Nonlinear optical response of 2-D magnetoexcitons

Initial results of a numerical study of the coherent nonlinear optical response of 2-D excitons in a strong perpendicular magnetic field are presented. By solving the semiconductor density matrix equations in a Landau basis (with up to 1700 orbitals), the response of the system to pump and probe pulses of various durations, excitation wavelengths, and intensities has been calculated. This includes both the nonlinear probe absorption as well as the two-pulse self-diffraction (four-wave mixing) signal generated parametrically. The results show that (inter-Landau level) Coulomb interactions generally persist up to the highest magnetic fields, giving rise to pronounced many-body effects in the nonlinear optical response. Time-resolved nonlinear absorption spectra for a cyclotron frequency equal to 16-Ry E₀ and the corresponding time-integrated two-pulse self-diffracted signal for R = 3E₀ are shown and discussed.