Regensburg 2019 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 39: Quantum dots and wires: Optical properties I

HL 39.4: Vortrag

Donnerstag, 4. April 2019, 10:15–10:30, H34

Exploring excited electronic states in QDs by spatially structured laser beams - a theoretical investigation — •Matthias Holtkemper, Doris E. Reiter, and Tilmann Kuhn — Institut für Festkörpertheorie, Universität Münster, Wilhelm-Klemm-Str. 10, 48149 Münster

In many experiments an optically driven self-assembled quantum dot (QD) is excited at some high energy. The created "hot" exciton relaxes via short-living intermediate levels into the exciton ground state which then decays radiatively. A detailed knowledge of the intermediate single and multiexciton levels is crucial to understand different relaxation channels as well as time-resolved nonlinear optical signals. However, many of the intermediate excitons are not optically accessible by standard Gaussian beams and, thus, difficult to study.

We theoretically explore the possibilities that arise by excitations with spatially structured light fields, such as higher modes in optical cavities or freely propagating Bessel or Hermite-Gaussian beams. We show that many of the intermediate states become accessible by such light fields. Furthermore, we show that the spatial degree of freedom of these laser fields can be used to excite different excitonic levels selectively. With this we propose a generalized polarization measurement, where not just the orientation of the dipole moments, but also the spatial orientation of the excitonic states can be measured.