  We demonstrate a new method of measuring the exciton spin relaxation time in
semiconductor nanostructures by continuous-wave photoluminescence. We find that
for self-assembled CdTe quantum dots the degree of circular polarization of
emission is larger when exciting polarized excitons into the lower energy spin
state than in the case when the excitons are excited into the higher energy
spin state. A simple rate equation model gives the exciton spin relaxation time
in CdTe quantum dots equal to 4.8+/-0.3 ns, significantly longer than the
quantum dot exciton recombination time 300 ps.
