Regensburg 2013 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 50: Exciton Polaritons and their Condensates (jointly with HL)

TT 50.4: Talk

Thursday, March 14, 2013, 10:15–10:30, H2

Polariton condensates in GaAs-based microcavities: influence of the spot size — •Matthias Salewski¹, Marc Aßmann¹, Jean-Sebastian Tempel¹, Franziska Veit¹, Sven Höfling², Martin Kamp², Alfred Forchel², and Manfred Bayer¹ — ¹Experimentelle Physik 2, Technische Universität Dortmund, 44221 Dortmund — ²Technische Physik, Physikalisches Institut, Universität Würzburg, 97074 Würzburg

Microcavity-polaritons consist of excitons strongly coupled to the photon field of the cavity. Photons leaking out of the cavity show the same energy-momentum dispersion as the polariton, which allows for easy experimental accessibility of the polariton states. It has been shown, that microcavity polaritons are able to undergo Bose-Einstein condensation.

Here, we investigated the influence of the excitation-spot size on the threshold carrier density necessary to create polariton condensates in a GaAs-based quantum-well microcavity. Different cavity-exciton detunings were examined.

By measuring the far-field emission of the cavity, we mapped the polariton dispersion relation as a function of the excitation power. Carriers were created by two excitation spots of different sizes. First, the intensity of the larger spot was varied. Second, while keeping the intensity of the larger spot fixed, the intensity of the second, much smaller spot was increased in the sub-milliwatt range. This way, we could measure the excitation efficiency of different spot sizes. Different results are observed for various detunings.