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My proposed research is to investigate the optical injection of spin current in semiconducting structures of reduced dimensionality.
Using two laser pulses of frequencies ω and 2ω, it is possible to sort injected carriers according to their spin. Electrons within the sample can be excited by either two-photon absorption of the fundamental frequency or one-photon absorption of the second harmonic. Spin separation is a result of quantum interference between the two equivalent pathways. Coherent control of the resulting spin current can be achieved by parameters of the optical fields.
Optical injection and coherent control of spin current has been studied in bulk (3D) and quantum wells (2D). It is expected that spin currents can also be produced in structures like quantum wires (1D). Reduced dimensionality means more control over the motion of the injected spins.
Just like charge in electronics, spin is another degree of freedom of matter which can be used to carry information. A major problem facing the development of “spintronics” is the difficulty to control spin in a coherent manner. In the long term, this research could see the development of spin-based information technology.
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