Method and apparatus for generating and controlling spin propagation using one or more coherent light beams

A method of generating spin currents in a photoconductor material having a bandgap energy separating two energy bands, the method comprising the steps of:

• producing at least three coherent light beams of frequencies ω1, ω2, and ω3, such that ω1=ω2+ω3, polarizing each of said at least three coherent light beams to have a preselected polarization with respect to the other coherent light beams, at least ω1 having sufficient energy to excite charge carriers across the bandgap, and simultaneously irradiating a selected region of the photoconductor material with said at least three coherent light beams to generate a spin current in said photoconductor having a direction and magnitude determined by the relative polarization of said coherent light beams.

A method of generating spin currents in a photoconductor material which has a bandgap energy and non-centrosymmetric crystal symmetry, comprising the steps of:

• illuminating a photoconductor material having a non-centrosymmetric crystal symmetry with a coherent light beam having a pre-selected degree of elliptical polarization and an effective photon beam energy and effective intensity to optically excite charge carriers from one energy band across said bandgap into another energy band, thereby generating a spin current in said photoconductor having a direction and magnitude determined by the degree of polarization of said coherent light beam.