  We report the optical spectroscopic results of a single self-assembled
InAlAs/Al GaAs quantum dot. The polarization-dependent shift of the Zeeman
splitting in a single InAlAs QD has been observed. The induced Overhauser field
is estimated to be 0.16 T in this InAlAs QD and the magnitude is shown to be
controllable by the degree of circular polarization of excitation light.
