Dresden 2014 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 108: Poster: Ultra-fast phenomena / Optical properties / Semiconductor laser / Devices and device concepts

HL 108.9: Poster

Donnerstag, 3. April 2014, 17:00–20:00, P1

Time-resolved photo-ellipsometry studies of exciton-polaritons in a planar ZnO-based microcavity — •Steffen Richter, Chris Sturm, Helena Franke, Rüdiger Schmidt-Grund, and Marius Grundmann — Universität Leipzig, Institut für Experimentelle Physik II, Linnéstr. 5, 04103 Leipzig, Germany

Exciton-polaritons are composite quasi-particles which arise from strong coupling between excitons and photons. They inherit exciton spin as well as light polarization which both are expressed by means of the pseudospin of a polariton ensemble. The pseudospin is subject to various effective magnetic fields whereof one in particular can be related to population imbalances of polariton states with different pseudospin orientation.

We present investigations of the exciton-polariton pseudospin in a planar microcavity. The influence of the occupation of the lower polariton branch on the evolution of the eigenmode polarization is studied using pulsed laser excitation combined with time-resolved ellipsometry. Ellipsometry probes the density of states (DOS) while the combination with photoluminescence allows to deduce the dependence of the DOS on the states’ occupation. Furthermore, despite non-resonant excitation, the polarization of the laser can influence the occupation as well. The consequences are examined.

The planar microcavity consists of a λ/2 layer of ZnO with a slight thickness gradient. The splitting between the TE- and TM-polarized eigenmodes has values of up to 20meV for 37^∘ emission angle while the detuning between exciton and cavity photon energy is negative.