physics.