Spin-polarized electron emitter having semiconductor opto-electronic layer with split valence band and reflecting mirror

An electron emitting element comprising:

• a semiconductor opto-electronic layer having a split valence band, said opto-electronic layer emitting a beam of spin-polarized electrons from an emitting surface thereof upon incidence of an excitation laser radiation upon said emitting surface;
• a reflecting mirror formed on one of opposite sides of said opto-electronic layer remote from said emitting surface, said reflecting mirror reflecting said laser radiation and cooperating with said emitting surface to effect multiple reflection therebetween of said laser radiation;
• and
• a first semiconductor layer grown by epitaxy on said reflecting mirror and interposed between said reflecting mirror and said opto-electronic layer which serves as a second semiconductor layer,
• and wherein said first and second semiconductor layers have a lattice mismatch that causes said second semiconductor layer to be strained to give energy level splitting between a heavy-hole sub-band and a light-hole sub-band of said valance band, a distance between said emitting surface of said opto-electronic layer as said second semiconductor surface and said reflecting mirror being determined so as to permit resonance of said excitation laser radiation between said emitting surface and said reflecting mirror.