Spin orientation and spin currents induced by linearly polarized light

To date, optical orientation of free-carrier spins and spin currents have been achieved by circularly polarized light, while the linearly polarized light has been used for optical alignment of electron momenta. Here we show that, in low-dimensional structures, absorption of the linearly polarized light also leads to the spin polarization and spin photocurrent, and, thus, the electron and hole spins can be manipulated by light of zero helicity. The microscopic description of the both effects is developed for interband optical transitions in undoped quantum wells (QWs) as well as for direct intersubband and indirect intrasubband (Drude-like) transitions in $n$-doped QW structures.