  Circularly polarized optical excitation is used to demonstrate the efficient
injection of spin-polarized excitons to individual self-assembled CdSe quantum
dots in ZnSe barrier. The exciton spin-transfer is studied by means of
polarization-resolved single dot spectroscopy performed in magnetic field
applied in Faraday configuration. Detailed analysis of the neutral exciton
photoluminescence spectra reveals the presence of exciton spin relaxation
during its lifetime in a quantum dot. This process is seen for both nonmagnetic
dots and those containing single Mn$^{2+}$ ions. Taking this into account we
determine the spin-polarization degree of excitons injected to a dot under
circularly polarized below-the-barrier optical excitation at 488 nm. It is
found to be close to 40% in the entire range of the applied magnetic field.
Exploiting the established spin-conserving excitation channel we demonstrate
the optical spin orientation of a single Mn$^{2+}$ ion embedded in a CdSe/ZnSe
quantum dot.
