Abstract

The nonlinear behavior of near-bandgap electronic excitations in semiconductors is dominated by anharmonicities in exciton-exciton and exciton-photon interactions which depend critically on dimensionality¹. Upon application of a magnetic field perpendicular to quantum wells, the constant density of states above bandgap becomes singular in the discrete spectrum of the magneto-exciton (Coulomb correlated Landau levels). At very high magnetic fields, the size of the in-plane wavefunctions is reduced to less than the excitonic Bohr radius, so that the states are strongly confined in all three dimensions. Investigation of the nonlinear optical response of such systems allows measurement of the exciton-exciton and exciton-photon interactions within and between magneto-exciton states in the quasi-zero dimensional limit. We report the first observation of femtosecond time resolved optical nonlinearities in quasi-zero-dimensional magneto-excitons at fields up to 12 T, and at cryogenic temperatures.

© 1990 Optical Society of America