Ultrafast optical spectroscopy enables us
to measure the dynamics of photoexcited free carriers and excitons on the time
scale of hundreds of femtoseconds. In low dimensional semiconductor
nanostructures such as quantum wire and quantum dot, novel many-body effects
involved with Coulomb interaction, exchange and correlation effect are of
fundamental interest. In addition, the strong coupling of light to excitons
produces a nonlocal dielectric response of the crystal, the spatial dispersion
being mediated by the polariton. The optical nonlinearities of exciton-polariton
has a great potential in optoelectronic devices, and coherent manipulation of
the excitonic quantum state is a building block of quantum information &
computation technology.
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