Valence-band mixing and photon echo in semiconductor quantum wells

Sheetal Kapoor, Pratima Sen, Pranay K. Sen

Yiping Z. Hu, Rolf H. Binder, S. W. Koch

The coherent optical response of semiconductor quantum wells is studied theoretically using the multiband semiconductor Bloch equations which include coupling of the heavy- and light-hole bands as well as many-body Coulomb effects. For the case of a two-pulse excitation scheme it is shown how the different rotational symmetries of heavy- and light-hole bands induce a strong polarization dependence of the signal in the photon echo direction. The selection rules are based on the Kane-Luttinger theory while the transition amplitudes are obtained by numerically solving the multiband semiconductor Bloch equations. In addition, the influence of valence-band mixing effects on the optical Stark effect is demonstrated.

Philippe M. Fauchet

Philippe M. Fauchet

Sheetal Kapoor, Pratima Sen, Pranay K. Sen

We have studied optical nutation and Stark splitting in a GaAs/AlGaAs quantum well with multi valence band structure using effective semiconductor Bloch equations. The individual roles of light and heavy holes in optical nutation have been examined. The analysis shows that both Rabi oscillation frequency and Stark splitting increase with rising electric field strength as observed experimentally. Also it is seen that light hole species dominates over heavy hole species in the transmission characteristics of quantum wells.

T. Dekorsy, A. M. T. Kim, G. C. Cho +5 more

Quantum beats of heavy and light holes in GaAs quantum wells are investigated in femtosecond time-resolved four-wave mixing and transmission experiments as a function of optical excitation energy. Under nonexcitonic excitation conditions, the four-wave mixing signal disappears due to the immediate loss of the interband coherence of continuum states. In the transmission experiment, the quantum beats are observed up to excess energies of 75 meV above the exciton resonances. The experimental data clearly demonstrate the coherence of continuum states in the valence band. Changes of the beat frequency with the excitation energy are due to the dispersion of the valence bands.