Optical orientation by linearly polarized light in intersubband quantum-well transitions

The absorption of linearly polarized light in low-dimensional semiconductor structures is investigated. It is shown that the absorption under consideration can give rise to spin orientation of free carriers. A theory of this optical orientation by linearly polarized light is developed for resonant intersubband optical transitions in n-type quantum wells. It is demonstrated that, in the vicinity of the resonance, the optical orientation undergoes spectral inversion, namely, the electron spin orientation reverses sign with increasing frequency. This behavior can be accounted for by the spin-orbit subband splitting, which is linear in the wave vector, and by the energy and quasi-momentum conservation laws.