Regensburg 2013 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 71: Exciton polaritons and their condensates (HL, jointly with TT)

HL 71.1: Vortrag

Donnerstag, 14. März 2013, 09:30–09:45, H2

Polariton lasing in III-nitride based microcavities: How far are we from the Mott-transition? — •Georg Rossbach, Jacques Levrat, Etienne Giraud, Eric Feltin, Jean-Francois Carlin, Raphael Butte, and Nicolas Grandjean — ICMP, Ecole Polytechnique Fdérale de Lausanne, 1015 Lausanne, Switzerland

Non-equilibrium polariton condensates producing a coherent light source referred to as polariton laser have attracted a lot of interest as they should allow the realization of ultralow threshold coherent light-emitting devices due to the release of the population inversion condition. Polariton lasing under ambient conditions was demonstrated for the first time in a III-nitrid based microcavity, where the increased exciton stability and oscillator strength facilitate the strong coupling regime even for high carrier injection. Nevertheless, the generally observed emission energy blueshift toward the polariton lasing threshold indicates a significant altering of the light-matter coupling with increasing carrier density. Such non-linearities arise from the interacting excitonic fraction of cavity-polaritons.

Based on the investigation of the Mott-transition occurring in GaN/AlGaN single quantum wells and the microcavity bare active medium by means of non-resonant photoluminescence, the impact of the exciton renormalization on the polariton branch dispersion is discussed. Contrary to the usually assumed picture the exciton energy shift is shown to play a negligible role, while saturation effects emerging from phase space filling and exchange interaction govern the polariton renormalization already far below threshold.