An InGaAs quantum well was made as a 2DEG (two dimensional electron gas) with structure inversion asymmtry (SIA). Rashba spin-orbit coupling in such a system was revealed by Shubnikov-de Haas (SdH) oscillation from its beating pattern. Two similar systems of different degree of SIA were measured to give a ratio of their Rashba coefficients to be about three.
                                                                                                              
Spin photocurrent was measured from these two samples by obliquely injected circularly polarized optical excitation. Photocurrent was induced in the 2DEG plane along the direction perpendicular to the orientation of the electron spin polarization which was resulted from the optical excitation. Conversely, current in the plane of the 2DEG can induce electron spin polarization oriented perpendicular to the current direction, and the spin can be detected by Kerr effect. Both of the two converesed effects are straightforward consequences of the Rashba spin-orbit coupling, and the ratios of the stength of the effects in the two samples are also in the order of three, in agreement with the SdH result.

Current induced electron spin polarization can be taken as a possible approach to create epin source for a spintronics device. Fruthermore, we have recently achieved converting a spin current is such a Rashba system into a measurable electric current, which is of great importance in spin detection or making the drain for a spin device, as proposed by Datta & Das.

Other curren approaches relevant to spintroincs devices will aslo be discussed.