Dresden 2003 – wissenschaftliches Programm

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HL: Halbleiterphysik

HL 41: Quantenpunkte und -dr
ähte: Optische Eigenschaften II

HL 41.9: Vortrag

Donnerstag, 27. März 2003, 13:00–13:15, POT/81

Cascaded emission of strongly polarization-correlated photon pairs from CdSe/ZnSe quantum dots — •S. Ulrich¹, S. Strauf¹, P. Michler¹, G. Bacher², and A. Forchel² — ¹Institut für Festkörperphysik, Universität Bremen — ²Technische Physik, Universität Würzburg

We investigated the photoluminescence (PL) of single self-assembled CdSe/ZnSe quantum dots (QDs) at T = 4 K with special regard to the polarization properties of the emission. An analysis of biexcitonic(XX)/excitonic(X) PL revealed a characteristic doublet structure showing a pronounced linear polarization anisotropy. According to theory, this behaviour clearly reflects a reduced QD symmetry <D_2D. The photon emission statistics was studied under non-resonant pulsed excitation. Autocorrelation measurements performed on paired XX/X PL lines revealed strong evidence for triggered single-photon emission from both these radiative decay channels. From XX-X cross-correlation measurements we found a high PL correlation degree of 74.5 % in terms of collinear polarization, which is attributed to the QD asymmetry. The cross-correlation traces were interpreted with regard to the radiative XX/X lifetimes obtained from time resolved PL. From the cross-correlation traces obtained under perpendicular polarization an estimate for the spin relaxation time t_spin between the two non-degenerate bright X states could be made.