TWO-PHOTON-ABSORPTION SPECTRA OF QUANTUM-WELL EXCITONS IN STATIC ELECTRIC FIELDS

We have measured two-photon-absorption spectra of GaAs/Al 0.4 Ga 0.6 As quantum-well structures in a static electric field for photon energies near half the band gap energy, and found drastic field-induced-changes in the spectra. The two-photon-absorption peak at half the energy of the lowest light-hole exciton is induced by the static electric field normal to the quantum well layers, in agreement with a theory that takes account of quasi-two-dimensional exciton effects. With increasing the electric field, however, this peak grows more drastically than the theoretical prediction, and it approaches a large value predicted by another simplified theory based on a two-level model.