Ultrafast optical nonlinearity by virtual charge polarization in DC-biased quantum well structures

An optical nonlinearity due to virtual charge polarization in a quantum-well structure biased by a DC electric field is proposed and discussed. The switching time of the nonlinearity is expected to be extremely short, on the order of 100 fs. An effective degenerative four-wave chi /sup 3/ parameter is estimated to be 1.0*10/sup -9/ (esu) for a graded gap AlGaAs quantum well and a detuning energy of pump light, 35 meV. The nonlinearity is observable and quite useful for designing an all-optical and ultrafast optical gate.<
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