I. Ya. Gerlovin

Nontrivial relaxation dynamics of excitons in high-quality InGaAs/GaAs quantum wells

Photoluminescence and reflectivity spectra of a high-quality InGaAs/GaAs quantum well structure reveal a series of ultranarrow peaks attributed to the quantum confined exciton states. The intensity of these peaks decreases as a function of temperature, while the linewidths demonstrate a complex and peculiar behavior. At low pumping the widths of all peaks remain quite narrow

Long-lived spin polarisation in the charged InP quantum dots

(l0.1\phantom{\rule{0.28em}{0ex}}\mathrm{meV})

Nuclear magnetic resonances in (In,Ga)As/GaAs quantum dots studied by resonant optical pumping

in the whole temperature range studied, 4\char21{}30 K. At the stronger pumping, the linewidth first increases and then drops down with the temperature rise. Pump-probe experiments show two characteristic time scales in the exciton decay,

Negative circular polarization of InP QD luminescence: Mechanism of formation and main regularities

l10\phantom{\rule{0.28em}{0ex}}\mathrm{ps}

Nonlinear optical dynamics of semiconductor nanostructures:: feasibility of the photonic quantum gate

and 15\char21{}45 ns, respectively. We interpret all these data by an interplay between the exciton recombination within the light cone, the exciton relaxation from a nonradiative reservoir to the light cone, and the thermal dissociation of the nonradiative excitons. The broadening of the low energy exciton lines is governed by the radiative recombination and scattering with reservoir excitons, while for the higher energy states the linewidths are also dependent on the acoustic phonon relaxation processes.

Coherent transients in semiconductor nanostructures as a basis for optical logical operations

Abstract This work is aimed at the investigation of the spin relaxation in controllably charged quantum dots (QDs). Measuring the dependence of the spin lifetime on the gate voltage in a heterostructure containing InP QDs, we detected the onset of spin conservation when the QD became negatively charged. The spin lifetime in the charged QDs exceeded 1 ns . Various properties of the long-lived spin polarisation of the QDs in longitudinal magnetic field as well as under various excitation conditions are discussed.

Dynamics of nuclear polarization in InGaAs quantum dots in a transverse magnetic field

The photoluminescence polarizations of (In,Ga)As/GaAs quantum dots annealed at different temperatures are studied as a function of external magnetic field (Hanle curves). In these dependencies, remarkable resonant features appear due to all-optical nuclear magnetic resonances (NMR) for optical excitation with modulated circular polarization. Application of an additional radio-frequency field synchronously with the polarization modulation strongly modifies the NMR features. The resonances can be related to transitions between different nuclear spin states split by the strain-induced gradient of the crystal field and by the externally applied magnetic field. A theoretical model is developed to simulate quadrupole and Zeeman splittings of the nuclear spins in a strained quantum dot. Comparison with the experiment allows us to uniquely identify the observed resonances. The large broadening of the NMR resonances is attributed to variations of the quadrupole splitting within the quantum dot volume, which is well described by the model.

Spin Quantum Beats in the Stokes Shifted Photoluminescence of InP Quantum Dots

The spectrum and kinetics of the circular polarization of InP quantum dot (QD) photoluminescence have been experimentally investigated under different conditions of optical excitation and at different bias voltages applied to the sample. It is established that, at a bias of about −0.1 V, the degree of photoluminescence polarization is negative and reaches −50% in limiting cases. It is concluded that the negative polarization is formed in QDs containing one recident electron per dot and is mainly caused by the optical orientation of the electron spin. It is shown that all experimentally observed regularities are well described in the framework of the model assuming the energy relaxation of photogenerated electron-hole pairs accompanied by the electron- hole spin flip-flop process.

Spin dynamics of quadrupole nuclei in InGaAs quantum dots

Abstract This paper is related to the modern branch of the nonlinear optics which is a search for and design of new media appropriate for the photonic information devices. We have studied experimentally a resonant nonlinear photoresponse of semiconductor nanostructure with GaAs/AlGaAs superlattice and determined the energy and phase relaxation rates of the free excitons in this structure. Theoretical analysis of resonant interaction of the coherent light pulses with quasi-two-dimensional nanostructure allowed us to conclude that such structures can be used for the fabrication of the photonic gates for quantum computer.

Multiple-frequency quantum beats of quantum confined exciton states

We propose an approach to realization of all-optical logical operations based on the nonlinear dynamics of an ensemble of two-level systems (TLSs) in a coherent photonic field. Using a theoretical analysis of the behaviour of a TLS ensemble in a resonant field, we formulate requirements for dynamic characteristics of a medium suitable for implementation of a photonic gate. Experimental studies of optical dynamics and excitonic state spectra of epitaxial GaAs/AlGaAs quantum wells and superlattices has allowed us to conclude that their physical parameters make it possible to build photonic-gate matrices exceeding the transistor-based electronic switches in terms of their productive capacity by five to six orders of magnitude.