Optical coherent transient effects in semiconductor quantum wells exhibiting a two-hole species valence band

The paper deals with the detailed theoretical investigation of optical cohe rent transient processes in a narrow direct gap semiconductor quantum well structure (QWS), duly irradiated by a near band gap resonant ultrashort pul sed laser with moderate excitation intensity. The photoinduced band-to-band electronic transitions are considered from both the heavy-hole (hh) and li ght-hole (1h) valence hands to the lowest (Is) exciton state below the fund amental absorption edge. Since the hole populations in both hh and Ih bands are nontrivial in the case of the transverse plane in a QWS, we have recog nized that the hh and Ih excitons participate in photoinduced transitions. The photoinduced electron density is chosen to be less than the Mart densit y such that various many-body processes, otherwise significant, can be negl ected. The well-established time-dependent perturbation treatment of the se miconductor Bloch equations has been followed to calculate the induced pola rization as well as the differential transmission spectra. We find from the numerical estimates made for a GaAs/AlGaAs single QWS shined by a femtosec ond pulsed Ti:Sapphire laser that the transmission characteristics of the c oherent transient processes are dominated by the Ih species in the QWS. Rab i oscillation and Stark splitting as calculated for the two-hole species QW S agree qualitatively very well with recent experimental observations. (C) 2001 Academic Press.