Dresden 2011 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 38: Polaritons and Polariton Lasing
HL 38.5: Talk
Tuesday, March 15, 2011, 13:00–13:15, FOE Anorg
Balistic exciton polariton propagation in CdZnTe crystals — •Tillmann Godde1, Ilya Akimov1, Dimitri Yakovlev1, Henri Mariette2, and Manfred Bayer1 — 1Experimentelle Physik 2a, Technische Universität Dortmund, 44227 Dortmund, Germany — 2CEA-CNRS group Nanophysique et Semiconductors, Institute Néel, CNRS and Université Joseph Fourier, 25 Avenue des Martyrs, 38042 Grenoble, France
We study the propagation of lower branch exciton polaritons in 200 µm - 800µm thick Cd0.88Zn0.12Te samples using time resolved photoluminescence (PL) and time of flight techniques. The PL spectrum comprises of two peaks consistent with emission from upper and lower polariton branches with a resonance frequency of ℏ ω0 = 1.664 eV. The lifetimes of the exciton polaritons in the upper and lower branches are 1.5 ns and 3 ns, respectivly.
In time of flight measurements we observe significant delay of 1 ps optical pulses, which increases to 350 ps at ℏ ω= 1.661 eV in a 745 µm thick sample. Femtosecond-pulses get stretched and allow to obtain the dispersion in a single streak camera measurement. We reproduce the measured delays using a single oscillator model for the lower polariton branch dispersion.
The propagation is ballistic, which follows from the observation of reflected replica pulses. Assuming that the exciton polariton scattering on optical and acoustical phonons is mainly inelastic, we conclude that the propagation is coherent. We estimate the coherence time to be about 300 ps.