  We show that the electron spin polarization generated by an electrical
current may have its direction controlled and magnitude amplified by periodic
optical excitation. The electrical and optical spin control methods were
combined and implemented in a two-dimensional electron gas. By Kerr rotation in
an external transverse magnetic field, we demonstrate unexpected long-lived
coherent spin oscillations of the current-induced signal in a system with large
spin-orbit interaction. Using a single linearly polarized pulse for spin
manipulation and detection, we found a strong dependence on the pulse optical
power and sample temperature indicating the relevance of the hole spin in the
electron spin initialization. The signal was mapped in a Hall bar as function
of the position relative to the injection contact. Finally, the presence of an
in-plane spin polarization was directly verified by rotating the experimental
geometry.
