  In this paper we show that it is possible to switch the spin polarization of
the photocurrent signal obtained from a single self-assembled quantum dot
photodiode under the effect of elliptically polarized light by just increasing
the light intensity. In the nonlinear mechanism treated here, intense
elliptically polarized light creates an effective exchange interaction between
the exciton spin states through the biexciton state. This effect can be used as
a dynamical switch to invert the spin-polarization of the extracted
photocurrent. We further show that the effect persists in realistic ensembles
of dots, making this a powerful technique to dynamically generate
spin-polarized electrons.
