I. Rumyantsev

On the identification of intervalence-band coherences in semiconductor quantum wells

A theoretical analysis of intervalence-band coherences is presented. These optically created non-radiative coherences are generalizations of non-radiative coherences in atomic and molecular three-level systems. Whereas in three-level systems these coherences are the basis of important and well-established nonlinear effects, the interpretation of experimental evidence for such coherences in semiconductors needs to be supported by many-body theory. Based on the dynamics-controlled truncation formalism, the respective contributions of intervalence-band coherences and coherent biexcitonic correlations in time-integrated differential transmission spectroscopy is investigated. It is found that the contribution of the biexcitonic correlations to the observable heavy-hole–light-hole beats can be eliminated, either by reducing the light pulse duration or by choosing the central frequency of the light pulses at the heavy-hole exciton.

Material and light-pulse parameter dependence of the nonlinear optical susceptibilities in the coherent χ (3) regime in semiconductor quantum wells

A detailed numerical study of the third-order nonlinear optical susceptibilities (χ(3)) of semiconductor quantum wells is presented. The dependence of χ(3) on material parameters (electron-hole mass ratio and exciton linewidths), on the light polarization configuration (co- and countercircularly polarized) and on the spectral configuration is discussed. The goal of this study is to map out the nonlinear phase shift per quantum well and a related figure of merit caused by quasi-resonant excitonic and biexcitonic nonlinearities induced by picosecond light pulses. The study is based on the dynamics-controlled truncation formalism and evaluated under the assumption that only 1s-heavy-hole excitons contribute to the nonlinearities. It includes all correlation effects (exciton–exciton scattering in the singlet and triplet channels and coherent biexciton formation in the singlet channel) that contribute within the coherent excitonic χ(3) regime.

Coherent control of AC spin currents based on excitation of continuum carriers

We show theoretically how electrical and pure spin AC currents can be optically injected in semiconductors via excitation of continuum carriers. The electrical current should be observable by detecting its THz radiation.

Optically injected AC spin currents based on excitonic quantum interference in semiconductors

We show theoretically how spin-polarized and pure spin AC currents can be optically injected in semiconductors via quantum interference between excitonic 1s and 2p states. The electrical current may be observed by its THz radiation.

The connection between phenomenological few-level models and microscopic theories in the nonlinear optics of semiconductors

We demonstrate a formal similarity between the evolution equation of the third-order interband polarization in a phenomenological model and that in microscopic theories for semiconductor optics, thereby providing a microscopic interpretation of the phenomenological model

Quantum kinetics of pure spin and charge currents

A quantum kinetic theory of scattering is applied to study the relaxation of optically-induced spin and charge currents in semiconductors. Even elastic scattering alone is shown to lead to pure spin current relaxation

Electromagnetically-induced transparency at the exciton resonance

We report the experimental demonstration of electromagnetically-induced transparency (EIT) in a GaAs quantum well, in which the absorption of an exciton resonance is reduced by more than twenty-fold. The destructive quantum interference for EIT is set up by a biexciton coherence.

Optically induced biexciton energy shift in semiconductor quantum wells

The energy level shift of a coherent biexciton (bound two-exciton state) in a semiconductor has been observed experimentally and analyzed theoretically. The shift, which results from the presence of excitons, can be related to the AC Stark shifts of the underlying exciton states.

Many-particle theory of all-optical polarization switching in semiconductor quantum wells

A microscopic many-body theory is used to analyze an all-optical polarization switching technique that has been demonstrated recently. The respective contributions of phase-space blocking and various exciton interaction and correlation terms to the switching process are calculated.

Evidence of nonperturbative exciton-exciton scattering in four-wave-mixing signals in quantum well microcavities

Summary form only given. The role of exciton-exciton scattering in the nonlinear optical response of semiconductor quantum wells is well established. However, an interesting question arising from the systems dimensionality has so far not been addressed. In the quantum theory of scattering in two dimensions, the scattering amplitude behaves non-smoothly and non-perturbatively at low energies. While the exact scattering amplitude vanishes as 1/ln (energy) as energy /spl darr/0, the second Born approximation diverges logarithmically. These properties result from the systems dimensionality and hold for any short-range well-behaved potential. One may ask whether the second Born approximation also fails for exciton-exciton scattering in two-dimensional structures and how this breakdown may be experimentally detected. In this contribution, we address this question within a microscopic theory of frequency-degenerate four-wave-mixing signals from a quantum-well microcavity. Analyzing an experiment reported in with this theory, we argue that the data are already sufficiently sensitive to show the breakdown of the second Born approximation for exciton-exciton scattering.