Polarization dependence of four-wave-mixing signals in quantum wells

Abstract

Recent transient four-wave-mixing experiments in the two-pulse photon-echo configuration performed on GaAs quantum wells have yielded the surprising result that in some samples the T2 time obtained from the polarization decay can be shorter for cross-polarized input fields than for parallel input fields. A concomitant change from photon-echo to free-induction-decay behavior has also been observed. A phenomenological model is presented which explains these observations by means of a disorder-induced coupling of the o. + and o. exciton transitions which is inhomogeneous in coupling strength. Such coupling also leads to a remarkable change in the light-holeheavy-hole exciton quantum beat phase as a function of pulse delay for a critical relative orientation of the polarization of the incident pulses. Experimental observations of this efFect are presented to support the validity of the model.

Polarization-dependent quantum beats of four-wave mixing in the Luttinger model for bulk semiconductors

“…In view of the various approximations made, this is in remarkable agreement with the observations in Ref. 2 All these features seen in experiments are reflected in Eq. ͑23͒ without invoking other mechanisms than just the coupling of the carrier ͑polarization͒ dynamics with the light fields.…”

“…͑23͒ show three features that are also observed in experiment. 2 Firstly, the FWM signal is stronger in the case of parallel polarization than in case of cross polarization by roughly a factor of 5, in good agreement with the experiment of Bennhardt et al 2 and in contrast to earlier theoretical expressions, 1 which predicted equal strength in both cases. Secondly, we do indeed find a beat behavior as a function of the delay time which has a maximum at zero delay time for the case of parallel polarization and an opposite oscillating behavior for orthogonal polarization.…”

“…This phenomenon has been analyzed by applying semiconductor Bloch equations ͑SBE͒ for excitations in a six-band model with broad spectrum pump-probe pulses. 1,2 These theoretical studies did not reproduce essential details of the observations. For instance, they predicted identical FWM intensities for the two cases: pump and probe having either parallel or perpendicular linear polarizations.…”

“…Polarization-dependent four-wave mixing ͑FWM͒ quantum beats [1][2][3][4][5][6][7][8][9][10][11] have been observed after simultaneous excitations of two optical transitions, associated with heavy hole and light hole. The signal magnitude and its beat phase were found to depend on the relative linear polarization of the pump and test pulses.…”

Coherent optical nonlinearities and phase relaxation of quasi-three-dimensional and quasi-two-dimensional excitons inZnSxSe1−xWägner1, Schätz2, Maier3 et al. 1997Phys. Rev. B354110View full textAdd to dashboardCite

“…In particular, FWM provides an experimental approach for the investigation of quantum beat phenomena [1][2][3][4][5] and scattering processes of excitons with free carriers, [6][7][8] excitons, [9][10][11][12] and phonons. 10,[13][14][15] The underlying physics is approximately described by the optical Bloch equations.…”