Coherent all-optical polarization switching based on exciton-exciton interactions in quantum wells

A coherent all-optical nonlinear polarization switch based on exciton-excit on correlations is demonstrated in a multiple-quantum-well semiconductor st ructure. A contrast ratio of 8:1 and a relaxation time of less than a picos econd are reported at 80 K using only ten wells. The results are compared t o a simple phenomenological model to demonstrate that many-body effects are solely responsible for the switching action and that the turn-on and turn- off times are determined by the dephasing time. (C) 2001 American Institute of Physics.