Dissertation in the field of electrophysics, Osmo Vänskä
The title of thesis is Theoretical studies of optical transitions in semiconductor quantum structures
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This thesis presents work on modeling and creates new theoretical foundations for phenomena appearing in semiconductor quantum structures. Of special interest has been to generate a theoretical description to such phenomena that have been caused by an optical field and in which one sees changes, e.g., in angular momentum or spatial distribution of excited states. Basically, two kinds of structures are examined, quantum rings and wells. A quantum ring is a toroidal object of which volume is very small, but its diameter can be significant when compared to the wavelength of light. Another class of systems under study is a double quantum well structure, where there are two quantum wells on both sides of a tunnel barrier. In this system, the type-I and type-II semiconductor band-structure properties become combined in spatial coordinates, since the electrons and holes can occupy either the same or the separate quantum wells.
The two most interesting results are the angle-of-emission dependent photoluminescence from the quantum rings and the coherent control of vertical transport of desired quasiparticles through material interfaces in the quantum-well system in a selective manner. Since the obtained results on quantum rings are closely connected to the orbital-angular-momentum coupling between light and matter, they can prove to be important in different quantum information schemes where this angular-momentum aspect of light has been found to be highly beneficial. In quantum optics, there already are visible trends towards this direction. The predicted coherent control in a double-quantum-well system may mean a large technological progress, since by utilizing this effect one can study transport properties between materials over an interface, one of the most interesting examples of such phenomena being the transfer of quantum correlations through the interface without changing the local densities of electrons.
Opponent: Professor Antti-Pekka Jauho, Technical University of Denmark
Supervisor: Professor Ilkka Tittonen, Aalto University School of Electrical Engineering, Department of Micro- and Nanosciences
Electronic dissertation thesis (aaltolib.aalto.fi)
More information:
Osmo Vänskä
tel. +358 50 588 2979
osmo.vanska@aalto.fi