We show theoretically how charge distribution in low-dimensional semiconductor heterostructures is manipulated and controlled by means of linearly polarized, strongly asymmetric electromagnetic pulses. In particular we point out the possibility of generating a charge polarization and charge currents in mesoscopic rings and how these non-equilibrium phenomena can be utilized as a source for electromagnetic radiation and for the generation of magnetic states in the rings. Possible relaxation and decoherence pathways are investigated by means of the density matrix formalism and typical time scales for the survival of the generated non-equilibrium charge distributions are estimated.
Properties of a new active optical medium, Er-doped SiO2 with silicon nanocrystals, are discussed. We have considered in detail the mechanism of excitation of erbium ions by quantum confined electron-hole pairs in silicon nanocrystals, the diffusion of excitation over the erbium ions inserted into the silicon dioxide matrix and the lifetime of erbium in the excited state limited by de-excitation cneters (traps, "black holes") in SiO2.